Metal roof: checkerboard or scale roof

Recommendation points

• What is the coating
• Preparing the cake and crate
• Roof waterproofing
• Manufacturing of piece elements
• Coating installation
• Adjacency protection

One of the most original types of roofing is metal tiles. But not the one that is supplied and mounted with panels, but from piece elements. Such a roof covering technology is called checkerboard or flake and in this review we will tell you about it in detail..

What is the coating

A checkerboard roof is not the know-how of folk craftsmen. This type of coating has been known for a very long time, although it has not received widespread distribution due to the high requirements for the qualifications of the roofer. However, scaly roofing was ideal where other materials could only be used with great difficulty. For example, when finishing roofs of complex shapes or domes, and especially when the strength of the supporting system is low, because metal blocks greatly benefit from the weight of most traditional coatings.

The climax of the glory of this roof was the era of the Renaissance culture, where the emphasis on the remarkableness and value of the building was often placed precisely due to the domed shape of the roofs. Of the youngest architectural monuments, where checker roofing was used, one can cite the building of the City Hall of Milwaukee in Wisconsin or Berlin Cathedral. It is rumored that the famous dome of the Cathedral of Santa Maria del Fiore was once covered with a checkered roof, but after a while the coating was replaced back due to the fact that with the darkening of the color it violated the image conceived by Brunelleschi.

During the Renaissance and Baroque epochs, elements of the checkerboard roof were made of copper. Today, valuable metal is also used, but cheaper analogs have appeared, for example, galvanized steel with a polymer coating. Triangular, trapezoidal or rhomboid blanks are first cut from sheet material. Further, the edges of the blanks are bent in a certain way, forming recumbent folded locks for joining with neighboring elements. It is noteworthy that roofing scales can be manufactured both in a factory way and directly at the facility..

Preparing the cake and crate

Like most types of tiled roofs, it is better to mount a checkerboard on a solid sheathing. There are two options for the device of the latter, depending on whether the roof is insulated. In general, the difference between the types of lathing is the presence of a ventilation gap under the coating.

The sheathing made of sheet materials is ideal for cold roofs. The rafter system is simply sheathed with moisture-resistant plywood sheets or chipboards, leaving deformation gaps at the joints of 3-5 mm. Waterproofing is first mounted on the formed surface, then the coating elements are attached. Such a lathing device is also possible in the presence of insulation, but only if the steam protection of the cake from the inside is properly organized.

Decking made of 20×80 mm planks, laid with an offset of 15–20 mm, is also a good option. Due to the gaps in the crate, a message appears between the under-roof space and the internal cavities of the scales, which ensures the evaporation of moisture condensing on the back surface of the metal. This crate is more complicated for two reasons. First, on the rafter legs, you first need to lay a superdiffusion membrane that allows water vapor to pass in only one direction and retains condensed moisture. That is, before installing the crate, first, counter-rails are installed on the rafter legs..

Secondly, it is necessary to maintain the step of the transverse lathing in accordance with the dimensions of the roofing elements, otherwise there is a high probability that the place of attachment of the next row will fall on the gap between the boards. However, despite the complexity, this version of the crate for a warm roof is the most durable and, in general, technologically correct..

As for the insulation cake, everything is classic here. Usually, the roofing insulation is laid between the rafters after the installation of the sheathing. Plates are temporarily fixed with a “snake” made of wire or mounting tape, after which, if necessary, you can make the inner lining. Here, there is a difference in the performance of the crate made of slabs or boards: when insulating the roof, the ventilation gap must be provided at least from one side, but it is more difficult to do this from the inside, especially without damaging the vapor protection.

Roof waterproofing

The scaly coating has a protective and decorative function, while not being the only barrier to water. More precisely, the checker roof removes most of the precipitation over the surface, however, numerous small leaks are a characteristic disadvantage of almost all types of roofs made of piece elements.

Waterproofing for a checkerboard roof is made of bitumen roll materials based on paper or fiberglass. Since the strength for such waterproofing means less than its localizing ability, expensive glass insulation can be abandoned in favor of euroruberoid. Materials based on PVC and polyethylene are also well recommended. Rolls of waterproofing during installation are rolled vertically, providing an overlap between the canvases, recommended by the manufacturer for the existing slope angle of the slopes.

The peculiarity of waterproofing a checkerboard roof when performing a sheathing of boards is that a hydro-barrier (superdiffusion membrane) is located under them. At the same time, the transverse slats, to which the scales are attached, are necessarily treated with fire and bioprotective impregnations, and subsequently with a water-repellent primer. Thus, a checkerboard roof is that rare case when part of the load-bearing system of an insulated roof is operated with outdoor humidity..

Manufacturing of piece elements

For large flat slopes, it is better to order a checkerboard roof at the nearest factory for the manufacture of metal tiles and profiled sheets. However, for small objects such as gazebos, outbuildings and well houses, you can get carried away and make your own scales from available material. It can even be an ordinary galvanized sheet, in the end, the appearance will still be amazing.

