- Features of soft tiles
- Rafter system and lathing
- Preparation for installation: materials and tools
- Underlay and abutments
- Correct installation technique for shingles
- Joints: skates, cornices and roof cuts
Today we will get acquainted with bitumen shingles in more detail, and find out which installation technique is considered correct. The soft roof is very firmly entrenched in construction practice, nevertheless, most of the work on its installation and laying is carried out in violation of technological rules.
Features of soft tiles
Bituminous shingles can rightfully be considered a unique roof covering. Providing excellent waterproofing, it also has an excellent appearance and allows complex roofs to be equipped even with very complex configurations. However, for the device of a bituminous roof from piece elements, one should thoroughly know the principle of operation of such a coating and a number of specific nuances.
The structure of the bituminous tile: 1 – self-adhesive layer; 2 – modified bitumen; 3 – reinforcing layer (fiberglass); 4 – mineral dressing
The main element of soft tiles is called shingles. It is a strip of one meter length, 30–35 cm wide, and consists of two parts. In the upper part of the shingle there is a rectangular belt, which provides reliable protection against the leakage of stagnant water even on gentle slopes. The lower part in the form of teeth has a protective and decorative function, it covers the belts of the elements of the lower row, while it itself has a powder of mineral granulate that protects the tiles from ice, sunlight and mechanical damage. Due to the overlap of the shingles on each other and their high-quality gluing, excellent protection against moisture and isolation of the fasteners from the atmosphere is provided.
With all its advantages, soft tiles have a complex installation technology, which may have specific differences depending on the format and type of shingles. The basis for understanding the nuances of installation is the manufacturer’s instructions. It indicates the layout of the fasteners, the order of laying, as well as the entire technical process for making connections and installing protective elements of the roof.
Rafter system and lathing
Soft shingles can only be placed on solid sheathing. It does not have to be a tongue-and-groove flooring; sheathing of the rafter system with sheet materials is more preferable. Of the latter, we recommend OSB 3 and 4 moisture resistance classes or moisture-resistant plywood with a thickness of 12 mm or more with an increased pitch of the rafter legs. The content of formaldehyde resins in the boards does not play any role. If a boardwalk is installed, the wood should be placed with the narrow side of the knots up, so that if they are squeezed out, no blisters will form on the covering. Boards are attached to each support with self-tapping screws with a grip depth of at least 60 mm, in each node there are two attachment points.
Plates are screwed directly to the rafter legs or trusses so that the joints are as close to the center of the supports as possible. Horizontal joints are fastened by installing additional jumpers under the bottom. Sheet materials can be fastened with self-tapping screws or brushed nails from 50 mm, the step of fastening the flat part is not more than 30 cm, the edges – up to 15 cm.If you plan to insulate the roof, a windproof vapor-transparent membrane is rolled out in front of the sheet sheathing, a counter-rail with a thickness of 25 mm is filled, and then stretched waterproofing film. Due to the counter rails, air is formed, which comes out from the bottom to the drip bar, in the upper part of the slopes, an exhaust ridge groove is equipped or ventilation vents are installed.
Close attention should be paid to making the joints between the slabs. Here it is imperative to leave an expansion gap of 3-5 mm for free expansion of the material from fluctuations in humidity and temperature. All joints must subsequently be filled with molten bitumen or coated with cold mastic. The OSB surface must be inspected for loose chips, protruding fastener caps, if necessary, a rough abrasive roughing must be performed.
Preparation for installation: materials and tools
The device of a high-quality roofing made of bituminous tiles is impossible without an appropriate material base. In addition to the shingles themselves and the underlay, a significant amount of bitumen mastic or bitumen elastomer glue will be required. Also, there should be sufficient carpets for cornices and valleys, ridge tiles, wind and cornice strips. Bituminous roofing is very vulnerable to bad weather, therefore, the protection of the abutments must be performed immediately after the installation of the coating, which means that all the materials necessary for this should be available.
The necessary tools can be divided into two groups: special and general purpose. From the category of the latter, you will need spatulas and brushes of various sizes, a sectional assembly knife, a hammer, a pry bar with a nailer, a screwdriver, a syringe gun and metal scissors. Marking tools are also needed: a dyeing line, a mooring line, chalk and a tape measure of sufficient length. From special tools, a curved knife is required, designed for cutting tiles and underlay, as well as a nailer. It will not be possible to do without the use of an electric construction hair dryer, which heats the glue on the adjacent surfaces of the shingles.
Tool for laying flexible tiles: 1 – spatulas; 2 – paint brushes; 3 – assembly knife; 4 – hammer; 5 – mount; 6 – screwdriver; 7 – sealant gun; 8 – scissors for metal; 9 – chopping cord; 10 – tape measure; 11 – nailer; 12 – a knife for bituminous tiles; 13 – building hair dryer; 14 – safety belt
There is a lot of controversy about whether it is compulsory to use an automatic nailer. In fact, high-quality installation can only be performed using a nailer. The fact is that the varnish that holds the nails in the cassette melts when hammered and firmly adheres to the adjacent materials. At the same time, the galvanizing of the fastening element is not disturbed and no vulnerable spots are formed at the attachment point, respectively, the appearance of leaks over time is guaranteed to be excluded..
