The main mistakes when installing floors and roofs. Repair of an old slab roof in a workshop. Hip roof supported by floor slabs.

Floors different types have their own installation technology, which must be strictly followed.

The general rule is that the ceiling is aligned with the ceiling of the lower floor. Since it is this that gives spatial rigidity to the structure of the house, all its parts are rigidly connected to each other and to the walls (welding, concreting, anchors).

It is not allowed to punch holes in the floor slabs that are not provided for by the design (so as not to damage the ribs and reinforcement in the slab), shorten (cut) the floor slabs, or overload them during installation in excess of the standard load. The most common mistake is reducing the area of support of the ceiling on the wall(compared to design).

Consequences. Deflection and collapse of ceilings, cracks in walls and ceilings (for example , the permissible deflection for a round-hollow slab with a span of 6 m is 15 mm).

Elimination. If the deflection is greater than permissible, the load on the slab should be reduced or strengthened in a manner specified by a specialist.

How right. It is necessary to strictly follow the design and instructions for the technology of installation of floors. If, as a result of an error during the construction of the wall, the problem of insufficient support area has arisen, the specialist must develop a unit for this area that allows it to be increased.

Mistakes during roof construction

The attic wall is not reinforced

Consequences. The inclined rafters act on the attic wall in a horizontal direction, creating a thrust, which causes the wall to collapse.

Elimination. Convert the hanging rafter system to a layered one.

How to do it right . When constructing an attic wall, it is initially necessary to provide a layered rafter system (with a support point in the ridge area).

The vapor barrier film is not tightly installed

Consequences. There are pockets of steam penetration into the insulation, causing moisture to accumulate in the under-roof space.

Elimination. Disassemble the structure, inspect the rafters, replace damaged elements. The insulation needs to be dried or replaced.

How right. When installing a vapor barrier, the film is placed on the walls around the perimeter of the attic. Special wide mounting tape Carefully seal joints and junctions with structures. The use of nails is prohibited.

There is no ventilation layer in the roofing “pie”

Consequences. Moisture can accumulate in the insulation, causing it to lose its properties.

Elimination. Disassemble the structure, inspect the rafters, eliminate damage, and re-install the roofing “pie”.

How right. The under-roof space must be ventilated through an air gap that is left between the insulation and the waterproofing film. Without a gap, only a superdiffusion membrane can be laid on the insulation.

When installing bitumen and metal roofs(seam, metal tile), under which condensation forms, ventilation gap also arranged directly under roofing covering. Openings are left under the roof overhang for air flow, and devices for air outflow are installed in the ridge area.

The type of coating has been changed to a heavier one

Consequences. The rafters die, as a result of which the roof becomes deformed, begins to leak and may collapse.

Elimination. Gain rafter system.

How right. When changing the type of roof, it is necessary to order from a design engineer a recalculation of the rafter system for a more massive covering.

Semyonovich, I couldn’t find an answer to this question on the internet. Coven. in a workshop made of reinforced concrete, total area 80 by 24 meters, slope of approximately 5 degrees, filled with bitumen. It is proposed to tie the rafters directly onto it with wire to the floor slabs. But I can’t imagine how. It is clear that you need to drill holes in the slabs, but how to insert the wire into one hole and pull it out again into the next one to tie the rafter? It’s impossible to walk down there, there’s nothing to walk on. Maybe there is another real and simple way to attach the rafters, please advise. Insulation between the rafters is also expected.

Alexey, Vologda.

Hello, Alexey from Vologda!

A very non-standard question is how to secure wooden rafters to the workshop span. Therefore, the answer to it is not visible on the Internet.

More and more of these are simply re-coated with roofing felt (rubemast, glass insulation and the like) directly over its old layers, including the layer of poured bitumen. Sometimes these old layers of roofing are torn off. But this, of course, is difficult. New electrical installations are being fixed roofing material as before, without deleting it. But they are still a rarity for our great and vast country.

I admit that I have never blocked workshop spans using your method.

Smaller areas were also available in several other variations.

At the same time, we laid wooden beams (and boards), an analogue of your rafters, and attached them to reinforced concrete slabs not with wire, but in a slightly different way.

