Installing durable and level floors is one of the most important issues when building a house or when renovating an apartment. Homeowners have a wide range of options these days. There is a very wide range of different building mixtures on sale on a mineral or synthetic basis, allowing you to quickly and efficiently fill a flat surface, which will either serve as the basis for laying any finishing coating, or will itself act as a floor. However, many owners still prefer to make floors using time-tested technology - with the installation of planks or other coverings on logs.
Of course, modern technologies have affected this type of flooring, however, basic principles their devices remain unchanged for perhaps centuries. It is simplicity and reliability that make this design extremely popular in our time. And what is very important is that probably any home craftsman can make and install floor joists with his own hands if he is careful and attentive, follows the instructions, mobilizes his skills and has high-quality materials and the necessary working and control tools.
What are lags and the benefits of using them
First of all, what are lags? These are cross beams, which serve as the basis for attaching floorboards or other sheet flooring material to them. The traditional material for making logs has always been wood, although construction technologies also allow the use of metal, concrete or polymer parts. However, this is rather an exception to the rule, and non-wooden logs will not be considered within the framework of this article.
Traditional material for logs is wooden beams
The design of wooden logs also varies. The most convenient thing to use, of course, is a flat wooden beam “trimmed” to the required size - with it both assembly and setting the required level is much easier. You can also use boards, placing them on edge and, if necessary, selecting the required thickness of the log from several interconnected parts. in some cases, it is more profitable for builders to use rough wood to make beams, however, this will require at least trimming it On the one side– for a tight fit of floorboards or counter battens.
Wood may be inferior in some ways to cement coating, but, nevertheless, the construction of the floor on logs provides many significant advantages:
- First of all, with the same height of the floor, a structure with logs is incomparably lighter than concrete, even if lightweight compounds with insulating fillers are used.
- When assembled correctly, the floor on the joists is ventilated, which is very important for the safety of the floor covering.
- It is very easy to place hidden communications – pipes or electrical wiring – between the joists. If necessary, gaining access to them to prevent or eliminate an accident is much easier.
- The presence of communications will in no way hinder the effective insulation of the floor - the niches between the joists “ask themselves” to lay thermal insulation material in them.
- With the help of logs, it is not at all difficult to level floors to an ideal horizontal level, even with very significant level differences. In this case (unlike concrete floors), material consumption practically does not increase.
- In addition to its insulating qualities, flooring on logs is much more efficient. sound absorption.
- The logs very evenly distribute and transmit static and dynamic loads to the base. The apparent simplicity of the design does not in any way reduce the strength qualities of the created floor.
- It is easier to repair a floor on logs - after dismantling the covering, it is enough to simply replace the damaged parts if necessary.
- The design with logs, by and large, can be used for almost any type of floor covering - it can be not only wood, but also any rolled material or, subject to the appropriate technologies, even ceramic tiles.
- Floors on joists were often reproached for the fact that they do not “join” well with water or resistive heating systems. However, technologies have now been developed that make it possible to organize any of the underfloor heating systems on such a surface - resistive, infrared or from a water heating circuit.
How to create mini-storage facilities in an apartment?
If the wooden floor is high above the base, for example on a balcony, this space can also be usefully used for household purposes.
Read about this in the article on how to do it.
Lag material, cross-section, pitch and laying direction
As already mentioned, the optimal lumber for making logs is timber, cut on special equipment with precise dimensions - width and height. Usually, not too expensive wood is used for these purposes - pine, spruce, fir. Larch shows very good performance and durability, but parts made from it will cost much more.
For lags it is not at all necessary to choose wood of the highest or first grade - the second will be sufficient. Third-rate timber, with a large number of knots, should be treated with a great deal of caution: after all, logs are load-bearing parts, and even if not in appearance, their strength qualities should be at their best. Cracks, rotten, and blue areas are not allowed - such logs will not last long.
Particular attention to the geometric correctness of the workpieces - deformed, twisted, curved beams will be extremely difficult to align at the same level.
The best option is if the lumber has already been dried on specialized lines, and its residual moisture content does not exceed 12%. True, such material and at home will need to create appropriate storage conditions before installation. Timbers with a moisture content of more than 15 ÷ 18% should not be installed - they may warp during final drying, which often leads to general deformation of the structure, the appearance of unstable areas on the floor, creaks, etc.
Usually for lag the timber is selected from the proportion that the height of the part is equal to one and a half to two times its thickness.
h = 1.5÷2 × a
But still, “where to start dancing”? What specific section of timber will be required in this or that situation? There are several criteria to evaluate here.
- If you plan to install a plank floor covering on the joists, you should most likely start by planning the location of the beams. The fact is that according to all the rules, a wooden floor is laid so that the seams between the boards are parallel to the direction of natural light in the room. Thus, the location of the logs in adjacent rooms may vary:
The diagram shows:
1 - walls of the building.
2 – entrance doors to the premises.
3 – windows and direction of natural light flow (wide pink arrows)
4 – lags. As you can see, their direction may vary.
5 – finished floorboards, always laid perpendicular to the joists.
If it is planned to lay sheet material along the logs as a base for the subsequent finishing coating, then the orientation of the location of the logs will not be of key importance.
- The next question is to decide how many joists are needed for each room. In other words, it is necessary to decide on the pitch of their installation (the distance between two adjacent parallel logs).
This parameter directly depends on the thickness of the board that will be used to install the final floor covering. There are certain standards that are shown in the table below:
Knowing what material will be used for the floor, based on the installation diagram drawn up, it will not be difficult to calculate the number of required joists and the exact distance between them. The step, of course, most likely will not be expressed as a round number, but it will only be possible to round it down. If necessary, it is permissible to lay the logs near the walls in smaller increments - the strength of the structure will only benefit from this.
- Now you can decide on the cross-section of the beam. The main criterion for evaluation when installing a floor in a private house, without a concrete base, is the distance between the support points, that is, the length of the joist span.
