The foundations for roofs made of roll materials must be carried out especially carefully. They can be made of wood, from load-bearing monolithic or prefabricated reinforced concrete slabs or in the form of cement-sand or asphalt concrete screed on an uneven reinforced concrete base or insulation.
The wooden base is arranged in the form of two wooden floorings: the lower flooring, called the working floor, is made of 22 mm thick planks, which are laid along the supporting structures of the roof at a distance of no more than 30 cm from each other; the upper deck, called continuous, is made of antiseptic boards measuring 20×50 mm, nailed to the working deck at an angle of 45 °. The base should not have slots and holes from fallen knots, as well as sags and protrusions. Wooden flooring is covered with bitumen mastic (Fig. 1).
Fig. 1. Rolled roofing device on a solid plank lathing: 1 – working flooring; 2 – protective flooring; 3 – bare roofing material; 4 – roofing material; 5 – mastic; 6 – roofing steel; 7 – strip of roofing material.
Rolled roofing device on a cement-sand screed. As a base for a roll coating, a screed is used from a cement-sand mortar of a grade of at least 50, a composition of 1: 2 or 1: 3 by weight with the introduction of antifreeze additives – potash (calcium chloride) or sodium carbonate salts in an amount of 10 … 15% by weight of cement, as well as non-cast sandy asphalt concrete, the compressive strength of which should not be lower than 0.8 MPa. The thickness of the screeds when laying on concrete is 10 … 15 mm, on rigid monolithic slabs – 15 … 25 mm, on bulk insulation – 25 … 30 mm. If the asphalt concrete is laid on a loose insulation, it settles or cracks along with the rolled carpet. Asphalt concrete is used for screeding only on slope planes. Screeds on vertical and steep planes, such as parapets or auxiliary walls, are made of cement-sand mortars or concrete tiles. When installing screeds from a cement-sand mortar, every 6 m, temperature-shrinkage joints are left, limiting the screed itself and having the shape of squares with sides of 4×4 m.To form temperature-shrinkage joints when installing the screed, wooden slats with a thickness of 10 mm are laid, which are then removed, and the seams are sealed with roofing mastic and sealed with a strip of roll material.
The surface of the base is leveled, all potholes and sinks are sealed with cold bituminous primers. As a primer, a solution of bitumen BN-70/30 in a slowly evaporating solvent – kerosene or diesel oil in a ratio of 1: (2 … 3) is used. A freshly laid screed solution is impregnated with bitumen to a depth of at least 3 mm, and a film forms on the screed surface, which prevents water from evaporating from the solution. The drying time of the primer on hardened screeds is 12 hours, on freshly laid screeds – at least 48 hours. Before priming, the base is cleaned of debris and dust. The base is primed by spraying with a cold soil composition. The first layer is placed on a completely dry surface. Priming is carried out in strips of 3 … 4 m wide.
A cement-sand screed is arranged by laying a cement-sand mortar with a strip width of up to 2 m. The surface of the laid mortar is leveled with a rule or a trowel (Fig. 2). The next strip of cement-sand mortar is laid after the previous one has set. Before performing the screed, it is necessary to complete the device of all parapets, ventilation and other shafts, exits to the roof.
Fig. 2. Screed device on lighthouse rails: a – leveling of cement-sand mortar; b – rule; 1 – lighthouse rail; 2 – a fresh strip of screed; 3 – rule; 4 – box with solution; 5 – finished screed; 6 – intermediate strips filled with mortar after removing the lighthouse rails.
In the places where the screed is adjacent to the parts of the building protruding above the roof and on the bends of the roof base, transitional sloped sides of 150 mm wide are made at an angle of 45 °, rounding them for better gluing of the rolled carpet (Fig. 3, 4). Before starting work around the screed zone, inventory fences are installed on the slopes of the coverings. Board boards are nailed along the overhangs.
Fig. 3. Arrangement of roof abutments made of roll materials: a – roof abutment to walls; b – the same, flat roof to the parapet; 1 – rolled waterproofing carpet; 2 – screed; 3 – additional layers of carpet; 4 – board made of mortar or concrete; 5 – wooden cork; 6 – cement-sand mortar; 7 – standing clamp; 8 – protective apron; 9 – protective gravel layer.
Fig. 4. The intersection of the combined roof with a free-standing rack: 1 – bearing panel; 2 – roll-up waterproofing carpet; 3 – grouting; 4 – vapor-permeable layer; 5 – rack; 6 – metal apron; 7 – standing clamp.