They took a steel corner with a shelf about 63 - 75 millimeters, cut it with a grinder into pieces 50 - 100 millimeters long. Holes were drilled in these scraps along both shelves. Holes for self-tapping screws /2 - 3 pieces/ were made in the vertical shelves (about 5 millimeters in diameter), and in the horizontal shelves one hole with a diameter of about 12 - 14 millimeters. (As an option - take steel sheet 1.5 millimeters thick, cut into strips, then bent into a corner and holes were drilled).

After this, the trimmings of the corner were applied with a vertical shelf to the surface wooden beam and attached it to it with self-tapping screws.

And the second horizontal shelf lay on the surface of the reinforced concrete slab.

Through a hole in the bottom flange of the corner, a hole was drilled in the slab or through hole(when it was opposite the cavity cell of the slab).

Then they took anchor bolts (you can use a wedge anchor), inserted them into the hole, and drove them in with a hammer. Then, using a drill with a head for the bolt, they screwed the anchors in until they stop. True, the number of anchors was decent, but they are not cheap.

We got a completely normal fastening. The following features were taken into account.

First, we calculated the approximate pitch of the reinforcement that was in reinforced concrete slabs Oh, the ceilings, so that you can’t get into them with a hammer drill and you can put an anchor in them.

Secondly, when looking from below, the view was not always presentable; in some places, potholes were visible on the surface of the slabs (where the hammer drill hit large crushed stone, component concrete, and it fell out.

Third, the rafters were not immediately attached to the slabs, but the longitudinal joists. And only then rafters were laid on them and secured with staples, nails, and screws. This results in fewer fastening points, which means less labor intensity.

All pieces of wood were impregnated with KSD, "Senezh". This is what the customer required in accordance with the regulations. Experienced customers always carry out author's control and often require the use of not colorless compositions, but with color. Then you can see whether there is coverage or not. You know, coven-makers are not always scrupulous in this matter.

I can't say anything about other methods. You can, of course, lay it out along the rafters, drill holes next to them with a hammer drill and, driving around overhead crane inside the workshop bay, insert the wire into these holes and twist it. But this is somewhat difficult. Yes, and there may not be a crane, but you can’t jump with a ladder.

But this is all speculation on a free topic.

Now what would I personally do if I were you?

In your case, floor slabs are most likely used. If memory serves, with spans like yours, their dimensions are about 9 meters by 1.5 (or 1.8) meters. The load-bearing reinforcement in such slabs is located around the perimeter. And throughout the area there is welded mesh with a large cell. Wire diameter is from 3 to 5 millimeters. The plate itself has stiffening ribs. And the thickness varies around 50 millimeters.

The slabs are supported on reinforced concrete arch-trusses. The joints of the slabs along the grooves are interlocking or simple.

Then it is most advisable not to use logs, as we did with conventional rectangular flat reinforced concrete floor slabs, but to use them for rafters edged board cross section 40/150 millimeters. Lay it flat on the surface. “40” is more suitable here than “50”; it bends better. Laying, respectively, from the edge to its center.

Then the sheathing boards can be taken in measured, six-meter lengths and placed lengthwise without any bends.

Press the rafter boards firmly to the surface. That is, secure one end of the board, then a couple of people from the team should stand on the other end of the board. It will curve and hug the slope of the roof. Then fasten the next anchor bolt. The fastener pitch is about 1.5 meters. Drill holes for anchor bolts directly into the boards at their centers. And then drilling into the slabs themselves.

The anchor should also be driven in with a hammer and screwed in with a drill with a head. It is most likely not advisable to use a screwdriver; its power may not be enough. To prevent the head of the anchor bolt from falling into the wood, you can play it safe and put a large diameter washer under it. The length of the anchors should be approximately equal to the total thickness of the board, bitumen layer, plus the thickness of the floor slab.

There should not be many different kinds of holes along the perimeter of the roof in order to exclude the so-called windage, when the upper wind enters a confined space and is capable of tearing the roof away from its base. Extreme events like this are rare, but they do happen.

Everything proposed does not quite fit into SNiPs; they would recommend placing the rafters on edge for greater rigidity, using a 50/150 board, adjusting its surface to the slope, and using an edged board, also 50 millimeters thick, as a sheathing. Or remove layers of old roofing felt, do concrete screed, or even completely tear off the old floor slabs and install new ones with a new layer soft roof. But your customers are unlikely to pay such costs.

