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What is Dry Rot and How to Solve This Problem

Last modified: 2021-05-26 | Approximate reading time 4 mins

Léa Plourde-Archer

Are you familiar with «building cancer », dry rot or serpula lacrymans? More and more stories are coming out in the media about people experiencing terrible situations where this fungus attacks the building materials of their house. In this article, we will try to provide information about this type of bacteria, its causes and potential consequences.

Serpula lacrymans is a type of fungus that typically attacks wood. More specifically, it attacks humid wood and proceeds to decompose it. Any material that contains cellulose is prone to dry rot, which is the most common cause of wood decay in buildings. 

How to identify dry rot in your home

Dry rot appears on the surface of the wood and it looks like thick white cotton wool or like a big cobweb which will turn gray over time. If you notice anything that resembles this description, act quickly. Since dry rot feeds on humidity, the first step is to solve the situations that are causing the proliferation of this fungus, to make sure that it can’t develop more than it already has.

This means that the ventilation around the area should be optimized and that the wood should be protected from any contact with water.  Please note that whether or not you have a problem with dry rot, your house should always be properly ventilated and protected against water ingress. If your house is well maintained, the dry rot will be less likely to spread.

Dry rot in wood

Photo: Wikimedia Commons Majavamm

The dangers of dry rot

Dry rot will destroy the wood’s cellulose, leading to decay, which may cause the material to crumble. Wood that has been painted will start bloating, which will cause paint chipping. Without treatment, dry rot can even end up attacking masonry joints. Once this happens and it starts spreading too much, the only solution left is to destroy the whole building.

One of the biggest dangers of dry rot is probably the fact that it can also spread inside the walls and around electrical wires, which will cause sparks.

Thirdly, note that dry rot can have important health consequences. It can cause respiratory problems such as bronchitis or asthma and lead to sinus or ear infections. When ingested, one should know that dry rot spores are toxic and can cause allergic reactions.

It should also be noted that it is not always possible to detect the presence of dry rot during a pre-purchase inspection. Why is that? Simply because it can literally grow under the insulation (including urethane) and therefore not be detected. Moreover, the moisture contained in this type of insulation is favourable to the growth and proliferation of dry rot.

How to treat dry rot

If the dry rot keeps proliferating after you’ve solved the issues that were causing it, the best remaining option is to opt for is a fungicide treatment program. This treatment contains three steps. First of all, the wood must be stripped in order to be fully bare. This step serves to remove the wood that has been infected and is therefore already dead, to leave only wood that can still be saved.

Masonry joints will also be treated with a similar technique, meaning that the joints that have been attacked by dry rot will have to be cleared out and replaced. Before the new grout is applied, the bricks must be disinfected using a flame torch.

During these treatments, which can last months, the building occupants will have to move out. Depending on the amount of contamination, several wooden structures might have to be destroyed and replaced.

Unfortunately, dry rot diagnostics rarely come at an early stage. In many cases, it’s already too late to save the building, meaning that the only solution left is to destroy the whole structure and rebuild it from scratch. That’s why it’s so important that you regularly inspect the current state of the wooden structures in your house, so you can avoid facing such an extreme situation. 

Tips to avoid the transportation of dry rot spores

Although it may be difficult to avoid transporting dry rot spores, it is important to proceed with caution and to avoid bringing large quantities of firewood inside the house. When you have to do it, be sure the wood remains dry at all times.

Also, be aware that a contaminated home will become uninhabitable. Although it is particularly expensive to replace all furniture when moving, note that the risk of contaminating your new home with spores embedded in the furniture is high. Therefore, it will be best to leave them behind, despite the frustration and sadness caused by this situation.

Government efforts to help those affected by dry rot

In Quebec, a government program was created by the Liberal government of Philippe Couillard in the late summer of 2018. This program, known as the Programme d'intervention résidentielle- mérule pleureuse, includes a pilot project scheduled to begin in the month of October of the same year. This program provides $5 million over three years for affected residential building owners.

This program will also serve to "continue the development of knowledge on dry rot and expertise for its identification", to "specify the number of confirmed cases of dry rot" as well as ''to determine the best approach to reduce contamination in Quebec''.

Eligible owners will be able to get up to $ 150,000 in financial assistance. However, this financial assistance is granted only under certain conditions, the main one of which is to rebuild in the same place within one year.

Source: Société d'Habitation du Québec

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