As you can see, the cross-section of the beam is directly proportional to the span length, and sometimes reaches very significant values. If the room is large, very powerful beams may be required, which will make the structure heavier and significantly increase the cost of lumber.
Logs with intermediate supports - posts
Therefore, for large spans, it is often practiced to install additional supports, for example, brick columns. This measure allows you to significantly reduce the required lag cross-section:
The cross-sectional values given in the tables are minimal and may vary, but only upward. For example, it happens that you need to increase the height of the log itself. This happens when it is necessary to make high-quality thermal insulation of the floor, which means it is planned to lay a thick layer of insulation. The height of the log for a structure assembled according to the principle of a rough and finished floor (a diagram of such a floor is shown and described slightly below in the text), in this case, will be summed up from the thickness of the skull block, the roll (subfloor boards), insulating material and the ventilation gap. Well, the width of the log remains tabular.
For logs that are installed on a concrete base, directly on it or on racks (linings) with a pitch between them of about 500 mm, such sections are not required. Here, a beam with a thickness of 50 mm is sufficient, and the height is determined depending on the required height of the surface (there is a limitation - at least 40 mm). The main thing is to choose the right step, as mentioned above.
To finish the issue with the selection and preparation of material, one more important point should be mentioned. The fact is that wood, as an organic natural material, is subject to decomposition over time - it can begin to dry out, rot, and rot. In addition, the tree is a favorite breeding ground for a number of “representatives” of microflora (molds, fungi, bacteria), insects and even rodents. Thus, in order to ensure the durability of the floor structure, its parts should be subjected to special treatment.
There are many ready-made formulations for this. Many of them, for example, the very popular Pirilax among builders, combine a dual function. Besides giving wood has antiseptic qualities and treatment for existing biological lesions, they sharply increase its fire resistance, as they contain fire retardants.
Processing is carried out after preparing the composition in the desired consistency (most often, it is sold ready for use). Impregnation can be applied with a brush, aerosol spray, and small parts can simply be dipped into a container with a solution. The approximate minimum consumption for just carrying out is about 100 ml/m² surface area of the workpieces. It is recommended to carry out a double treatment - the first layer is allowed to absorb and dry (at positive air temperatures this will take about an hour), and then the treatment is repeated.
To give the wood pronounced fire-resistant qualities, the processing consumption is increased to approximately 180 ÷ 280 ml/m², and the required consumption is ensured by several layers of application. And an increase in consumption to 400 ml/m² (also layer by layer) makes the wood difficult to combust - fire resistance class G1, flame spread - RP 1 , smoke generation- D 2.
Before processing beams for logs, they must be cleaned of dirt and dust, lime, paint, etc. There is no point in processing undried wood - firstly, the composition itself will be extremely poorly absorbed, and secondly, it will disrupt the process of normal natural drying of the material. The maximum permissible humidity before processing is 25%, although even at this maximum level the quality of processing will not be the same.
Prices for various types of timber
Installation of logs on the ground floor of a private house “on the ground”
The term “on the ground” is found quite often, but it is necessary to understand that, of course, in the vast majority of cases the logs do not contact the ground surface in any way. They can be attached to the beam of the lower crown using connecting metal parts or a notch.
Another option is to lay the logs with their ends on a foundation strip or grillage. In this case, a layer of waterproofing must be laid. Typically, roofing felt is used for these purposes. If it is less than 3 mm thick, then it should be laid in two layers.
On each side of the log, it should be at least 100 mm on the horizontal plane of the grillage, tape or beam.
1 – foundation tape.
2 - wall of the building.
3 – a layer of waterproofing material – roofing material.
4 – beam of the lower trim.
5 – lags.
6 – the required gap between the ends of the joists and the walls is at least 20 mm.
7 – corners for fixing the logs to the strapping beam.
This option is entirely possible if the span of the logs is not too large. If the dimensions are significant, a beam of the appropriate cross-section will be required, but this may not provide a guarantee that over time the lag will not begin to bend slightly. Therefore, the best option will become installation of support posts.
They are located along the axes of lag placement. The distance from the wall of the first column is approximately 500 mm, and the rest are installed at equal intervals in increments of at least 1 meter (see table above).
The pillars also need a foundation. It can be individual for each support...
...or a common tape is poured under a whole row of supports.
1 – building foundation strip.
2 – shallow foundation for support.
The simplest option for installing joists is directly on the plane of the concrete base. This is possible if there are no noticeable differences in height, the finishing coating does not require raising the level, and there is no need for strong thermal insulation.
In this case, logs of strictly the same section are simply laid out along the intended marking lines. It is recommended to lay a fiberboard strip between them and the concrete surface, treated with the already mentioned antiseptic composition.
The floor plan with insulation is extremely similar to the one given above, and there is no point in describing it in detail. The only difference is that there are no slabs or subfloor boards.
1 – concrete floor base.
2 – lags.
3 – fiberboard gasket
Further numbering completely repeats the first scheme.
The easiest way to fasten joists to the floor is with the help of corners, which are attached to the wood with self-tapping screws, and to the screed with driven dowels or anchors.
You can also use dowels with a hairpin top for fastening. In this case, round grooves are milled into the joist bars, where the washer and nut will be hidden.
The logs are placed on the floor taking into account the calculated step so that the distance from the first beam to the wall parallel to it is about 30 ÷ 50 mm, and the end ends do not reach the walls by 20 mm.
The situation is somewhat more complicated if it is necessary to bring the lag level into one plane, especially If for one reason or another it is necessary to significantly raise the floor. Previously, almost the only available method to achieve the goal was wooden pads (made from pieces of boards, plywood, etc.)
Installing joists to the desired level using shims is a thing of the past.