It will not be superfluous to emphasize the importance of ensuring safety during roofing work. On slopes with a slope of more than 7 °, it is allowed to work only in safety belts, while scaffolding should be erected under slopes with a slope of more than 20 °. On roofs with a slope of 30 ° or more, only ladders can be operated.
Underlay and abutments
It may seem that shingles by themselves provide absolute protection against leaks, but they are not. Firstly, absolute waterproofing cannot be guaranteed at the edges of the coating, and secondly, even on flat areas with a small slope, melting ice will inevitably form, and over time, water will surely find its way into the depths of the cake. Therefore, a lining carpet should be arranged under the tiles – an additional measure of protection against wetting of the sheathing and the supporting system.
On roofs with a slope of more than 20 °, the lining carpet is placed in one strip along the edge of the eaves, along the edge of the wind overhang, on both sides of the ridge and valley. On more gentle slopes, the carpet should be laid over the entire area of the slope, providing an overlap between the canvases of at least 10-15 cm. The carpet can be rolled horizontally, starting from the bottom of the slope, or vertically. The latter is preferable on steeply sloping roofs, where the material straightens well under its own weight and does not wrinkle when fixed. Regardless of the direction of installation, the underlay carpets are rolled out first in the valleys, and the roof cuts are waterproofed. In this case, the water protection of the main planes is allowed over the valleys and abutments to a width of about 15-20 cm.
Laying the carpet is accompanied by sealing all joints. The overlaps between the canvases must be coated with elastomeric glue, especially for the areas of the carpet that are adhered to the waterproofing of valleys and cuts. The carpet is fastened to the base mechanically – with brushed galvanized nails from 20 mm long with a pitch of 20–25 cm and a distance of 6–8 cm from the edge. The line of attachment of each row is covered with the edge of the overlying canvas. In the lower part of the slope, the eaves overhang is trimmed with a metal strip with a fastening step of 100 mm in a checkerboard pattern. On the roof overhangs, a beading should be nailed in the form of a glazing bead 40–50 mm wide. At the same time, the carpet should fit tightly to the board and tuck under the wind overhang. It is imperative to bring the waterproofing of the main planes close to the bend of the ridge, and then cover both slopes with a common canvas at least 200 mm wide on each side, while all adjoining parts must be glued.
Correct installation technique for shingles
The outer layer of the roof includes other elements in addition to shingles. The carpets of the valleys are always installed first, they are nailed with an indent from the edge of about 40 mm with a step of 15 cm, the edges are carefully coated with hardening bitumen mastic. After that, installation of rectangular curtain shingles is carried out, which should recede from the corner of the protective strip by 5-10 mm and be reliably glued to the metal.
When all junctions are protected, the coating is laid on the main planes. To do this, it is imperative to mix shingles from different packages in order to avoid large-scale manifestations of color mismatch. Depending on the type of shingle, the order and direction of installation may differ, but in any case, the shingles are stacked strictly sequentially. Fastening of each element is carried out at four points, and if necessary, increased resistance to wind loads – in six places with equal indents. The adjoining parts in all places where the shingles overlap are heated to activate the glue and pressed tightly against each other; in winter, an additional layer of glue is applied. Shingles need to cover the entire area of the slope close to the ridge and ends, and in the valleys – up to a conditional line retreating from the center of the gutter by 100-120 mm.
Joints: skates, cornices and roof cuts
To cover the skates, a special ridge tile is used, each shingle of which is attached to glue and nails, while the next element hermetically covers the attachment point of the previous one. Immediately after finishing the ridge on the open ends of the roof slopes, the covering is trimmed with a slight offset from the edge and must be nailed. Then the assembly is covered with an outer end protective strip.
Flexible roofing is renowned for its ability to cover complex roofs with a minimum amount of waste, an advantage especially useful when sealing roof gaps for chimney and ventilation pipes. Household communications are usually combined into groups of 2-3 channels, which are enclosed in a rigid neck made of timber and plywood. Both the lining carpet and the bituminous roof covering are laid with an overlap on the neck, raising the edges to a height of at least 25 cm from the slope. After that, the carpet and shingles must be carefully glued and nailed to the neck, and the cuts must be tarred with mastic. The entire junction unit is subsequently covered with a protective apron made of roofing iron.
Separate vents are easier to work with. For them, special roof cuts are used – sealing necks with wide cuffs, which are designed for different angles of the roof slope and the diameter of the leads. This kind of reinforcement is mounted immediately before laying the carpet, then all layers of the coating adjacent to the cutting are carefully sealed with glue.