I repeat once again that you may have simple reinforced concrete slabs, or maybe floor slabs, and accordingly, the mounting options may be different.

Focus on the circumstances. Try it, experiment.

As for the insulation, there won’t be any special problems. Isover, ursa, mineral wool, polystyrene foam, whatever your heart desires. If you observe all decency, then you need air gaps, various thermal films, in worst case glassine and all this on the counter-lattice. If the insulation is soft and 50 millimeters thick, then it’s okay, the “40” board will work just fine, you just need to press it down a little.

However, this is my vision. The decision is still up to you to make.

Features of hip roof design

If you look closely at the classic hip roof, it becomes clear that it was created primarily for two or three storey buildings, for conditions with big amount precipitation and variable direction of strong winds. It is not for nothing that such designs are also called Dutch or Danish. This is where the benefits of a hip roof are obvious. But the beauty of the design sometimes makes it necessary to make hips just for the sake of appearance the roof and facade of the house, and not any special properties.

If we compare the dimensions and material costs of a gable roof and a hip roof, we can draw the following conclusions:

Making two additional roof slopes instead of flat gables is beneficial due to lower costs for a wooden beam frame, but unprofitable in terms of consumption of roofing materials;
If you make the walls of a house from modern aerated concrete blocks or bricks from an arbolite mixture, this will reduce heating costs, but the costs of reinforcement will increase significantly load-bearing frame hip roof, almost 25-30%;
Making a roof hip design It is beneficial if the house is located in conditions of constant strong winds and heavy rainfall. In this case, heat loss on a gable roof is 5-10% higher than on a structure with hips;
With the same consumption of materials, making a simple hip roof is more expensive due to the need to pay for the services of more qualified builders and specialists;
A structure with hips, given the same quality of construction, is considered stronger and more durable in comparison with gable roof designs.

Important! Today, the hip roof has become almost a classic of the genre in the architecture of low-rise construction of cottages and country houses.

Make a hip roof and not make a mistake

A hip roof today can look very beautiful and original. Modern developments in hip roof designs make it possible to install it on almost any modern building, with or even without a foundation. If the building does not even have a strip foundation of normal depth, a hip roof can be made according to the simplest scheme - with a very small slope of the roof slope, a large offset hanging rafters and a wide roof overhang. Naturally, complete attic space and the overlap arrangement will be impossible due to the weak stability of the house frame. This approach will allow for minimal aerodynamic load from the wind, good protection walls and foundations from rain flows, and will reduce heat loss through the upper parts of the house. Great option for a small country house.

Basic assembly diagrams for a hip roof frame:

A structure supported only by walls, without the use of floors or ceiling beams;
The layered version of the frame installation allows you to increase the size hipped roof in height;
A roof supported on the house's floor beams is the most commonly used option for houses with light walls with insufficient rigidity of the building frame;
A hip roof supported on floor slabs is the most common option in modern construction two and three-story houses.

Hip roof supported by slabs

Unlike usual gable roofs, in which the angle of inclination of the flooring can be from 30 - 65 o, hip schemes have an optimal angle of 45 o. Almost all constructions and calculations are performed based on the specified angle of inclination of the main frame elements - diagonal rafters. This option provides maximum structural strength.

The use of layered schemes and supports on beam floors

Most often, such a roof rests with the lower part of the rafters on a mauerlat made of timber or thick boards, attached to the upper end of the brick or concrete walls of the future house. Together with the foundation, the walls form a rigid semi-closed system that can withstand vertical and horizontal loads from the rafters. Installation of a ceiling made of logs, timber or boards in such schemes is necessary to form the ceiling and attic floor. The ceiling itself in holding the roof or individual elements does not carry a hip structure.

In a layered design rafter supports there is also usually an option ceiling, made from wooden beams. At small sizes At home, the specific strength of the floor is enough to partially take on the load from the ridge girder and rafters. If the length of the beam increases to more than 5 m, the strength of such a floor is clearly not enough to hold the roof. Therefore, support columns or even part of the walls are built in the central part, on which the central part of the floor beam rests. The load from the ridge girder is transmitted through vertical support posts to one powerful central beam, called the beam. Sometimes the force from the weight of the structure is transmitted through the beam directly to the stone supports, without the participation of the ceiling itself.

Thanks to this load redistribution scheme, the rafters can be thinner and lighter, and the pressure on the walls of the house can be reduced by 30-40%.