Before buying a material, you need to calculate its quantity. This is done by examining the unfolding of the element. The middle part that forms the cover is the usable area, while the flanges and locks can be considered as collateral losses. Having calculated what is the ratio of these two values ​​on a separate element, you can approximate it to the total area of ​​the roof, providing the necessary margin. It is also important to study which method of marking blanks on a sheet will entail the least number of illiquid scraps.

For example, you can take a flat and volumetric roof block with a workpiece size of 300×300 mm. Initially, you need to do the marking and trimming of the blanks. The unfolding of a flat checker has the form of a square, on all sides of which, with an indent of 20 mm, marking lines are drawn. Three corners of the workpiece are cut at 45 °, the cutting line passes through the corner of the internal marking. The fourth corner looks like a rectangular tongue 20x20mm, in the center of which a hole is cut. The tongue is formed by a cut in the form of a rectangular triangle 20×20 mm, the legs of which pass along the edge of the part and the tongue itself.

The reamer for a three-dimensional checker has a slightly more complex form. The corner with the tongue and the adjacent edges are marked as described above. But the opposite corner looks different: there are two lines along the edges with an indent of 20 and 40 mm. The initial trimming of the part is done with oblique lines that converge at an angle opposite to the tongue. In this case, on the reverse side, the cutting line is connected to the edge of the indentation line of 20 mm. All three corners are cut at 45 ° to a width of 40 mm, while at the corner opposite the tongue, the edges are additionally trimmed so that in the widest part the wedge-shaped trims are not 4–5 mm wide. Also, at this angle, it is necessary to make an incision diagonally up to the convergence of the marking lines of an indent of 40 mm, and then undercut the notch along one of these lines.

The bending of a flat cup is carried out along the indentation lines of 20 mm. The edges adjacent to the tongue are bent outward at 180 °, the other two inward at the same angle. The edges adjacent to the tongue of the volume block are also bent outward at an angle of 180 °. At the same time, a double fold is made on two opposite edges: first, at 90 ° inward, the edges are folded along the 40 mm indent lines remaining after marking, and then again at a right angle, the edge is wrapped 20 mm from the cut line.

It is possible to make up to 100 elements of a checkerboard roof if you only have a mallet with a mandrel; you can speed up the process with a manual edge bending machine. With a larger volume of work, a stationary listogib will not interfere, while it is desirable that the tool has an open angle. Professional roofers for the manufacture of such a coating use corner bending machines, thus, due to the bending of two edges in one installation and a system of stops, accurate compliance with dimensions and geometry is guaranteed.

Coating installation

Covering the roof with checkers is quite simple. Installation of elements is carried out from the bottom of the ramp strictly in rows. In this case, the eaves and wind overhangs are finished, as when laying bituminous shingles: with a metal protective strip, the width of which should be 4-5 cm more than the diagonal of the piece element.

Each checker is located with the tongue up, its initial fastening is performed with a galvanized self-tapping screw with a press washer. The first block must be fastened on the left side of the slope so that the distance from the corner of the cornice strip is about 10 mm and the same amount from the edge of the frontal board. Before fastening the elements of the lower row, a clamp is screwed to the edge of the slope, for which the checker is held by the edges bent under itself. Additionally, using clamps or conventional folded strips of roofing iron, the folded edges are fixed at a height of about 20 mm from the center of the element. Thus, the entire first row is typed..

In the second row, the checkers are offset by half the width of the element. The V-shaped depressions of the first row have two converging bent edges, for which it is enough to simply hook the element to be installed, so that fastening the lower edge to the clamp is no longer required. But additional fastening with clamps on the sides of the checker should still be done.

Adjacency protection

With the main planes, everything is quite simple, but how to correctly close the covering on the roof outlets, arrange skates and valleys? To perform each of these technological connections, its own procedure is provided..

The most simple with wind outreach. For them, the checker is cut vertically into two parts. The right side is used as an addition to the left edge and vice versa. The halves of the checkers are attached both with a standard lock and with a pair of self-tapping screws 15–20 mm from the edge. Subsequently, the roof edge is covered with a protective strip.

With the skate, everything is similar, with the only difference that the checker is not cut after production, just special elements are bent from the blanks divided into two parts. For the upper final row of checkers, you usually need to make two types of addons. In the former, the upper corners are truncated along the ridge line, the entire row is fastened with self-tapping screws 10–15 mm from the edge with a step of about 80–100 mm. The second type of completions is made from the remains of the first type of blank. As a result, you get cut off the bottom corners of a standard checker with two edges bent inward. These elements close the main waterproofing of the ramp.

Flattening the slopes in the valleys is the most difficult task, which, however, is typical for most types of surfaces. You cannot do without the lower gutter of the valley, it is bent from the roofing iron to match the color of the coating, while the width of the shelves should be 6-7 cm larger than the diagonal of the checkers. The checkers along the valley are adjusted manually in each row. A mooring is pulled in the center of the gutter, from which both sides of the coating are marked and trimmed. The checkers are trimmed with a margin, so that later it is possible to bend the trimmed edge inward to form an edge of at least 20 mm. In this case, the total undercut line should be approximately 10-15 mm away from the berth. After that, the valley is covered with an external gutter, which has mainly a purely decorative function..