What Mould Does To Buildings & How Mould Can Damage Your Home & Health

Building Effects

Mould doesn’t just affect your health; it can also damage your home. A large number of mould species have been shaped by evolution to break down cellulose, hemicellulose, and lignin (all components of wood). Given that many homes and businesses are mostly built out of wood, this can be a big problem if a water leak occurs. Dry rot can occur as well, but it is far slower to do damage and still needs a source of water to begin growing.

The damage done by mould tends to occur over a long period of time, even when the wood is very wet. In fact, most of the time, the water does more damage over a short period of time. However, the wetter and warmer the wood, the faster it will breakdown. Some fungi and bacteria produce an enzyme called cellulase which acts by breaking the bonds in the cellulose, lignin, and hemicellulose molecules. Thus, the more the fungi is allowed to grow, the more cellulase will be produced and the faster the wood will break down. Others produce hydrogen peroxide to do the same job.

Is there a way to repair the damage done? Yes, and no. When the fungi begins growing, it’s already doing damage, but if caught early, the damage is minimal and can be repaired (even as simple as painting over it) easily. If the damage is more extensive, total replacement of the materials may be required. This may mean a simple cut and replace of drywall, but if the moisture problem has been going on for some time, structural members may need removal and replacement.

In other words, building materials can be attacked by mould, but it is possible to save them and repair the damage done. It comes down to how fast the moisture is found and dealt with. If the moisture is found quickly, the damage will be minimal. It is rare that so much structural damage is done that the building has be torn down, but it can happen. Dry rot has destroyed many older buildings, but even if the damage is extensive, some repair can be attempted.

Dry rot is caused, to a large extent, by a fungi called Serpula lacrymans, but can be caused by a few other species. It has a major economic effect as it is considered the most damaging destroyer of wood construction in temperate zones.

Soft rot occurs when fungi like Chaetomium sp. infect wood and begin to break it down. These are a cellulase excreting fungi and often need a source of nitrogen to synthesize the enzyme.

White rot fungi digest the lignin in the wood, but can also break down cellulose. These fungi are common throughout the natural world and have been co-opted into industrial processes.