It would seem that the method is extremely simple, but it’s impossible to call it convenient, especially if the level of elevation or elevation difference is large. It is very difficult to precisely adjust the required height of the support; this often requires additional individual adjustment of wooden fragments. Multilayer stands need to be glued or twisted, but this does not give the structure high rigidity. Large support area on uneven, lumpy floors leads to the instability of her position. In a word, achieving high accuracy and guaranteed stability of the log system with this approach is very problematic.
Therefore, modern craftsmen are increasingly resorting to so-called adjustable joist systems. With this approach, the logs are mounted on stands, which in one way or another allow you to adjust the level height on each of the supports. It can be the simplest U-shaped brackets with holes for fixing the beam at a selected height, or threaded systems, in which it is even easier to change the height - by rotating the nut or screw post.
The figure shows only two types of adjustable stands, although in reality there are many more. It is simply impossible to consider everything on the scale of one article, so the step-by-step installation process of only two will be shown - log systems with U-shaped brackets and with threaded stud posts.
Log system for insulated floors on U-shaped brackets
To install such a floor, galvanized steel brackets with a height of 167 mm are used. They are designed for installation of logs made of timber with a cross-section of 40 × 70 mm.
For example, the process of creating a heated floor on a balcony or loggia.
| Illustration | Brief description of the operation |
|---|---|
 | The supporting element of the structure is a U-shaped bracket. |
 | To fasten the logs to the crossbars, you will need metal corners. |
 | The first step, as always, is to clean the base surface. If there are cracks, they should be sealed with foam. It would be a good idea to cover the concrete base with a deep penetration primer - less dust and additional waterproofing. |
 | Marking is being carried out. The joists along the walls are marked so that a distance of approximately 50 mm is maintained (from the side edge of the joist to the wall). |
 | The lag lines are drawn according to the identified risks. |
 | The line for installing the middle log (in the center), as well as the installation locations for the jumpers, is immediately outlined. It is taken into account that if the plywood covering consists of two or more sheets, then the joints should fall exactly on the lintels. |
 | The installation locations of the brackets are outlined. The step between them on one joist is 500 mm. On the lintel, one bracket in the center is enough. |
 | Holes are drilled in the floor for dowels to install brackets. |
 | The brackets are attached to the surface of the concrete base. It is necessary to ensure that the installation is even, so that the U-shaped bracket is not rotated relative to the center line. |
 | The first row of brackets for the outer joist is installed. |
 | The floor is supposed to be insulated, and issues of thermal insulation will have to be dealt with in parallel with the installation of the logs, otherwise it will be problematic to do this later. Slots are cut in the mineral wool strip so that the bracket shelves fit into them. This results in a single insulating layer, and in this case the metal will not become a cold bridge. |
 | The log beam is inserted. From one edge it is adjusted to a given height and temporarily fixed with one self-tapping screw. |
 | Move to the opposite side of the log. The beam is set strictly horizontally and is also fixed with a self-tapping screw. |
 | When installing beams along walls, there is one catch - they cannot be secured with screws from the wall side. There is a way out - in each of the brackets, directly through the log installed in it, two 6.5 mm holes are drilled. M6 bolts are inserted and tightened with a nut from the wall side - this is easy to do with a wrench. |
 | This is what each of the brackets with joists along the wall will look like. |
 | A series of brackets and joists are mounted in the same way on the opposite side. The main thing is to control that the bars are strictly at the same horizontal level. |
 | A series of brackets for the central joist are attached. |
 | In this place it is easier to attach the timber - the walls do not interfere. After laying the same thermal insulation as before, it is leveled and firmly fixed on both sides with self-tapping screws. |
 | Three lag lines are exposed. They withstand vertical loads well, but when exposed to the side there is no stability. To eliminate this drawback, you need to connect them with jumpers. |
 | For a jumper, as already mentioned, one bracket is enough. After its installation, a layer of insulation is laid. |
 | a piece of timber cut to the required size is placed in place and fixed to the joists strictly level using corners and screws... |
 | and then attached to the bracket. |
 | The distance between the jumpers is about 600 mm, but taking into account future joints of plywood sheets. The frame assembly is completed. |
 | You can move on to final insulation. To begin with, the remaining “windows” are filled with mineral wool... |
 | ...and then, if necessary, you can lay a second continuous layer on top. |
 | A sheet of plywood is cut, the blanks are laid on the logs. In this case, it is necessary to immediately outline the lines along which the screws will be screwed in. |
 | Sheets of plywood are fastened with self-tapping screws, so that the heads “sink” slightly, 0.5 ÷ 1 mm into its surface. The pitch between fasteners is 150 ÷ 200 mm. |
 | The result was a very smooth and durable base for laying any type of floor finishing. In addition, if it is necessary to create a comfortable microclimate on the balcony in winter, then film heaters can be installed in front of the covering. |
Installing joists on threaded stud posts
Another method of accurately setting lags, which has gained great popularity. Schematically, in section, the principle of fastening is shown in the figure:
The main supporting element is the M8 threaded rod. Its standard length is 200 mm, of which 40 mm is occupied by an expansion anchor with a diameter of 10 mm.
The kit for each rack includes two reinforced M8 washers with an outer diameter of 24 mm and a metal thickness of 2 mm, and two self-locking M8 nuts with nylon rings. For logs, timber with a cross section of 50 × 70 mm is usually used.
The tools you will need are a hammer drill with a Ø10 mm concrete drill, an electric drill (a powerful screwdriver), a 10.5 mm regular wood drill, a 25 mm drill bit for wood, and a cutter for making round grooves Ø 26 mm will be useful. To tighten the nuts, you can use a regular open-end and socket wrench size 13, but it will be more convenient and faster to work if you can find a tubular socket wrench of the same size that can be clamped into the screwdriver chuck. To align the horizontal, you will need a level - ideally a laser level, but you can get by with a regular one.
