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The present state of technology

The Regulations of the Central Association of German Roofers from 1997 titled "Regeln für Dachdeckungen mit Schiefer" (The Rules of Roof-laying with Natural Slate) and the relevant parts of the Hungarian Standards Regulations meet the highest standards of the present state of technology. Tető-Horn observes the regulations (and has them observed) by following the principles above.

Incline
In general, regarding the various tiling methods, the inclination of rafters and eave stabilizers can take their values between the following limits:
1. in case of the old German method it must not be below 25°(47%). In special cases, with careful circumspection, it can go as low as 23° (42%) on smaller surfaces (standing roof windows, canopies etc.).
2. regarding the old German double roofing it must not be below 22°(40%). In special cases, with careful circumspection, it can go as low as 20°-ig (36%) on smaller surfaces (standing roof windows, canopies etc.).
3. considering the German imbricated slate roofing it must not be below 25°(47%).
4. respecting the German double imbricated slate roofing it must not go below 22°(40%).
5. as for the regular double roofing it must not be below 22°(40%). In special cases, with careful circumspection, it can go as low as 20°-ig (36%) on smaller surfaces (standing roof windows, canopies etc.).
6. as regards the standard roofing with curved-end slates (bogenschnitt) it must not go below 25°(47%). The overlap of rows, the position of the building, the given climatic conditions and the length of the rafter have to be taken into account. In case of roof inclinations between 25° and 35° the dominant direction of the wind is to be taken account.
7. considering regular roofing with slates of various shape it must not be under 30°(58%). Lower inclines can be chosen only if the building site and its climatic conditions permit it. These pitch angle values can be lower - max. 15° - only if a water shield is also installed on the roof. In case of particularly long rafters, high wind areas or other adverse climatic conditions the lower limit of the incline must be higher than the general pitch values specified above.

Underlayment
A wooden sheeting with a thickness of at least 25 mm must be used as underlayment. The boards must have an undamaged edge, be dry and must not be sagging. The wooden material is to meet the quality regulations of the Hungarian Standards or those of the EU. The sheeting should not be thinner than 12 cm, except the boards that are grooved cone-shaped at reglets (usually placed vertically to the eaves gutter). Boards thicker than 15 cm must be secured on each rafter with three nails or pins which must be at least 2.5 times longer than the width of the board.

If the rafters are positioned more than 60 cm away from each other, then the sheeting must be thicker or must be reinforced with battens.

In case of lathwork full-surface sheetings have to be used at the ridge and the eaves.

In case of wall tiling the maximal distance of brandering is 60 cm. Fixing to the wall or to concrete is done with dowels, screws or by other proper fastening methods.

The underlayment to a slate roof can also be nailing panel boards or nailing masonry (e.g. pumice stone, honeycomb concrete, wood cement etc.) You should be careful with selecting the right nails or pins. Direct nailing to panel boards or masonry is possible since the slate, due to its natural structure, lets gaseous moisture diffusing in the wall escape at any point of the coverage.

In case of nailing wood lathing the battens should be at least 40x60 mm big. The same applies to the lathing on the roof as well.

In case of regular roofing done with hooks the tiles come on a min. 24x28 mm battening and the distance between the rafters, the wind and the snow load must be taken into account. Regarding wooden lining the dimensioning of the wood, the heat and damp calculations have to be made in accordance with the Hungarian Standards.
Considering other fastening methods, such as aluminium structures, the carrying capacity must be verified.

Fixation

The slates can be fixed best by galvanized or wrought roofing nails. You can also use slate pins, quality-steel screw-nails or copper nails. In case of copper nails the shank should be roughened or like that of a screw-nail.

When laying the roof, in the case of the German roofing methods the fixation (nailing) should be done with at least 3 roofing nails per slate if the slates are positioned higher than 24 cm. If not, then 2 nails are enough.

Slates along valleys, ridges, eaves or rakes are always to be secured with at least 3 roofing nails or pins.

In case of double rectangular roofing it is done with 2 roofing nails or pins or with one hook (Swiss clamp).
Nailing is always done under the side lap, except for the last (end) slate which is recommended to be fixed with a copper screw that is at least 40 mm long and has a rubber washer.

When tiling the wall, in the case of the German tiling methods 3, in the case of regular double roofing 2 roofing nails or pins are needed for proper fixation. As for single rectangular roofing, if the slates are bigger than 33x23 cm, then each slate has to be secured with another hook.
These rules are worth following in case of expanded rectangular roofing as well.

In case of nailing to a min. 24 mm thick chipboard at least 3, min. 35 mm thick stainless steel or copper slate screw-nails must be used.

In case of rectangular roofing fixed with hooks the clamps used must be made of stainless steel or copper. This applies to roofing and wall tiling as well.

Splitting
The thickness of the slates to be splitted is between 4 and 6 mm in all methods of roofing, in general 5 mm (dark grey, also known as anthracite).
Regarding coloured slates (green or its shades and red or its shades) it is between 5 and 8 mm.

Overhang
If the ridge, the hip or the rake is covered in a way that it overhangs, then the row facing the dominant direction of the wind must overhang at least 5 cm on the row that is protected from the wind.

Dominant direction of wind
If you want your roof to be rainproof, then in case of roofs with a lower inclination it is recommended that you pay attention to the relation of the panes of the roof (left or right-positioned) and the prevailing direction of the wind. This particularly applies to roofing with curved-end (bogen) slates.

Underlayment with asphalted plates
In case of full-surface sheeting, in accordance with the regulations of the Hungarian or the European Standards, sanded and asphalted plates or glass-laminated plates are recommended as a shield against dust, snow and so on. In case of battening the sheeting has to be supplemented with brandering and roofing foil.
In case of wood-panelling the use of asphalted plates or plastic foil is definitely not recommended since they can aslo function as a vapourtight layer.

Important information

Regarding slate you always have to know where the it was mined!
Slates from different sources must not be mixed; this is what the regulations of this profession rationally specify. Why? Because the roof or facade tiled with slates become strikingly uneven, which then will result in complaints. Slates from different mines have different surface structure and shade.

On a given roof you should always apply slates from the same mine!

Slates are not all alike!
It is immediately explained if you take a look at the formation of the slate. First, the finest clay sediment hardened into clay deposits, then turned into slate through the crumpling of mountains, affected by high pressure and temperature about 400 million years ago.
Good quality slate which is suitable for roofing and wall covering forms only in such areas where just a small amount of pollutants (lime, oxygen, sulphur, ores) is washed into it and there are optimal pressure and temperature conditions.
The slate's typical colour and characteristics are determined by the materials in it. If there is too much iron, lime or carbon in it, then it results in poor quality slate. For instance, black slate contains too much carbon and thus it easily becomes crumbly and mossy. The iron content tints the slate red, yellow, greenish brown, while coal and asphalt colour the slate bluish grey or black. This is why it is important that you should always touch upon the required deposit when ordering, just to make sure about the quality.

According to the three qualities

The structure of the rock
- duration
- colour-fastness
- acid resistance

Treatment
- watertightness
- covering features
- quality control

Roofing technique
- roofing methods
- fixation
- base structure

When ordering, always check the quality and rely on our expertise.