Defects, roof repair and reconstruction
Structural features of roof repair (the presence of shallow valleys, parapets, structural elements protruding above the roof), lack of sufficient ventilation of the attic space, etc. The unsatisfactory condition of the coating leads to an increased humidity regime of the wooden elements of the rafter system and the attic overlap and premature wear.
The following defects in the rafter system are most common: cracks (delamination) of the rafter and extra legs, chips in nodal junctions, deflections of rafter legs, girders, rot in structural elements of rafters, loosening of bolted and nail joints.
The types and volumes of roof repair work must correspond to both the technical condition of the roof itself and the technical condition of the main load-bearing replaceable and non-replaceable structural elements of the building. As noted above, the main purpose of the roof repair of the building is to protect against the influence of atmospheric precipitation, especially rain, as well as to maintain a certain heat and humidity regime, which contributes to the long-term preservation of the structural elements of the building.
The types of roof repair work largely depend on the technical condition of the roof covering of the load-bearing elements of the roof, the terms of their operation, the residual life of the building as a whole. The standard service life of wooden rafters in accordance with the regulation on preventive maintenance of residential and public buildings is 50 years.
The exception is roofed with a complex configuration with a large number of valleys, parapets, and elements protruding above the roof; chimneys, ventilation shafts, sewer pipes, etc. High-quality operation of roofs, timely preventive maintenance of the roof covering, creation of a normal thermal and humidity regime of the attic floor, periodic treatment of wooden elements with an antiseptic – all this contributes to a significant increase in the service life of roof elements.
A complete replacement of the rafters must be done only with sufficient technical justification and with a technically unsatisfactory condition of the bearing elements or, if necessary, complete replacement of wooden floors with precast reinforced concrete. Dismantling the roof or in roof repair for a long period of time is extremely undesirable, as it leads to intensive wear of the main bearing structural elements of the building.
Most often, the following types of work are performed when repairing roofs :
– partial replacement of the battens;
– reinforcement of the lathing by filing from the inside of the unloading system, consisting of boards laid across the lathing and a bar laid between the rafter legs and attached to them;
– partial change of individual boards in the area of eaves and valleys;
– replacement of individual sections of the Mauerlat;
– change in some places of the ends of the rafter legs with the setting of “prostheses”;
– reinforcement of rafter and extra (diagonal) legs by patching on both sides of the boards or by installing racks, struts;
– strengthening of the junction points of the truss systems;
– installation of additional bolts, brackets, metal or wooden linings;
– creation of effective ventilation of the attic.
The practice of roof repair covered with sheet steel in the autumn-winter period of the year has shown that snow melting on the roof does not occur when the temperature difference between the outside air and the air in the attic is 2-4 ° C. The required temperature difference is achieved as a ventilation device in the attic space through the skylights. Ventilation near-eaves and ridge vents, as well as ensuring sufficient thermal insulation of the attic floor, pipelines passing through the attic, ventilation shafts, and ducts.
The cross-sectional area of the skylights and roof vents should be at least 1/300 – 1/500 of the attic floor area. At the same time, the location of these devices should ensure end-to-end ventilation of the attic, excluding local stagnation (air bags). The eaves vents are made in the form of a gap between the brick and the roof (slot vents) 2-2.5 cm wide, or separate holes 20×20 cm in size are arranged in the eaves part of the wall with the obligatory installation of a lattice. The ridge vents are made either in the form of a continuous slot 5 cm wide or in the form of separate holes (weather vans) every 6-8 m. The
eaves supply slots under
the eaves overhang are made in the following technological sequence : – in the eaves zone, the roof of steel sheets and the fence are removed;
– dismantle the solid wooden flooring of the eaves;
– Sewing a lining pine wedge of a given size onto the filly of the rafter leg;
– restoring the continuous flooring of the eaves with the replacement of individual damaged boards and the roof of the eaves made of steel sheets with wall gutters and a fence;
– seal the folds of the roof, the supporting parts of the fence posts.
If the temperature difference is higher than the established indicator, it is necessary to establish sources of heat supply to the attic, which may be :
– insufficient thermal protection of the attic floor; – low-quality thermal insulation of heating and hot water supply pipelines, ventilation ducts, mines, etc.
The thickness of the insulation of the attic floor is determined by measuring its temperature with a thermometer immersed to a depth of 2 cm.