We will not dwell on the issues of marking and surface preparation - they have already been discussed earlier, and in this case the procedure is almost the same.
| Illustration | Brief description of the operation performed |
|---|---|
 | The prepared logs are folded in a “package” and aligned along the edges. Marks are made of the points at which the racks will be installed. In this case, the rule is observed - the extreme marks from the edge of the log should be approximately 50 ÷ 70 mm, and the approximate step between the supports should be 550 ÷ 600 mm. A 25 mm feather drill is inserted into the drill. They cut out recesses of approximately 15 mm. |
 | To maintain accuracy in sampling depth, either make a bright mark on the drill, or install a depth limiter on the drill. Such holes are milled in all joists. |
 | Next, the drill in the drill chuck is changed to a regular one, Ø 10.5 mm. The beams are drilled through exactly at the centers of the selected recesses. |
 | In order for the washer to fit tightly with its entire surface to the wood during assembly, the recesses are machined with a round cutter Ø26 mm. The result is smooth cylindrical grooves 15 mm deep with a through hole exactly in the center. |
 | Next, the logs must be laid out exactly along the marking lines. |
 | The log is pressed tightly against the floor surface, and through the previously made holes, holes are marked or immediately drilled in the concrete screed using a hammer drill. You must work carefully so as not to accidentally turn the wood around with the drill. |
 | To prevent the joist from moving out of place, after drilling each hole, it can be temporarily fixed with metal pins - for example, long thick nails. |
 | When the holes in the floor along the entire length of the logs are marked, the pins are removed and the beam is moved to the side. Concrete debris generated during drilling is shaken out of it. If necessary, the holes in the floor are deepened with a hammer drill (about 60 mm), and then the anchor parts of the stud posts are inserted into them. |
 | The anchor nut is tightened, causing the stud to “stand dead” in a vertical position. |
 | After all the studs in a row are installed and secured with anchors, one nut is screwed onto them so that they are located approximately 50 mm below the level of the future coating. Then one reinforced washer is put on top of the nut. |
 | After similar manipulations have been done with all the studs in the row, you can put a joist block on them. The holes in the joists must line up exactly with the posts. |
 | The same is done with all other lags. |
 | Then a washer is placed on the part of the studs protruding above the joists, and a nut is screwed on top. There is no need to tighten it yet. |
 | The most crucial moment is setting the logs to a single horizontal level. The height can be adjusted by twisting the bottom nut in one direction or another. Each rack is worked individually, using a laser or regular construction level. When adjusting, you must ensure that the lag is pressed tightly against the bottom washer. |
 | Once the level on the stand is guaranteed to be accurately set, you can tighten the top nut tightly, thereby securely fixing the beam. |
 | Both during the work of setting the logs and upon its completion, careful level control is carried out, both longitudinally and transversely... |
 | ... and diagonally. |
 | When all the posts are fixed, it is necessary to cut off the protruding excess parts of the studs with a grinder. You must work very carefully so as not to damage the wooden parts. |
 | Such supports, despite their apparent flimsiness, have excellent stability. Each of them, when properly installed, can withstand loads of up to 700 kg. For the rigidity of such a structure, transverse jumpers are not even required. You can immediately proceed to the installation of the plywood covering. |
To complete the overall picture, we can briefly mention one more type of threaded posts for joists.
They are hollow polymer cylinders with threads on the outside. In the lower part of the rack there is a hole for fastening it to the floor with a dowel, and in the upper part there is a hexagon for rotating it with a special key.
Holes of the required diameter are drilled in the lag bars, threads are first rolled into them, and then the posts are screwed into them.
After installing the logs and fixing the racks to the floor with dowels, rotate to achieve the desired level. Then the excess part of the plastic stand is simply cut off with a chisel or knocked down with a chisel.
At one time, very wide advertising was made for such racks, but, however, the network was immediately filled with not the most enthusiastic reviews about them. The craftsmen complained about the fragility of the screw cylinders, the difficulty of screwing them into wood, the ill-conceived system of fastening to the floor surface, etc.
However, the author of this publication has neither installed such a system nor observed it during operation. Therefore, it is wiser to refrain from subjective assessments, and it is better to post a video about such racks for joists for your reference.
Video: installation of an adjustable joist system
– on the pages of our portal. Technology also contains many subtleties.
There are many types and configurations of roofs: each house has a roof that is unique in size and some design features. The most popular is the gable roof: it consists of two planes connected to each other at an angle and resting on walls, the height of which can be either the same or different. The roof slope angles must be at least 9... 10 degrees, the length of the overhangs must be at least 400 mm. The upper part of the slopes ends with a ridge, and on both sides there are pediments that turn into a wall. A living space can be equipped under the roof: such roofs are called mansard.
Installing a gable roof on a house with your own hands is quite simple, but there is a certain procedure that must be followed.
Advantages of gable roofs
The gable structure is popular due to its simplicity, which allows you to build it yourself without resorting to the services of specialists. Its construction does not require the use of expensive materials. Due to the angle of inclination, atmospheric precipitation is effectively removed. It is possible to install original structures with convex and concave surfaces, which allows you to make the roof unique against the background of neighboring houses.
Basic information about a gable roof
A gable roof is designed in such a way that it can withstand not only its own weight, but also the weight of roofing materials, snow, and gusts of wind.
Installation of this type of roof can be divided into several stages. First, the installation of load-bearing beams is carried out, then the sheathing is installed, after which they begin laying the roofing material. The main materials for this are beams made of wood and nails. Rafters are a frame of beams fixed on top of the box walls of a house. In turn, logs, sheathing and roofing material are attached to the frame.
For a trussed gable roof, only high-quality materials should be selected, since the reliability of the roof and its appearance depend on this. The rafters must be of rectangular cross-section, made of even beams, without cracks, signs of rotting or insect damage. Pine fully meets these requirements: it is quite durable and resistant to atmospheric influences.
Recently, wooden beams for rafters have been replaced with metal profiles, which can increase the service life of the roof.
