Corrosion resistance mechanical fasteners when used on pool roofs
There is a lot of uncertainty about the mechanical fastening of roofs on swimming pools.
This is partly because there are different rules and customs in the different countries around us. Mechanical fasteners on roofs of swimming pools are simply not allowed in Belgium. As a result, roof systems on roofs of swimming pools are always glued in Belgium. In Germany and the United Kingdom, for example, only stainless steel fasteners of at least A 5 quality may be used.
Investigations into fastening systems
In recent years, various studies have been conducted in the Netherlands into stainless steel fastening systems in a swimming pool environment. These investigations mainly focused on stainless steel suspension systems of, for example, pipes and installations.
For use on swimming pools roofs, austenitic stainless steel has been shown to be sensitive to stress corrosion in chlorine-rich environments. Especially on the underside of the roof where the stainless steel screws are exposed to the chlorine. In addition to stress corrosion, the phenomenon is known that the steel profiles can corrode around a stainless steel fastener, causing play between the fastener and the steel and the screw to become loose, so-called steel corrosion.
Advice!
Due to the results of these studies, Guardian recommends that carbon steel screws be used on roofs of swimming pools, with a coating that provides corrosion protection of 30 cycles according to the Kesternich test.
According to the European Assessment Document (EAD), a standard roof screw must have a minimum corrosion resistance of 15 cycles according to the Kesternichtest.
Guardian screw on steel decks: BS 6.1
Guardian's BS-61 screw has a so-called 30-cycle coating. The coating on our BS-61 screw will not show the above-mentioned forms of corrosion. The carbon steel prevents stress corrosion, while the coating steel prevents corrosion.
We therefore recommend the use of the Guardian BS-6.1 screw, with the 30-cycle coating, preferably in combination with a tube system, for fastening a roof system on a swimming pool.
A screw/tube combination reduces the fastener's thermal bridge through the insulation. This also gives you less condensation on the screw.
Other roof types
There are no problems with mechanical fastening on concrete and light weight concrete roofs. This is because the fastener is in the surface and not in contact with the indoor climate. You don't often find a wooden substrate in a swimming pool. Advice on this is always on request because the types of wood are diverse and the best solution has to be determined on a case-by-case basis.