Rotten Wood, Carpentry, Ventilation

Not Enough Air = Rotten Wood

We often replace roofing (membranes) and see that there is rotten wood. Of course, water infiltration can cause that kind of damage, but it’s often a lack of air that damaged the (wooden) decking.


In certain cases, there could be signs, especially in cold weather between December and March. Orange or brownish spots may appear on the ceiling where drops of water show up when it’s cold out but not raining.


We usually encounter two situations that can cause this problem: In photograph # 1, the attic had TOO MUCH insulation. The air was cut off, contributing to the rotting wood conditions over large areas and in several different locations.

We can see how the wood, and even the joist, got black and damp, and the boards are seriously damaged due to the lack of air circulation, because all of the joists are going in the same direction. Therefore, air cannot circulate uniformly through the attic, and the air is caught between the joists and can never be properly evacuated, which can cause serious rotting, fungus or other problems.


Unfortunately, there are not many good solutions for solving this problem. The best one would be that your roofing contractor manufacture an air space where air can circulate easily and uniformly (in all directions) in the attic, as we did for our client in photograph # 3.

If you have any suggestions or comments, contact us!

Jacques Perron
Published October 28, 2013

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