To build a gable roof, you need an edged board with a section of 150×50 mm and timber 150×150 mm. Work begins after the walls are erected. First, a beam - Mauerlat - is laid on top of the walls closer to the edge in the longitudinal direction, under which waterproofing material is placed. Then an edged board is installed on the translations along the building, which will later serve as the basis for the racks. The edged board is attached to the ceiling with nails, after which the racks are installed and their upper part is tied.
The next stage is the installation of the rafter system. First, pediments are installed, which are a continuation of the walls. They form 
triangles, the vertices of which will be the beginning and end of the ridge of the gable roof. Then the remaining rafters are installed so that they are located in the same plane. Their edges extend outward to protect the building from rain and wind. The middles of the rafters are connected by crossbars, which are supported by purlins and racks resting on the beam. The purlins and racks are reinforced with struts. Such reinforcement of the rafter system is necessary to provide strength to the structure, and in the case of using the attic space as a living space, to ensure safety.
The design of a gable roof can be different: the slope angles of the slopes can be unequal and equivalent, and the slopes can be of different lengths. To save energy, insulation is installed between the rafters, which is most often used mineral wool. A vapor-permeable film is laid on top of the rafters, and a vapor barrier film underneath: this is necessary so that the insulation does not accumulate moisture, which can deteriorate its basic qualities. From the attic side, logs are tacked to the rafters for attaching the finishing material. After completing the installation of the rafter system, the outer sheathing is installed, to which the roofing material is attached.
Roofing pie device
When installing a roofing pie, you must follow six basic rules.
After installing the rafters, the sheathing is installed: the distance between the elements depends on the type of roofing material used. Previously, slate was mainly used to create a roof. However, due to a number of shortcomings inherent in this material (including a short service life), other, more modern and advanced ones are increasingly being used.
The simplest and cheapest material is metal tiles: thanks to the outer protective layer, it is not afraid of corrosion, is resistant to mechanical and chemical influences, and does not become overgrown with fungi, moss and mold. However, there are a number of disadvantages: metal conducts heat and cold well, and during rain and hail it makes a lot of noise. In this regard, other roofing materials have found application.
Natural ceramic and cement-sand tiles are very effective, as well as corrugated bitumen sheets, soft tiles, slate and seam (copper and aluminum) roofing materials. They have good sound insulation qualities, do not require maintenance and have a long service life. But some features of these materials introduce additional conditions necessary for the construction of the rafter system. For example, ceramic tiles have significant weight and require a stronger rafter structure for their installation.
Attaching the joists for laying tiles requires a constant step, depending on the size of the tiles.
To protect against moisture and wind, a special element is placed on top of the ridge. A system of gutters is installed under the overhangs to remove atmospheric moisture. In the case of the construction of large area slopes, snow retainers are installed on the roof to prevent avalanches of snow, which can cause the collapse of the drainage system. The exit points of ventilation and chimney pipes are additionally insulated from moisture.
A properly constructed gable roof will last for several decades.
Before installing the rafter system, the question arises at what step to install the floor beams. Correctly calculating the distance between the rafters means preventing subsequent deformation or even destruction of the roof frame. After reading the article to the end, readers will learn what the distance between the rafters should be for different types of roofing and how to make the calculation correctly.
Even at the design stage of a wooden house, all load calculations must be made. This also applies to the rafter system. This is especially important in wooden house construction, since the top link is often used instead of a Mauerlat. It is difficult to correct errors in such a design later. There is a technique for correctly calculating the distance between beams.
The span of the roof frame for the construction of a house made of timber usually exceeds 1 m, and the smallest permissible value is 60 cm, such indicators are indicated in GOSTs (see figure). You can correctly calculate the length of the rafters and their pitch using the following option:
Using a tape measure, the length of the roof slope is measured, the result is divided by the pitch size of the roof frame. For example, if the distance between the rafters is 1 m, then you need to divide by 1, if 70 cm, then by 0.7. The resulting figure is added to 1 and rounded to the nearest higher number. This way you can determine the number of beams for one roof slope.
You need to divide the length of the future slope by the result obtained. The result will be the distance between each rafter.
For example, consider a roof whose slope is 25.5 m and in increments of 0.6 m. You need to calculate the following indicators: 25.5:0.6=42.5, to 42.5+1=43.5. We round this figure to the nearest larger integer, we get 44. This is the number of rafter beams per 1 slope of the future roof.
Now we calculate the span between the rafters: 25.5:44 = 0.58 m. It turns out that you need to install the legs of the frame after 58 cm. This way you can easily calculate the pitch of any roof frame, single or complex, without taking into account the roof. But professionals recommend their calculations for a certain type of roof.
Rafter pitch depending on material
Since each forging material has its own characteristics and features. Among the most common are:
- Profiled sheeting. It has different thicknesses and tropezoidal curve shapes. Costs from 120 rubles.
- Ceramic tiles. Expensive material from 670 rubles. Has 12 color options.
- Metal tiles. This is a cheaper material, unlike ceramic, and costs from 320 rubles.
- Ondulin. A soft roof insulates the house from rain, hail, etc. Costs from 340 rubles.
- Slate. The most economical option from 90 rubles.
We will consider the step size for the most common types of coverage below.
Spacing of rafter beams under corrugated sheets
The distance between the roof beams depends on the size of the sheet that the corrugated sheet has. The pitch of the roof frame beams under the corrugated sheeting is standardly taken to be no less than 60 cm and no more than 90 cm.
If this distance is greater, then boards with a larger cross-section are attached between the rafter beams. The cross-section of the rafter legs under the corrugated sheet is selected 50x100 or 150 mm.
The most important thing to consider when planning to attach corrugated sheeting is the sheathing. It is made from boards with a cross-section of 30x100mm; it must be mounted with a span of 50 cm. It depends on the brand and thickness of the corrugated sheeting and the slope of the roof.
