chip board under felt roof

[chezbank]

We have recently had a shed built which has a torched on felt roof on top of chipboard. After the first very wet spell we found that the chip board started to develop widespread black areas, supposedly damp. There is no evidence of water getting in and the felt roof looks sound. Could it possibly be air moisture? Any ideas? :

 

[big-all]

did the compressed wheetabix get at all wet before being covered!!!

 

[datarebal]

I have seen this a couple of times once on ply, due to damp air and in the ply case which was a stable block caused by steam from hot horses and the other was a tropical fish house

 

[noseall]

the mould cold be a product of of condensation.

do you happen to have any petrol driven machinery stowed away in this shed?

is the shed heated?!

 

[^woody^]

It's condensation due to the cold external surface, and mould feeding off the glue/timber starch.

Either insulate to raise the surface temperature, or paint/seal the bare boards to remove the mould food source

 

[joe-90]

If this only happened after the first wet spell rather than during the frosty spell I wouldn't bank on it being condensation.

 

[Deluks]

Is black mould a problem? I've a few plywood board with some small patches of black mould, and a few areas that are 'spotted' They're back in the dry now so should I give them a coat of timber preserver and reuse or are they now firewood? It's only on the surface, the cross section ply beneath seem fine when cut. These will eventually be used to reroof my garage.

 

[^woody^]

The mould is living on the surface of the board and not eating it as such. It can be brushed off and if the boards treated and used.