Another damp thread

[Coronawireless]

Hi there. We have an 1820s house with basement in a moat. Moved in 5 years ago after extensive renovation. The basement was very damp and builders took up floors and damp proofed underneath. All was well until this year - except that we’ve had a lot of wood lice coming in to the basement and also a pair of boots left in the hall kept going mouldy. In the past few weeks I have been noticing wet patches on the tiled basement floor. Just in certain spots, not all. Actual small puddles of water, almost as though water has dropped from above. We haven’t had a lot of rain and our drain isn’t blocked. Basement bathroom rarely used and kitchen is upstairs. The only thing that’s changed in is that I put salt around the edges of the wall near the door to outside in order to try to stop the woodlice invasion. And indeed they have stopped coming in! But now there is water instead??
Any suggestions before I get a builder in who will rip up the floor and charge me many thousands.

have a look at the area (moat)

it probably has some kind of rainwater drainage.

is its floor higher or lower than the floor in your basement?

does the drainage appear to work? You can try running a hose into it.

After 200 years it may well be cracked or blocked. If cracked, the water will run away into the ground and may cause the paving to crack or sink.

BTW salt will absorb moisture ftom the air. Wipe it up.

Catch some of the water in a perfectly clean bottle and shake it. Drain water contains soap and detergent and will bubble. Ground water may contain sediment.

Woodlice eat the fungus on wet, decaying wood. So you have both damp and rot. Sorry. Are the floors concrete or wood?

Do you know what method of "damp proofing" was used?

If you have a water meter, please take a photo of it. Some have a glass window with an air bubble that turns whenever water is flowing, which will identify a leak.

Good tips thanks.
The main house drain outside seems to be working well. The basement is below moat level. The moat has a working rainwater drain and doesn’t collect water, however there is a high water table underground and the moat is north facing with lots of moss…generally damp …hence all the woodlice about. They die once inside the house so what we find is lots of dead bodies. We didn’t notice actual water inside until laying the salt….probably just a coincidence.
I think what the builders did was to lay plastic sheeting under the floor and up the dudes of the interior basement walls to keep out general damp from the moat.

Up the sides

The water gathering on the floor appears to be perfectly clean and does not smell.

@Coronawireless

The water gathering on the floor appears to be perfectly clean and does not smell.

then it might be clean tapwater.

not exactly good news, but if there is a leak it can be repaired or a replacementpiece of pipe fitted

is the incoming water pipe visible?

I meant to ask

do you know if the builders included a drainage sump under the floor, either connected to a drain, or having an electric pump to empty it when full?

You should have had it tanked. Look into that.

@PigletJohn

I meant to ask

do you know if the builders included a drainage sump under the floor, either connected to a drain, or having an electric pump to empty it when full?

I don’t know but if there’s seepage from a high water table (as I suspect) then we do need this. Hopefully it could be sited somewhere outside the house so we don’t have to rip up the floors??🤞 Someone’s coming to take a look and liaise with our previous builder. Thanks for the input.

As in hopefully a pump could be sited outside the house to lower the water content under the area.

I haven't had one, but a former neighbour (on a gentle hill) had a sump pump in his cellar. It occasionally ran in rainy weather. When we had a burst lead pipe under the house, it ran a lot (and our Wisteria grew terrifically)

My current neighbour used to have the cellar flood in extra-high tides. Not with seawater, but the underground springs backing up. He had a concrete floor laid to stop it coming up, but did not have a DPM tray so it still got damp.

Modern practice in basements is to have a false floor and walls, allowing water to drain behind and beneath them into a sump that is drained or pumped according to height. Trying to keep water out with tanking generally fails when added to an existing building.

As you have a sunken area (moat) you might be able to have sumps put around the house, and linked together to a pump. I have no experience of this.

But as the water seems clean, it might be that it is coming from a waterpipe that can be repaired or replaced. Not such a big job. Do you have a water meter? Do you have an adjacent neighbour who might have a leak? You can ask the water co to test the water and see if it is chlorinated (indicates tapwater) or soapy (indicates drains)..

Thanks for all the ideas! I’ll ask the damp people (if they ever return our calls).
Any hope it’s condensation? We had that in the cellar under the external steps - the room was covered in mould and a ventilation hole solved it.