So, a 15º roof, grade C 10 corrugated sheeting is mounted on a continuous sheathing, C 21 corrugated sheeting is mounted on the sheathing with a span of 30 cm. The largest corrugated board C 44 is mounted on the sheathing in increments of 50 cm to 1 m. In this case, before attaching the sheathing, you need to consider the free space passage of a chimney, ventilation hood, etc.
Spacing of rafter beams for ceramic tiles
The specifics of installing a rafter system for laying ceramic tiles are related to the weight of this roof. Ceramic tiles are made from clay, and this roofing weighs 9-10 times more than metal tiles. The calculation of the load on the rafter system for ceramic tiles is 40-60 kg/m2.
Beams for the roof rafter system for ceramic tiles are made only from dried material. The cross section is suitable 50x150 or 60x180 mm. The standard distance between the rafters for a tile roof is 80-120 cm. The span depends on the slope of the roof. At an angle of 15º, the span between the rafters is 80 cm, at 750 every 1 m 30 cm.
When calculating the step, you need to take into account the length of the beam. Taking the maximum length, the distance between the rafters is minimal. And, on the contrary, with a minimum length of rafters, the step is maximum.
When laying ceramic tiles, it is important to consider that you will need to walk on the roof. The maximum safe step of the rafter legs for such movement is 80 cm.
It is important when laying ceramic tiles to calculate the span of the sheathing. This distance is directly related to the size of the roofing material. A standard sheet of tiles is 40 cm long. Laying occurs with an overlap of 50 to 90 mm. When calculating the sheathing pitch, the overlap size is subtracted from the length of the tiles. The result is a pitch of 305-345 mm.
For a pitched roof for the construction of a house made of profiled timber, it is not difficult to make calculations. If the roof has a complex, multi-pitched shape, then each distance between the rafters is calculated separately per sheathing step. By securing the cord on the opposite side of the roof slope, you can easily mark the rows.
Features of the roof frame for metal tiles
Metal tiles are used more often than ceramic or corrugated sheets. Externally, the roof resembles ceramic tiles, but unlike it, it is easier to install and lighter.
Metal tiles weigh from 35 kg/m2 of roofing. This makes it possible to lighten the rafter structure and use beams of a smaller cross-section. The step between the rafter legs of the roof frame increases and is equal to 60 to 90 cm. The beam is used with a section of 50x150 mm.
To create a ventilated space, holes with a diameter of 12-13 mm are drilled in the beams under the roof.
The design of the roof frame for metal tiles is not much different from corrugated sheets or ceramic tiles. But there is a small peculiarity: the support from above is attached to the ridge girder from above, and not from the side as in other cases. This will create a ventilated gap under the metal tiles, which will prevent the accumulation of condensation.
Features of rafter legs for ondulin
Ondulin is a soft roof used for the construction of a house made of laminated veneer lumber or other material. Ondulin is produced in the form of sheets; it looks like painted slate, but is lightweight. This material is excellent for wooden houses, both low and large.
Rafter beams under the ondulin are placed with a distance of at least 60 cm, maximum 90 cm. For the rafter system, softwood timber with a section of 50x150 or 50x200 mm is used. A smaller cross-section will not provide sufficient strength to the rafter purlins.
The sheathing on the rafters is made of material with a cross-section of 40x50 mm in increments of 60 cm. This is quite enough for fastening sheets of ondulin with an overlap of 30 cm. Ondulin is fastened with special nails, which are sold as a set.
Features of the slate rafter system
Slate is rarely used to cover the roofs of modern houses. But in dacha construction and household. This material is irreplaceable in buildings. It is low cost and easy to install.
Slate rafters
Slate rafter legs are used with a section of 50x100 or 50x150 mm. The fastening spacing between the rafters is no less than 60 cm and no more than 80 cm.
Slate lathing is made from 50x50 mm bars or 30x100 mm wide boards. The sheathing is laid in steps depending on the slope of the roof. For a steep pitched roof it is 45 cm. The consumption is 4 bars per 1 sheet of slate. For a flat pitched or gable roof 63-65 cm, the consumption is reduced to 4 bars per sheet.
The pitch of the rafter system under slate differs in the roof structure. For households It is not uncommon for buildings to have a shed roof installed.
Feature of the size between the rafter beams on a single-pitched and gable roof
Whether a safety margin is needed during installation depends on the shape of the roof. And the distance between the rafter beams directly depends on this.
Single-pitch rafter system
A pitched roof is more durable and easier to assemble. The thickness of the rafters is selected depending on the type of wood, its strength and the specifics of a particular structure. The step between them can be 60-140 cm. The distance also takes into account whether the structure will be insulated. If yes, then the step should correspond to the width of the insulation.
The thickness of the rafter beams must be calculated depending on the roof slope. For a slight slope of 15-20º, you can use material with a cross section of 50x100 mm. For a steep slope of 45º, stronger ones with a section of 50x150 mm are needed.
Gable rafter system
If you do not calculate the pitch of the frame of a pitched or other type of roof correctly, the roof may move away, and the beams will sag and bend due to the weight of the structure. In this case, simple repairs are not enough; you will have to redo the entire structure. Therefore, it is so important to correctly calculate the distance between the legs of the rafters, depending on the roofing material used: corrugated sheets, ceramic or metal tiles, ondulin or slate, etc.
Rafters serve as the basis for the entire roofing structure, and their installation is one of the most important tasks when building a house. The frame of the future roof can be made and installed independently, observing the technological features of roofs of different configurations. We will present the basic rules for the development, calculation and selection of a rafter system, and also describe the step-by-step process of installing the “skeleton” of the roof.
Rafter system: rules for calculation and development
The rafter system is a load-bearing structure capable of resisting gusts of wind, taking on all external loads and evenly distributing them to the internal supports of the house.
When calculating the truss structure, the following factors are taken into account:
- Roof angle:
- 2.5-10% - flat roof;
- more than 10% - pitched roof.
