How to deal with dry rot

Serpula lacrymans, or dry rot as it is more commonly known, is unsightly, unhealthy, and can seriously damage your home’s structural integrity.

Home maintenance

20 March 2018

Perfectly good joists, wood beams, and floorboards can become nothing but a crumbling mess once they’re infected by dry rot, and, as the spores spread quickly, it won’t take long before all the structural timber in your home comes under attack. In fact, a single case of dry rot can cost anywhere between £1,000 and £2,000 to remove, and thousands of pounds more in building repairs.

Spotting dry rot before it takes hold is half the battle - if caught early enough, you can save a fortune in repairs and take action to prevent it coming back for good. The fungus that causes dry rot in wood prefers warm, damp, dark and unventilated places to grow. While it’s usually associated with old properties that are being renovated, it can also appear in modern homes, too. Don’t rule dry rot out just because your property is newly built; if you notice any symptoms of rot in your home’s timber, it’s important to identify it and embark on a course of dry rot treatment to eliminate it immediately.

Find out what causes dry rot, how to identify it and get it treated quickly, and, most importantly, how to deal with dry rot in the long-term.

What causes dry rot and how to identify it

Dry rot is caused by species of fungi that initially attacks wood. If it’s left unchecked, it can quickly move onto masonry and plaster, impacting the structural integrity of your home which can cause long-term problems.

Despite its name, dry rot only affects damp timber and structural materials. This can be caused by high levels of condensation in your home. Water entering your home from an external source, for example as rising damp, also causes dry rot. A leaking washing machine sitting above floorboards that haven't been treated could also be a culprit. Before attempting to tackle the problem and starting a course of dry rot treatment, it’s important to make sure that you’re dealing with dry rot, and not a form of wet rot.

One major sign to look out for is shrinkage. If dry rot is the culprit, the wood will shrink and crack, usually in a rectangular pattern. If the air in your home isn’t overly humid, the fungus will appear as a grey skin with yellow and lilac patches. If it is humid, the fungus will appear fluffy, like cotton wool. There will also be fruiting bodies (mushrooms), which can range in size and look like flat, fleshy pancakes. These are brown to orange in colour, and are where the spores come from. Fruiting bodies of less than a metre in size can produce over 50 million spores per minute for days on end. The spores then spread to other damp timber in your home, or to your structural masonry, and the infection grows.

How do I get rid of dry rot?

Getting rid of the infected materials is the first step in your dry rot treatment programme. You will need to contact a professional. Depending on the extent of your dry rot problem, you might need to remove a lot of structural timber from your home, so it’s best to have an expert on hand. If you’re not sure what you’re doing, you might damage the structural integrity of your property even further.

Any wood that has been infected by the fungus has to be removed and replaced. It is recommended that you also remove healthy wood from a metre surrounding the site of the original infection, and the new timber needs to be treated with a fungicide. 

It’s also a good idea to treat other structural timber in your home to prevent future infestations. The dry rot treatment will stop the mould spores from settling in again, even if the wood does accidentally get damp in the future.

If the dry rot problem has spread from the wood to the structural masonry, you will need to remove this too. The dry rot spreads by mycelium, which are like thin tentacles that spread through the damp materials. Once you’ve removed the affected plaster and mortar, keep removing until you've cleared a distance of one metre from the last mycelium.

Once you’ve repaired the damaged areas it’s important to make sure the room is well ventilated, as this will help to dry out the damp patches. Make sure the curtains are open during the day: dry rot likes warm, dark, and damp places, so plenty of natural light will also hinder its progress. You should also invest in a dehumidifier and put it in the room that was affected by the dry rot. This will keep air moisture levels at an acceptable level, and prevent the need for further rounds of dry rot treatment.

Preventing dry rot in the long term

Dealing with the cause of damp in your property is the best way to stop the fungus from coming back. Dry rot only takes root in surfaces with a moisture content of 20% or higher. If this drops, the dry rot spores will become dormant. First you need to find the source of the damp. The most common is condensation, which affects a fifth of British homes during the winter months. If condensation is the culprit you will need to reduce the humidity levels in your home; always use an extractor fan, and heat every room evenly.

The rarest form of damp is rising damp, which can also cause dry rot. Homes built after 1875 have damp-proof courses, which should stop rising damp from occurring, although in some older properties the course can become damaged or breached. Rising damp appears along the bottom of your walls, usually just above the skirting board. It can rise up to one metre, so there might be tide marks left behind and a salty residue on the plaster. If your dry rot problem is being caused by rising damp you will need to seek professional help to discuss an appropriate course of dry rot treatment. 

Cracked pipes within your internal walls, a breach in your home’s fascia that lets rain water in, broken guttering, or a faulty appliance like a washing machine can also cause problems with damp, which can in turn lead to dry rot. Check your property thoroughly for any leaks or breaches. If your washing machine or dishwasher often leaks, consider replacing it. Make sure you clean your gutters at least once a year to stop them from overflowing or breaking. The key is to stop water from seeping into your property, preventing it from creating a welcome environment for dry rot.

Helping you do more of what matters

Your time counts. We get it. That's why we've made it quick and easy to make your AXA home insurance claim online. It only takes about 20 minutes to do2 and we’ll get in touch the next working day to talk about what happens next.