The Dangers of A Damp Underfloor

Last Updated on April 20, 2022 by Kravelv

A damp underfloor should be taken seriously as it can lead to a number of issues. The sooner it is resolved the better.

How You Get A Damp Underfloor

There are several ways in which your underfloor can become damp. The first is that you have a leak that has gone unnoticed and is making its way to the lowest point in your home. The longer this is left the damper the floor will get. The key to noticing this type of damp is that that the stain will be in one area of the floor and head outward.

Of course, a leak can also refer to rainwater getting in through cracks in your home.

Fixing the leak and drying out the underfloor area will resolve the issue.

A second way that damp can build up is when you have inadequate ventilation under the floor. This allows humid air to build up because the space gets warm and the moisture in this warm air comes into contact with your underfloor. The longer the bad ventilation continues the bigger the damp problem.

The only way to resolve a lack of ventilation is to add subfloor ventilation. The flow of air under a floor is essential to ensure that warm air is moved out and cool air allowed in.

It’s also worth noting that damp can be caused by a failure of the damp-proof cause. This may because it is old or because it never existed. The damp-proof course prevents damp from coming up through the floor and into your walls and floor. This is known as rising damp. If the damp-proof floor has failed you’ll need to replace it, you may even need to have a chemical injected in your walls to create a damp-proof layer.

The Dangers

Knowing why your underfloor is getting damp is important as this will allow you to fix the issue. But, don’t be tempted to put the matter off. There are serious issues connected with damp underfloors.


One of the biggest issues is that damp warm spaces attract bacteria that cause mold. These multiple quickly and the mold spores will float around your home. Unfortunately, mold can be a serious issue for your health, especially if you already have allergies.

Structural Issues

Damp on your underfloor will cause wet rot over time. In effect, the wood in your home will disintegrate. If you step on a rotten piece you may go straight through the floor. This can become an expensive issue and cause serious injury.

However, that’s not the only structural issue. If you have a damp subfloor space the damp will start to penetrate the foundations of your home. Over time the foundations will weaken, ultimately resulting in movement.

This movement may initially be slight and show like cracks in your walls. But, if left, it can actually cause part of your house to sink and potentially destroy a section.

One thing is certain if you suspect damp in a room investigate it straight away, leaving it will make the issue worse.