- Roof loads:
- constant - the total weight of all elements of the “roofing pie”;
- temporary - wind pressure, the weight of snow, the weight of people carrying out repair work on the roof;
- force majeure, for example, seismic.
The amount of snow loads is calculated based on the climate characteristics of the region using the formula: S=Sg*m, Where Sg- weight of snow per 1 m2, m-calculation coefficient (depending on the slope of the roof). The determination of wind load is based on the following indicators: type of terrain, regional wind load standards, building height.
Coefficients, necessary standards and calculation formulas are contained in engineering and construction reference books
When developing a rafter system, it is necessary to calculate the parameters of all components of the structure.
Elements of the truss structure
The rafter system includes many components that perform a specific function:
Materials for making rafters
Rafters are most often made from coniferous trees (spruce, larch or pine). For roofing, well-dried wood with a humidity level of up to 25% is used.
A wooden structure has one significant drawback - over time, the rafters can become deformed, so metal elements are added to the supporting system.
On the one hand, metal adds rigidity to the rafter structure, but on the other hand, it reduces the service life of wooden parts. Condensation settles on metal platforms and supports, which leads to rotting and damage to the wood.
Advice. When installing a rafter system made of metal and wood, care must be taken to ensure that the materials do not come into contact with each other. You can use moisture-proofing agents or apply film insulation
In industrial construction, metal rafters made of rolled steel (I-beams, T-beams, angles, channels, etc.) are used. This design is more compact than wood, but retains heat less well and therefore requires additional thermal insulation.
Choosing a rafter system: hanging and suspended structures
There are two types of rafter structures: hanging (spacer) and layered. The choice of system is determined by the type of roof, floor material and natural conditions of the region.
Hanging rafters rest solely on the external walls of the house, intermediate supports are not used. Hanging type rafter legs perform compression and bending work. The design creates a horizontal bursting force that is transmitted to the walls. Using wooden and metal ties you can reduce this load. The ties are mounted at the base of the rafters.
A hanging rafter system is often used to create an attic or in situations where roof spans are 8-12 m and additional supports are not provided.
Layered rafters are installed in houses with an intermediate columnar support or an additional load-bearing wall. The lower edges of the rafters are fixed on the external walls, and their middle parts are fixed on the internal pier or load-bearing pillar.
Installation of a single roofing system over several spans must include spacer and layered roof trusses. In places with intermediate supports, layered rafters are installed, and where there are none, hanging rafters are installed.
Features of arranging rafters on different roofs
Gable roof
A gable roof, according to building codes, has an inclination angle of up to 90°. The choice of slope is largely determined by the weather conditions of the area. In areas where heavy rainfall prevails, it is better to install steep slopes, and in areas where strong winds prevail, flat roofs are installed in order to minimize the pressure on the structure.
A common version of a gable roof is a design with a slope angle of 35-45°. Experts call such parameters the “golden mean” of consumption of building materials and load distribution along the perimeter of the building. However, in this case, the attic space will be cold and it will not be possible to arrange a living room here.
For a gable roof, a layered and hanging rafter system is used.
Hip roof
All roof slopes have the same area and the same angle of inclination. There is no ridge girder here, and the rafters are connected at one point, so the installation of such a structure is quite complicated.
It is advisable to install a hip roof if two conditions are met:
- the base of the building is square in shape;
- in the center of the structure there is a load-bearing support or wall on which it will be possible to fix a rack that supports the junction of the rafter legs.
It is possible to create a hip roof without a stand, but the structure must be strengthened with additional modules - tie-down stands.
Hip roof
The traditional design of a hip roof involves the presence of slanted rafters (diagonal) directed towards the corners of the building. The slope angle of such a roof does not exceed 40°. Diagonal runs are usually made with reinforcement, since they account for a significant part of the load. Such elements are made from double boards and durable timber.
The joining points of the elements must be supported by a stand, which increases the reliability of the structure. The support is located at a distance of ¼ of the length of the large rafters from the ridge. Shortened rafters are installed in place of the gable roof gables.
The rafter structure of a hipped roof can include very long diagonal elements (more than 7 m). In this case, a vertical post must be mounted under the rafters, which will rest on the floor beam. You can use a truss as a support - the beam is located in the corner of the roof and fixed to adjacent walls. The truss truss is reinforced with struts.
broken roof
Sloping roofs are usually created to accommodate a larger attic. The installation of rafters with this roofing option can be divided into three stages:
- Installation of a U-shaped structure - supports for purlins that hold the rafter legs. The base of the structure is floor beams.
- At least 3 purlins are installed: two elements run through the corners of the U-shaped frame, and one (ridge purlin) is mounted in the center of the attic floor.
- Installation of rafter legs.
Gable roof: do-it-yourself rafter installation
Calculation of inclination angle and loads
Of course, you can calculate a gable roof yourself, but it’s still better to entrust it to professionals in order to eliminate errors and be confident in the reliability of the structure.
When choosing the angle of inclination, it is necessary to take into account that:
- an angle of 5-15° is not suitable for all roofing materials, so first choose the type of coating, and then calculate the rafter system;
- at an angle of inclination over 45°, material costs for the purchase of components of the “roofing cake” increase.
Load limits from snow exposure range from 80 to 320 kg/m2. The design coefficient for roofs with a slope angle of less than 25° is 1, for roofs with a slope from 25° to 60° - 0.7. This means that if there are 140 kg of snow cover per 1 m2, then the load on a roof with a slope at an angle of 40° will be: 140 * 0.7 = 98 kg/m2.
To calculate the wind load, the aerodynamic influence coefficient and wind pressure fluctuations are taken. The value of the constant load is determined by summing the weight of all components of the “roofing cake” per m2 (on average 40-50 kg/m2).
Based on the results obtained, we find out the total load on the roof and determine the number of rafter legs, their size and cross-section.
