Lateral Damp Penetration Explained

Lateral penetrating damp is a very specific problem in the home, and it is easily misdiagnosed. It’s a problem that you’ll experience in the lower floors of the home. But, it’s particularly prevalent in homes with a cellar or basement. Why? Because lateral penetrating damp appears when the ground level is higher than the damp proof course. That means water damage is getting into the walls below the current level of protection. If you’re looking to convert a basement into a useable room, you’ll need to protect against this.

It tends to appear on homes built on sloping ground, and attacks basements in particular. As you can imagine, cellars are sunk deep into the ground, and the damp will penetrate those structural walls. It’s not to be confused with ‘normal penetrating damp’, or rising damp. As such, it requires a very different, and very specific, solution. First, let’s learn a bit more about how to distinguish it from other forms of damp.

How is lateral penetrating damp different from other damp?

We’ve explained how lateral penetrating damp enters the wall below the damp proof course. It attacks the lower levels laterally, ie from the side. It could be a result of wet soil resting against the wall which is typical of basements and cellars. It could also be the result of wet decking adjoining the wall joint or rubble left against the exterior.

This is different to rising damp, which is drawn upwards (not laterally) through the wall, by capillary action. This is stopped using a damp-proof course, but, it won’t stop lateral penetrating damp coming in sideways from below.

How to spot lateral penetrating damp

So, how exactly will you know if you’ve got lateral penetrating damp? The first sign is usually a discoloration and the feeling of damp on the lower walls. In more extreme cases, you’ll see a clear tide mark on the plaster. If you have a cellar or basement, check it regularly for these symptoms. Secondly, you’ll notice wet or rotting skirting boards along the floor line. A damp meter will then measure the extent of the total problem. The wall will also feel cold to the touch, and mould may start to appear as a result of condensation.

How to prevent and treat lateral penetrating damp

It’s important that you take a different approach to rising damp or normal penetrating damp. This problem needs a bespoke approach using a Structural Water Proofing (tanking) system. We will have to strip the plaster back to the bare wall, then install the tanking system. We use coats of a cementitious slurry and bonding agent to waterproof the wall. If you’re looking to damp-proof a basement or just one wall, the system is perfect.