Construction of houses

Mansard roof rafter system: construction technology

In modern private construction, the roof truss system makes it possible to increase the living space and create an additional half-floor. This design is distinguished by a variety of design options, their reliability and versatility. It is convenient for installation of dormers and skylights and access to a small balcony on the roof. Such a constructive completion of the building makes it possible to organize additional living space instead of the usual attic. The attic level is formed thanks to a specific rafter system and a large angle of inclination.

Table of contents:

What type of attic space to choose?

For the first time, attics began to settle in Europe after the Second World War, when there was not enough full-fledged housing for everyone. However, in our time, the attic, as an elite housing under the roof, has become very fashionable. The construction of mansard roofs was taken up in the dacha sector, and in country cottages, and in already new houses, in order to add usable space.

Today, the installation of the roof truss system has become much easier and more affordable, thanks to the offer of the latest developments and the availability of building materials. High-quality insulation and new methods of sealing the attic roof have turned an ordinary attic into a cozy room. This made it possible to protect the living space under the cold roof from the cold and negative weather factors. And the rafter system of the attic roof allows you to vary the configuration, size and shape of the under-roof space. Attic construction options:

  • cold summer – country house;
  • insulated – for full-fledged year-round living.

Mansard roof rafter system – photo:

The side walls of the attic inside have different wall shapes:

  • symmetrical and asymmetrical;
  • single-level and two-level;
  • vertical (with additional pantries on the sides);
  • partially vertical (the bevel for the ridge starts from about the middle of the wall);
  • inclined;
  • beveled triangular (in the shape of the slopes of the attic roof);
  • broken lines (complex shape attic).

The total volume of the attic space, which is provided by a tetrahedral (hip) or gable roof, depends on the angle of the bevel. With competent cladding of the interior and thoughtful design, the room can be aesthetic and full-fledged for living, even with strongly sloping walls.

When the under-roof space must be designed for housing, it is important:

  • bring all communications down;
  • determine the layout and functionality of 1 or more compartments;
  • provide ventilation, heat and waterproofing;
  • take care of additional insulation for the winter;
  • bring all the amenities if it is an isolated room for one person.

Architect’s advice: The living space inside the attic is planned to be easy to move and comfortable for life support. Therefore, the dimensions of the room should be at least 3 m wide, and there should be enough space above the head to move freely with raised arms..

The preliminary calculation of the roof truss system is very important. All points should be thought out in advance, entering the preliminary attic project. Sometimes it is necessary to replace the roof, and the decision to complete the attic comes in the process of choosing a roof configuration..

Attention: The construction of the roof roof structure of the truss system should be carried out taking into account the fact that it will create an additional load on the foundation and walls, which is harmful for a not new house. And although this will not destroy the main structure, it can give additional shrinkage..

It is not too late to abandon the idea of ​​arranging an additional residential floor if the building is dilapidated and the soil is not suitable for multi-storey buildings. Only specialists of a construction organization or an architect can correctly calculate the total load, he will also prompt the optimal configuration (geometry) of the attic room so as not to spoil the appearance of the house. The angle of inclination of a new building is determined at the design stage. It depends on such factors:

  • climatic conditions of the region;
  • roofing materials;
  • functionality of the interior.

Mansard roof rafter system – drawings

An attic space cannot be planned without special windows. It is important to think over their location even at the design stage, that is, before installing the rafter system. In the end, not only the appearance of the house, but also the reliability of the entire structure will depend on the competent laying of window openings that affect the step between the supports. It is also necessary to consider the method of fastening the frame of the attic windows, and their height is dictated by the ease of maintenance inside the attic room..

Where to start the construction of the attic rafter system:

The rafter frame is the base or skeleton of the attic. And if you are interested in how to make a roof truss system, you should start by studying the existing experience, so as not to invent anything and not allow any annoying mistakes. If the rafter “cap” is installed and mounted correctly, then sheathe it from the outside and from the inside is no longer difficult.

The do-it-yourself roof rafter system is assembled in order:

  • mauerlat;
  • base from beams;
  • frame racks;
  • runs;
  • hanging rafters of the upper slopes.

Tip: When erecting an attic, all wood must be dry and seasoned, treated with a special antiseptic or antifungal aerosol. Logs and dry timber should have a moisture content of about 18-20%, no more.

Consider the next stage of work – a diagram of the roof truss system. Basis of construction:

  • main racks,
  • floor beam,
  • side rafter,
  • ridge rafter,
  • top harness,
  • fastening brackets.

How to make a mansard roof for a small summer cottage?

All work on the construction of the gable roof truss system can be done with a small team of henchmen.

If you want to build a cold summer attic over a small summer cottage, it is important to think about how you can get to the upper room:

  • on external attached steps;
  • from the inside, like an attic staircase.

Light boards, beams and small diameter logs are suitable for the prepared perimeter of the country house. However, the integrity and reliability of the lightweight construction of the attic room will depend on the reliability of the joints of the rafter system with the floor beams. You can use strapping, screws, nails, bolts, etc..

The racks are stacked in order with support on the beams of the base and floors, then the rafter legs of the first level of the slopes are attached to them. The main nodes of the attic rafter system are fastened either with construction staples or with hardened wire strapping. Sometimes an additional connection with reinforcement with staples or wire is required.