Installation of Mauerlat and rafters
Do-it-yourself installation of rafters begins with the installation of a mauerlat, which is fixed with anchor bolts to the longitudinal walls.
Further construction of the structure is carried out in the following sequence:
Installation of rafters: video
Methods for connecting rafter structure elements: video
The rafter system is the frame of the roof of the house, which carries and evenly distributes the weight of the roofing pie, sometimes reaching up to 500 kg/m2. The reliability of this unique frame depends on three factors: the accuracy of the calculation, on the basis of which the number and cross-section of the supporting elements are selected, the material from which it is made, as well as the correctness of the fastening technology. Knowing how to properly fasten rafters, you can significantly increase the load-bearing capacity of the frame, making it stronger and more reliable. Installation errors, on the contrary, lead to significant losses in strength and deformation of the roof. In this article we will talk about the main types and methods of fastenings with which you can qualitatively install rafters with your own hands.
The rafter frame of the roof of a house is a system of interconnected supporting elements made of wood or metal that give the structure its shape, slope, and also evenly distribute its weight between the load-bearing walls. Its main component is the rafter legs, which are beams installed at an angle, which are connected in pairs along the slope, forming a ridge at the top point of their connection. There are two main types of rafters:
- Layered. Layered rafters are called supporting elements that have two points of support in the roof structure - on the ridge girder and the mauerlat. A rafter system of this type is used in structures that have one or more load-bearing walls inside on which rafters can be “leaned.” This fastening of the rafters allows you to relieve them through the use of additional vertical supports.
- Hanging. Hanging elements are those that have only one support point, located where the rafters are attached to the wall or mauerlat. A hanging type rafter system experiences load not only in bending, but also in expansion, so it is strengthened by horizontal compensating elements (crossbars, tie rods, tie rods).
Note! In most of the most popular rafter systems, the rafters are attached to the Mauerlat. Mauerlat is a massive beam or beam with a cross-section of 150x150 mm or 200x200 mm, laid along the load-bearing walls of the structure, on which the rafter legs will subsequently rest. It softens the pressure on the walls of the house and also evenly distributes the weight of the roofing pie. You can attach the Mauerlat to the upper chord of the walls using anchor bolts or embedded metal studs.
Main connecting nodes
The rafter frame is called a system because all its elements are closely interconnected and fixed, as a result of which the roof structure acquires a stable shape, rigidity and high load-bearing capacity. Each connecting node between its parts is a vulnerable point that can easily deform under load, so all fastenings must be carried out strictly according to technology. Experienced craftsmen identify the types of connections in the roof structure:
- Attaching the rafters to the ridge beam. This connecting unit is typical only for layered rafter systems, in which the upper part of the rafter leg rests on a ridge girder mounted on vertical posts. The rafters can be attached to it using metal plates, nails or sliding slide fasteners.
- Fastening the rafters to the mauerlat. The most important fastening point of the rafter frame is considered to be the junction of the mauerlat beam with the rafter legs. You can fix the rafters on it using nails, metal corners or wooden blocks.
- Connecting the rafters to each other. To lengthen the rafter legs, if the length of the slope exceeds the standard length of lumber, they are assembled from several elements connected to each other using nails, glue or metal plates.
- Connection of rafter legs with auxiliary supporting elements. In truss frame construction, rafters can be connected to tie rods, transoms, or struts to increase rigidity, strength, and load-bearing capacity.
Please note that any cuts made to attach the rafters to the beams, mauerlat or other structural elements of the frame lead to a decrease in their strength, so experienced craftsmen recommend connecting them together using corners and overlays.
Fixation methods
When deciding how to attach rafters to a mauerlat or ridge girder, you need to choose the right fastening hardware. The modern construction market has a huge range of fasteners of various designs and sizes. The main criteria for choosing fasteners are the material used to make the rafters, their cross-section, as well as the type of load to which they are subjected. There are the following methods of fastening rafters:
Experienced craftsmen believe that the most reliable way to fix rafters is to use metal corners that firmly connect the wooden elements to each other, rigidly fixing the angle between them. The corner that covers the joint between the rafter leg and the ridge beam or mauerlat serves as a kind of spacer between them.
Types of fastenings
Wood is a natural material that, in the process of equalizing humidity and drying, causes significant shrinkage, which is why the linear dimensions of the structure change. That is why experienced craftsmen recommend erecting a roof for timber and log houses a year after construction, when the shrinkage process passes from the active to the passive phase. If you fix the wooden frame elements rigidly, then after drying the roof of the house may become deformed. Therefore, the following types of fastenings are used to connect rafters:
Interestingly, there are several options for combinations of movable and fixed connecting nodes. The most common are rafter systems with one rigid and two sliding fasteners, which provide sufficient mobility with high strength and rigidity of the structure.
Types of fasteners
There is ongoing debate among experienced roofers as to what is the most effective way to attach rafters to floor beams and mauerlat. However, in most cases the problem is that in these conditions it is more practical to use nails or self-tapping screws. Both of these fasteners have their own advantages and disadvantages:
- Nails are good because all you need to hammer them in is a hammer, which is available in every household. However, some craftsmen complain that hammering them in by hand takes too long. It is worth recalling that special jagged nails are used to fix the rafters, which securely adhere to the wood.
- To assemble the rafter frame, galvanized self-tapping screws are used, which are not afraid of corrosion. Due to the thread, they are firmly screwed into the thickness of the wood, securely fixing the elements together. Screwing them in quickly and conveniently with a portable screwdriver. The disadvantage of this type of fastener is that during dismantling, removing screws from wood is long and tedious.
Most experienced roofers agree that to fix rafter legs it is better to use galvanized rough nails, the length of which is 5-3 mm greater than the thickness of the lumber. Properly selected fasteners are the key to high-quality and long-term fixation of the roof frame, which will not be afraid of either mechanical stress or wind load.
Video instruction
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