Dry rot is a bane for any roofer, carpenter, or anyone who works on homes. Dry rot will desiccate wood, leaving it crumbling into cubes and then turning it into a fine powder. When in a roof, dry rot can become a serious structural problem that destroys wood and causes roof collapse. So, what causes dry rot, and what should you do about it?
Fungi Cause Dry Rot
Dry rot is caused by a few different species of fungi, including Serpulalacrymans and Meruliporiaincrassata. While most fungi require humid conditions to grow, the fungi that cause dry rot need comparatively little. Most can start growing on timber in conditions as low as 28% humidity, and after this, will keep growing in the wood even if it dries out to as low as 20%.
Dry rot first got its name on shipyards, where boats that seemed fine would begin to crumble when they were dried out. The wood on the boats was already infected by the fungi when wet and simply continued deteriorating when dry. Once it was understood that a fungus was causing this rotting process, biologists theorized that the fungi in question produced its own moisture through translocation. The fungi can do this, moving water to itself from up to 30 feet away, but we’re not sure if it is increasing the moisture content in the wood by translocating water. It is now thought that the fungi just does well in low moisture environments and isn’t too busy about providing itself additional water.
Other Wood Rot
The fungi which can digest the cellulose in wood are called xylophagous fungus. These species can cause other kinds of rot, such as brown rot, soft rot and white rot. Each requires some level of moisture to begin, prefers different pH, and creates different fruits or spores. It’s important not to assume that the fungi growth you see in your roof is dry rot. Instead, have a professional assess the wood and determine what needs to be done in order to protect it from more fungi growth.
How to Handle Dry Rot?
Once the fungi that causes dry rot is established, it is very challenging to treat the wood. It is unlikely you would be able to reduce moisture conditions in your roof enough to stall the growth of the fungi. And, if the characteristic orange dust has begun, this is the spores of the fungi and it is very likely to spread.
Instead of trying to treat true dry rot, the best thing to do is to cut out all of the infected wood. Epoxy treatments are a common option, but they may not work and when the wood is in your roof, it is absolutely essential that you not leave the condition of the wood to chance, or you risk collapse. Not only may you need to remove wood, but it is sometimes necessary to clean up any limestone walls near the rot, as they can allow for the rot to spread.