Using joists to support rafters

Often, in the design of a house, the ability of the main walls to support the vertical load from the weight of the roof and frame is not always the decisive factor. A similar situation often arises in designs panel houses, in buildings with lightweight walls, or when using blocks with low rigidity, such as arbolite stone, as the main material for walls.

In these cases, even partial unloading and transfer of most of the pressure from the weight of the hip roof from the perimeter external walls to internal stone walls and the support does not solve the problem. The rigidity and strength of the main frame of the building is not enough to reliably hold even a hip roof, not to mention a gable roof. The problem of additional rigidity can be solved by making a special ceiling made of wooden beams at the base of the roof, with a cross-section of 20x20 cm or 20x15 cm. The beams are laid on top of the finished Mauerlat, extending beyond the walls by 60-70 cm, in increments of half a meter. The timber floor must be supported by one of the internal walls.

The ends of the beams protruding beyond the walls are used to fasten the lower parts rafter legs, and in the central part of the ceiling a frame is installed with supports supporting the ridge girder and the upper part of the rafters. The main part of the structure - diagonal rafters - are installed in the corners of the floor and connected at one point on the ridge girder.

Hip roofs with supports on floor slabs

Structures with hip triangles have long become a mandatory attribute of two or three-story brick and stone cottages built according to classical technology with laying of reinforced concrete slab ceilings. Due to the high strength of the boards and brick walls There is no problem of ensuring the required rigidity of the supporting surface under the frame.

To support the weight of the frame, the same scheme is used as in the layered version. A frame with vertical posts and struts, which absorbs the force from the ridge beam and rafters, rests on a bed mounted on concrete slab ceilings

Features of constructing a hip roof

The design can withstand any wind load, but subject to strict adherence to the geometry of the connection of the four main diagonal rafters.

Accuracy of connection and rafter geometry

All efforts may be in vain if violated optimal angles the inclination of the hip rafters to the ceiling and the angle between them. The best option A scheme is considered in which the corner hip rafters are connected to each other at an angle of 90 degrees.

The optimal angle between the hip beams is an important, but not sufficient condition for the strength of the hip roof frame. If you look at the roof frame in profile, both hip planes should be absolutely same size and the same angle of inclination. Otherwise, the structure will be overloaded on one side, and this is the first step towards deformation and destruction. If you look at the frame from above, you can see that with ideal assembly, the opposite corner hip rafters should be parallel.

Methods for connecting beams and rafters of a hip roof

Despite the efforts made to unload part of the structure, it is difficult to make the frame absolutely ideal in the location of the beams and power elements. Therefore, in all main load-bearing beams and rafters, metal overhead plates and wooden overhead elements are used when fastening and fixing to the walls.

Most often, beams and rafters are grabbed together “roughly” at the setup stage; the easiest way to do this is with self-tapping screws and clamps. After adjusting the dimensions of all connections, you need to check the position of the beams and rafters, then all the fasteners are finally connected, it is easier to do this with nails, hammering them in pairs at different angles.

The first to fix the bundles of diagonal hips on the ridge girder is to check the removal of the opposite beams from the calculated location. This is the most important and difficult stage of assembling the structure, and it is important to do this procedure slowly and very efficiently. The qualifications of the hip roof builder are evident precisely at this stage; all subsequent work is fully capable of being done to an ordinary carpenter who has a general understanding of the structure of diagonal rafters and hips.

The load on the diagonals of hip roofs exceeds the force on an ordinary rafter by more than one and a half times. Therefore, the configured and secured corner hips are first strengthened with struts and stops. Each of the supporting elements is adjusted individually and is also fastened with reinforced connections. At the next stage, it is important to correctly install the frames and ordinary rafters; upon completion, you need to tighten the fastening of the rafter legs on the mauerlat or floor beams.

Before laying the vapor barrier, it is imperative to treat it with preservative solutions. It is simpler and safer; you can use the most popular Tikkuril compositions based on an organic solvent.

Conclusion

Making a roof with hips is not so difficult if the team has a real specialist who can be entrusted with monitoring the implementation of the main, especially critical connection points of the power elements. It is possible to do this work yourself, without having practical experience in building hips, but the construction itself will last for several months, and the cost of damaged material will be exactly the cost of the services of a qualified specialist.