Brickwork below DPC causing internal dampness

20 Sep 2015
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United Kingdom
Hello. Recent heavy rain has highlighted a problem in my house that I moved into 6 months ago. Brickwork below DPC did have tinges of green when I viewed the house but I put this down to a spell of heavy rain that the sunshine would fix. Recent heavy rain leads to pools of water that does not get above DPC level but does keep the below DPC level brickwork wet for days. Double height air bricks also seem to be compounding the issue as the water does seem to be getting into the property via this route. I spoke with a local DIYer who said this was nothing to worry about as the water would drop into the cavity gap and eventually evaporate from there. In the meantime, if the cavity gap filled up, the water would then go under the suspended wooden floor but still only pool around the brick mini walls that support the under floor beams. However, there is dampness in the floor level cupboards which are fitted against the corner walls where, outside, the rain pools and the brickwork looks like the pointing has deteriorated and the bricks are looking decidedly pitted. I guess that the systemic fix would be to resolve the pooling of rain water outside. However, this may involve significant underground work to add drainage. My immediate need is to stop the ingress of water through the brickwork and through the airbricks to give the cupboards a chance to dry out so that I can use them. I have thought about removing the double brick height airbricks and fitting single height ones above a full brick so removing the airbrick holes at ground level which easily allow water to flow in. But I am not sure of the implications of such a change. Is it feasible to replace the 2 courses of bricks below DPC, gradually, and seal them ? I can DIY to a standard but am no professional builder. Your professional advice would be most welcome.
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As you have already concluded, the solution is to keep the water away from the walls/subfloor in the first place. French drain sounds favourite, doesn't have to involve significant underground work. Leave the airbricks alone UNLESS you have a massive excess of ventilation to the subfloor. And replacing the bricks below DPC sounds like very hard work. Next time it is pouring down, have a look at the outside of the house & make sure rainwater isn't missing the guttering and pouring down the wall (quite common at corners). And while you're at it, check that the rainwater coming from the gutters is actually going somewhere.
How would I know if I had a massive excess of ventilation to the sub floor ? The internal dampness is to the plywood lining of the cupboards. It goes green and mouldy and I sometimes even see small amounts of water on the floor of the cupboard (1 or 2 teaspoons worth). I would have to take them out altogether to be able to check the actual wall and the wooden floor. I will be doing this when the weather improves but I want to be prepared for what the best thing is to do before I get to the point of ripping cupboards out and carpets up. BTW, Happy New Year to you both :)
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Your first step must be to prevent water pooling round the house. Is it concrete paving that does not have a slope away? Is the ground around the house sloping towards it?

Forget about internal work or the airbricks until you have rectified the source of water.
Mould is a symptom of condensation. If you see water on the inside, then that's not soaking through from the structure but condensing from the inside too.
John D, thanks for your reply. There are 3x2 flags all around the house which could be lifted and the ground sculpted to have the water run in a different direction. Ultimately, however, the water is not being taken away by the surface drains as they are often full when there is heavy rain. Neighbours have informed me that the land in this area does get saturated easily and some of them have had the expense of having additional drainage installed to remedy the problem. I may end up having to suffer some expense of this nature myself if I cannot find a way that I can remedy the issue. This is why I am asking the questions on this forum. I would like to minimise any cost. My more immediate concern, however, is the internal dampness and the ingress of water via the brickwork and/or the airbricks.
Winter has already dumped a lot of water over the UK, and the first week of January will apparently continue the theme. Any outside work to remedy wetness will probably have no effect whatsoever until warmer temperatures prevail towards the middle of spring. If DPCs keep the brickwork above dryer than the bricks below, then they are doing their work. Bricks are porous in many cases - they get wet and they dry out.

Don't imagine that water is filling up your subfloor spaces - if you are concerned, make inspections to confirm or dispel your doubts. Inexpensive waterproof snake inspection camera endoscope (Google search string) tools are available to hook up to mobile devices like laptops, to look under floors through small holes drilled or already present in the structure of your house. Low-tech solutions like lifting floorboards may also be used to see and feel if the underfloor is wet.

If you have wetness in underfloor spaces, then it is necessary to find the source of the ingress, and plan work to solve this problem.

Indoors, you can ameliorate the condensation threat with air movement - ventilation - using unheated fans to prevent cold air pooling in "dead spaces" like corners, cupboards, and behind cabinets and furniture.

"Ventilation" by opening windows and doors during damp and colder weather allows heat to escape for very little benefit to the internal air conditions. Similarly, dehumidifiers will not help condensation on damp surfaces unless air is circulation over those surfaces.

The more you recirculate air around your home, the warmer the surfaces which would attract condensation will become, and the less likely for moisture to condense there.

You should not increase the temperature output of your heating, but your central heating will work harder to maintain the same ambient temperature due to the flattening of temperature gradients that the recirculation causes.

Any condensation is likely to cause mould, if the surfaces are not regularly cleaned. this can happen on windows, skirtings, walls and within cupboards, and behind furniture. You can buy proprietary antifungals, or just use bleach.

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