Mold treatment for a cathedral ceiling and roof sheathing?
I’m trying to find the best way to treat mold that developed in the boards of my cathedral ceiling as the result of a roof leak. I’m going to have the roof replaced (which will solve the leak problem and remove moldy insulation), but I still need to treat the wood that will remain on the ceiling. None of the mold treatment companies I contacted are willing to work on a roof. My contractor suggested I ask here to see if anyone knows the right way to address this problem.
Here’s a fuller description and a photo:
Last summer my roof sprung a leak when the flashing along the chimney came loose. The leak started gradually and I did not notice it until the insulation and boards below became soaked and water started to drip into the living space of the house. The house has a cathedral ceiling made of exposed wooden boards. The insulation (a single sheet of foil-covered foam board) sits on top of those boards. The roof itself is asphalt shingles.
While the leak has been plugged and I have a roof replacement scheduled, the wooden ceiling boards are still a problem. Every time there is humidity, the affected area develops a terrible moldy smell.
What is the best way to treat these boards? Is there something effective we should saturate them with while the roof is off? Does anyone know a mold remediation company in southern Vermont that could do this work? One mold company recommended I apply a product called Benefect. Since the treatment needs to be done while the roof is off (and the mold is a health issue for our household), I want to make sure to figure out the most effective course of action.
In the worst case scenario, we could replace the ceiling boards. But, the new boards would stand out against the aged wood of the rest of the ceiling and this would negatively affect the aesthetics of the house.
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Replies
It sounds like you’re getting a new roof. I’m going to assume the roofers are going to replace the likely water damaged sheathing and insulation as part of that work so you won’t have to deal with mold remediation of those parts of the assembly.
You likely have mold issues on at least some framing and the ceiling boards that you can visibly see. The mold will grow where the water went, and also where the water made it humid enough for the mold to survive. This often means the mold will spread in roof/rafter cavities for quite a distance from where the actual leak is. In my own house, a small leak (and some issues with ceiling air sealing that wasn’t done by the previous owners), the entire interior part of the ceiling assembly was black with mold. The remiadiation company sandblasted everything as a first step, then sprayed. Make sure to inspect everything while the roof is off to ensure you don’t miss anything.
If you have only a small amount of visible damage, you can probably treat it yourself but the usual disinfectant solutions use will bleach the wood. There are commerical mold disinfectant solutions, but for small amounts it’s common to use either a bleach solution or hydrogen peroxide. Hydrogen peroxide is easier to work with and less persistent, but it also is less likely to completely kill all of the mold. Both bleach and hydrogen peroxide are going to permanently alter the appearance of the wood. If you want to try this, there are tutuorials online. Be sure to wear eye protection (goggles) and a respirator while you work.
You may have mold on the “other” side of those appearance boards where you can’t see it. You need to treat those areas too, if there are any. Basically you need to be certain you don’t miss any moldy areas since if you do, the moldy smell will persist.
The mold remediation pros will recommend encapsulating the treated areas when you’re done too, to help ensure the mold doesn’t grow again in the future. In my project, the spread foam I was installing took care of that. You can also do it with mold-killing primers.
unfortunately , if you have mold on the visible sides of those boards, you’re probably not going to be able to completely preserve their appearance.
Bill
Hi Bill,
Belated thanks for this thoughtful reply. I agree with you that we have to treat all the affected areas so that the moldy smell does not persist. Part of the challenge is that the mold we have (at least on the visible side of the ceiling) is not black mold, so we can't necessarily track it by eye. Of course, as my mold inspector made clear, that doesn't mean the wood isn't permeated with mold growth. From your answer, it sounds like there's a lot we can do on the top side (that will be under the roof), but it's much trickier to deal with the indoor surface. Perhaps it makes sense to get a solid plan for the top surface, so that my roof replacement can go forward, and then deal with the indoor surface as a separate project. So far the only professional advice I've received that isn't directed at black mold is to spray with a product called Benefect. The mold remediation company that treated a leak in my basement used this product.
Do you recall what your mold remediation company sprayed with? Also, where is that company based? I've not been able to find a mold remediation company that will go up on a roof, so I would be interested to contact the company you used.
Thanks so much for sharing your thoughts on all of this,
Kristin
Hi Kristin -
Martin Holladay wrote a great article on mold on GBA: Common Sense on Mold : https://www.greenbuildingadvisor.com/article/common-sense-mold.
Peter