Four Common Causes of Damp Walls and How to Fix Them


Buying a converted barn that needed a LOT of work has been an education. When we viewed the house, it had been empty for over two years. We did all the surveys, there was no sign of dampness; the house was way dry, but the water had been turned off the whole time the barn was empty. It wasn’t until we had lived in the house for six months that the cracks started to appear. Now, 15 leaks and floods later, we have had a varied experience of how to deal with a multitude of leaks and damp situations.

We found a combination of wet weather, poor flashings, and a lack of basic home maintenance skills, coupled with the house being empty for so long, worsened the problem. But there can also be a number of reasons why walls become damp, so let’s look at some of the most common causes and how you can fix the problem.

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Barn Renovation Tips

Rising Damp

Rising damp can be a serious problem for homeowners. If wet patches appear at the bottom of your ground-floor walls, it could be rising damp. As the name suggests, this is when moisture seeps into the walls from the ground up. 

There are a few reasons why it happens, but the most obvious is the lack of a damp-proof course. This is common in old barns and period homes; we were fortunate our barn did have a damp-proof course. But rising damp can also occur when a damp-proof course has failed or been disrupted. This can be the case when a new path, patio or yard has been laid higher than the house’s damp-proof course. Also, check for broken drains, and they can cause issues.

Treating rising damp typically involves having the walls injected with damp-proofing material to stop the moisture making its way up your walls. But you may also need to lower your exterior landscaping back below the original damp-proof course level. Any damaged plaster, skirting and flooring will need to be fixed, too. However, a damp-proof specialist and a general builder should be able to advise you on the best solution and undertake this work for you. 

Penetrating Damp

Penetrating damp is the term for any moisture that manages to get through your walls from the outside. In a well-maintained home, this shouldn’t happen. But over time, mortar or flashing can crumble away from brickwork, and gutters can become blocked or broken so that rainwater can find its way through your walls.

For us, it was easy to diagnose and fix the penetrating damp. As every time it rained our stone bathroom wall became damp as the water seeped through the stone as rose up the wall.

It was a mystery for a while until we discovered the flashing on the bathroom roof was damaged. It was just a case of clearing and repairing guttering, re-doing the flashings and repointing brickwork.

You can do this yourself or hire a handyman or builder to help deal with the issue; I can’t tell you the relief we felt once the problem was resolved. If in doubt, please call a builder in to check the problem. We are lucky to have a great team of builders to call on in emergencies.

Poor Ventilation

A lack of ventilation inside your home can actually cause damp on your walls. This can be a problem in well-insulated homes or with high moisture levels. 

In modern homes that are very well insulated, you need a good ventilation system to allow fresh air in and enable it to circulate properly. If you don’t, the air and the moisture becomes trapped inside your home. This can lead to the walls becoming damp and mouldy. 

Equally, in homes with excess moisture from kitchens, bathrooms and drying laundry can suffer from damp walls unless there’s adequate ventilation and air circulation. 

When poor ventilation is the cause, you’ll often find the exterior walls and corners of the room become damp, and you may find black spots appearing on the surface.

There are some easy fixes to this damp problem. Opening the windows is often the easiest solution. Modern windows come with trickle vents fitted, allowing air to circulate without you needing to open them. So, you may want to consider upgrading your glazing as we did. If you’re drying clothes inside the house, keep fresh air circulating and consider using a dehumidifier. 

Tips for renovating a barn kitchen

Hidden Leaks

Our home is structurally sound and well-ventilated; despite this, we still managed to find wet patches on the walls. We found hidden leaks as we started renovations on our new barn kitchen in the old kitchen and bathroom, many in fact.

The main leak which caused the most damage came from the old copper pipework that ran inside the old kitchen walls and between your floors. It became clear there was an issue when we started to notice a damp smell. Fortunately, we were able to trace the pipes and find the leak. However, because the pipes were in the wall the wall had to be chaneled out, which revealed a lot of rotting plaster.

Although there is no way of knowing if you have leaks in internal walls, telltale signs include damp smells and excessive condensation.

If a leak is quite bad like ours and your wall is wet, turn your water supply off via the stop tap. This is usually found underneath your kitchen sink, but do make sure you familiarise yourself with the location of the stop tap; ours is in the adjacent field to the barn; crazy, I know! Only once the water is turned off, should you call out an emergency plumber.

Old Houses Bring Issues

Despite all the issues, we don’t regret buying our country barn. We knew it would have secrets and, thankfully, are working through and replacing pipework, flashings and guttering. If I could give you any advice, it would be have a great team of workmen to call on. Go for stone floors; leaks can’t damage the stone. It is hard-wearing, and despite the drama, try not to let it stress you out.

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