The upper beam of the attic floor is attached to these supports – this is a ridge post that “collects” the rafters under the upper slope. Next, the rafter legs are fixed for the upper level of the slopes, after which the rafter legs are connected with the main floor beams.

When the base is ready, all supports are fastened with straps and lathing, for additional reliability, so that the rafter system is strong and convenient for laying insulation, waterproofing and roofing material. The simplest construction of a country attic is covered with waterproofing and covered with slate. And don’t forget the rainfall drainage system.

An attic made of layered rafters is made in about the same way, but the tops are reinforced with a thicker bar – for sufficient structural strength. Such a system will functionally replace the support beam of the upper slopes. They will become the supporting frame of the attic roof and the basis for wall and ceiling cladding indoors – photo:

The lower level has options for fastening the support along the upper points of the rafters – on the side girder of the racks, on the gables, or only on the racks, that is, without mounting the side girders. And the lower points of the rafters of both lower slopes should rest on the floor beams, and preferably without a tie-in.

Under a roof made of heavy piece materials, it will be necessary to reduce the interval between the rafters, and also add the lathing of their cross beams. These schemes are often used for the construction of mansard roofs of complex configuration..

Useful Tips

It is important to build a roof attic, knowing some of the design features. Therefore, experts recommend that you learn a few lessons – how to properly make a roof truss system. We start with Mauerlat.

1. Mauerlat – that warp around the perimeter of the house, on which the entire rafter system is attached. Therefore, the reliability of the fastening of the lower beams to this perimeter will depend, in the literal sense, whether the roof will rip off due to unfavorable weather and climatic phenomena. A high-quality Mauerlat will not allow the roof of the attic to come off in a tornado or topple over during powerful hurricane winds. Reliable fastening of the truss structure to the perimeter of the building evenly distributes the load of the roof onto the walls and foundation of the house.

2. Boards and beams are better to choose strong, not knotty, with a thickness of 40mm. Under the Mauerlat, it is better to use dry processed wood, optimally – a bar with a section of 150x100mm. After preparing the perimeter of the walls for laying the rafters, the timber or board must be laid horizontally, adjusting the level along the entire perimeter of the walls.

3. On the crowns of walls or columns of a frame-type structure or brickwork, a layer of waterproofing recommended for the type of building materials must be laid. This is necessary so that the moisture content of the walls and the base of the rafter system does not transfer to them. Bitumen, roofing felt or roofing felt, other modern waterproofing materials are suitable for waterproofing..

4. The beam at the base is fastened to the walls with bolts or brackets; additionally, the fastening can be reinforced with a wire strapping. Mauerlat studs are mounted into the wall even during masonry. The Mauerlat beam is treated with an antifungal agent so that it is not subject to destruction.

5. When everything is ready for the installation of rafter legs, it is important to mark the base where they will be attached. Ready-made rafter legs can be ordered in the workshop and then assembled on their own, than spending a lot of time on their manufacture. For convenience, they can be expanded from those sides of the house, where they will fit along the perimeter of the attic.

6. Check the struts for looseness and vertical movement. If it is, then do not think that the problem will go away with the installation of roofing materials. The added weight of the structure will only make it more wobbly. Therefore, all flaws should be eliminated even at this stage – reinforce the fastening with braces and ties.

7. Experts recommend observing an equal interval (step) between the rafters – about 80-120 cm. The easiest way is to pull the twine between the extreme rafters to use it as a markup and level of the remaining rafter beams. Racks are made not only in one horizontal plane, but also set exactly vertically – check the plumb line.

8. The uprights are a good foundation for the future walls of the attic living space, so they should be perfectly flat. Inside there will be cladding made of wood or plywood boards, drywall, fiberboard or chipboard. Do not forget to put the appropriate insulation between them, which is intended for the roof and attic..

9. To fix the racks to the drains of the upper bar, use metal staples or nails. With the completion of this stage of work, the installation of the rafter frame is completed. At the last stage, the rafters are connected in pairs, attached to the ridge beam.

10. Remember to leave openings for skylights or doorways for stairs. Installation of roof windows is carried out after the walls of the inner lining are equipped..

11. It is possible to do without a ridge beam, but it is necessary when the length of the attic roof is more than 7m. But it increases the total weight of the rafter system. It is enough to fasten the tops of the rafters with ties. The final stage is the lathing for heat and waterproofing and roofing materials. When the roof is almost ready, proceed to the installation of roof windows and interior decoration of the room..

12. It is better to calculate the amount of consumables and wooden beams in advance using tables and drawings, but it is better to take into account the minimum and maximum consumption – with different steps between the racks. Ideally, the design is expected to be lightweight and reliable at low cost. We suggest studying the important points of arranging the roof truss system in the video at the end of the article.

A structurally complex attic under aesthetic roofing materials looks much more interesting than an ordinary hip roof, but only specialists can make it. When the decision is made to replace the old roof with a more modern roof, take the opportunity to build an attic. Although the more complex structure of the roof truss system is a bit onerous in terms of the amount of work, the additional living space and the unique look of the house will delight your children and grandchildren for many years..