It does "sometimes happen. The roof of a construction project is being waterproofed. About the cladding, the builder would like to think more thoroughly. "No problem, I hear it!", says the roofer. Weeks, even months pass. Not a cloud in the sky: until someone notices: all the cavity panels have become rotten and delaminated 😱. Sound familiar? You're not alone, as this case proves. How you can easily prevent this, read below.
In this case, a choice was made for a wood type with a low durability class and a non-humidity resistant bonding. The humid conditions caused the layers to separate from each other, and the wood began to rot.
A plywood or concrete plywood for damp conditions ideally has these specifications:
Crepi is almost always installed AFTER the roofing work has been done. The roofer comes to waterproof the roof at a time when there is no cladding, and therefore no protection for the roof structure.
The situation is then as follows: the entire roof package is installed, with the exception of the eaves, which will only be installed once the facade package is fully in place.
Therefore, the plywood that serves as the overhang of the cavity remains additionally exposed to damp conditions for an extended period of time.
For a plywood with the right durability class, this is basically not a problem, but that's where the shoe pinches in many cases. Without often realizing it properly, plywood is installed for indoor use, with all the consequences....
In a gable brick situation, you won't see this very easily. This is because the masonry is usually there BEFORE the flat roof is installed. So the eaves will not be exposed to rain and moisture to that extent.
Still, we give the same advice here: for humid conditions, always choose the construction site with appropriate specifications.
In this case, the plywood had to wait 6 months for a facade finish. Not a problem if you use the right panel, obviously a problem with unsuitable panels. So the panels were rotten and delaminated.
The result? All roof edge seals had to be reopened and new plywood installed. The cost was shared between the builder and the roofing contractor.
This case shows that it is essential for roofers to choose a plywood with warranty. Then, as a craftsman, you can be sure of consistent composition. Still a rotten panel somewhere, or a case of delamination? Enjoy your conclusive warranty and don't pay the bill yourself.
