Bratex modular roof tiles part 3

functionality

What is the tile screwed on to?

The metal roof tiles are attached to the wooden substrate, i.e. the substructure, with wood screws with a self-vulcanizing gasket ensuring tightness (so-called farmer screws). These are 4,8×35 mm fasteners with an M8 head and a tip in the form of a drill whose task is to drill through the surface of the sheet. The screwdriver is attached to the so-called bit, i.e. a magnetic M8 tip that holds and tightens the screws. It is customary to apply a screwdriver with a screw to the sheet metal surface and fire the trigger (adjust the clutch of the device beforehand). Due to the flat and slippery varnished surface to which the screw is applied and the pressure of the screwdriver on the screw, sometimes the screw drill bit slips off the surface before the sheet is drilled. Unfortunately, then the varnish is scratched, which after finishing the work should be protected with mortar paint. It is worth noting that a medium-sized roof of 200 m1200 requires the use of approx. XNUMX screws, so the risk of scratches increases with the number.

A similar situation applies to the transverse and frontal joining of the sheets to each other. Fasteners for sheet metal 4,8 × 19 mm are used. It is worth noting here that these fasteners have a smaller thread pitch and the thread reaches the very screw head - this is an important feature of the fastener for sewing sheet metal. In addition, butt joints are more demanding for the contractor than applying fasteners to the sheet from the top.

Fixing with screws

Unlike flat roofing without embossing (e.g. trapezoidal sheet, standing seam), fixing a metal roof tile requires paying attention to several issues. The figure below shows how the fastener is applied to the metal roofing tile.

The screw must be placed in the place provided by the manufacturer. It is customary to use 5-6 screws per square meter. The most optimal place for the connector is the lowest point of the wave and the position relatively close to the embossing.
Thanks to this, tightening the fastener with the adjusted screwdriver clutch will not cause deformation of the sheet surface around the fastener. Why is there such a risk? As shown in the drawing, due to the embossing on the metal roofing tiles, the screw is always located at a certain distance from the embossing, which in turn causes the sheet to be higher than the wooden substrate by about 2-4mm. The closer the sheet is to the substrate, the more rigid the surface of the sheet is. The further you go, the greater the risk of deformation when the screw is tightened with a force regulated by the screwdriver clutch. In addition, a screw that is further than 2,5-3,5 cm from the embossing becomes noticeable.
The position of the fastener at the lowest point of the wave is conducive to the fact that it will be applied perpendicularly to the substrate and its seal will best adhere to the surface of the sheet.

It is worth noting that the metal filings formed after drilling the surface should be swept away immediately. They are heated to a very high temperature and can damage the varnish, and later become a focus of sheet metal degradation.

To sum up, incorrect use of fasteners exposes the roof to leaks, significantly disturbs the harmony of aesthetics and may be the cause of other subsequent defects on the roof.

A helpful feature of Bratex modular metal roof tiles

Bratex modular metal roofing sheets have a useful factory feature - recessed assembly points, Bratex's proprietary solution, developed and implemented with the Scandinavia metal roofing tile in 2015. These are horizontal and vertical points on the surface of the sheet (red in the picture) and from the face on its embossing (yellow in the picture).

Recessed mounting points are not holes that require a screw to prevent leaks. These are depressions in the surface of the sheet profiled for the drill bit of the farm screw.

Placing the fastener in such a recess makes it "sit down" more stable and firing the screwdriver's trigger becomes more reliable that the screw will not fall out of place, will not scratch the surface of the sheet and will be screwed in at the first attempt.

A similar situation applies to recessed mounting points located on the end face of the sheets, on the ribs. There, the application of screws is even more demanding, because the contractor has to set the screwdriver horizontally and brace himself. In the Bratex Scandinavia modular metal roof tile, the location of the recessed assembly points on the front was designed at an angle and on the upper wave.

There are two important reasons. The first reason that forced the fully curved profile of the metal roof tile was the full adhesion of the self-vulcanizing gasket, because the screw is at an angle. The second reason is the certainty that in the case of not tightening the fastener or using a wood fastener (incorrect type) that has been twisted, there will be no leakage in this place, because the location of the screw is not in the lower wave, i.e. in the place of water flow.

benefits

Recessed mounting points are visual instructions for the contractor where the manufacturer has provided for the use of the fastener. Recessed mounting points eliminate the risk of scratching the surface of the sheet metal by the screw, because its drill "sits" in the recessed point like in a matching socket. The mounting points are located in the optimal place so that they are as little visible as possible and do not pose a risk of sheet deformation during the final stage of tightening with a screwdriver. It is worth noting that due to the specificity of a particular roof and battens arrangement, it may be necessary to screw the fastener in a different place than the marked point, or there will be no need to screw it into a recessed assembly point. There are no contraindications in any of the described cases.

Savanna flat metal tile

The drawing presented earlier shows how the screws are arranged after assembly to the metal roofing sheet. Some of you have a question, what about tightening sheets of products with flat surface characteristics, such as the Savanna modular metal roof tile? Will there be deformation of the whole sheet or part of it?

Sheets of longitudinally profiled modular roof tiles with arches, such as Bratex Scandinavia or Aurora, are simply stiffer. Screw application poses no risk of profile deformation due to tightening. On the other hand, sheets of a flat product, such as the Bratex Savanna modular metal roof tile, are a completely different matter. The sheets of this metal roof tile have four completely flat segments, which, if screwed on according to the previously described assumptions, would result in deformation of the flat surface.

When designing this metal roofing tile, we introduced Bratex Step-Mont's proprietary solution consisting in the fact that the first 3 cm of the sheet, right after the embossment in the direction of the roof slope, adheres to the batten, the sheet is simply parallel to the ground.

As a result, we obtain the best possible surface for applying the fastener, which is rigid and does not affect the flat surface of the sheet in any way. This is the so-called additional pressing.

Sheets of Bratex modular roof tiles – Scandinavia, Savanna and Aurora – have pre-prepared recessed mounting points on the top of the sheet and on the front (on the embossing).

Read the article Bratex modular roof tiles part 1

Read the article Bratex modular roof tiles part 2