Damp cellar at street level

Hello, I posted a query earlier in the week about the damp cellar and I got some useful replies. To date, the Marie hasn’t responded to my email about them investigating whether the drain below the pavement is cracked.
I’m interested to know if anyone has an opinion about whether I could insert vents in the windows and whether this would help. Would I be able to insert a brickvent into this wall facing the street ? Below the steps is a little cellar leading into the main cellar - again could I put a vent on the face of the steps? Also, I’m wondering whether the mortar on the wall on either side of the window is in fact cement or whether its limemortar. Does anyone have a view? Many thanks.

Surely you need to absolutely identify what the problem is - before proceeding. Otherwise, money and work could be a waste.

Did you send a recorded delivery letter to the Mairie??

No not yet. Intend doing so.

What does the drain pipe drain into? The usually just run out into the road as he one further up does. Cellars are often damp, but caused by rising damp, water rising through the mortar/lime/mud etc by capillary action. Have you noticed any difference over the last week when there’s been no rain?

Hi Mark - thank you. No, its a holiday home and I’m in the UK until the end of July. I haven’t looked at what the drainpipe drains into - I’ll do so when I get back though. I assumed it was a drain under the pavement. Yes, cellars are damp places. This one has zero ventilation. There’s also that musty, old building smell which I’d like to get rid off and of course beetles seem to like damp too. I have a feeling the mortar alongside that street level window is concrete, that wouldn’t help at all. Up the street on the far corner is a restaurant and its very dry inside without any mustiness and so I believe there must be something we can do to rectify it. I guess there’s no DPC either which would also help. Any suggestions are welcome.

Have you had any sort of professional look at the situation - or is just an assumption that it is the council’s underground pipework that is at fault ?

Where does the tap water enter the building ?
Where does the sewer exit the building?
Where do the gutters exit?
Is the paving sloping towards the building?
Is the seal between pavement and building watertight?

There’s more than one possible cause of damp and not necessarily easy to pinpoint.

best of luck

Hi, yes those are good questions and I don’t have many answers. I thought a starting point would be to check drainage pipes under the pavement, if in fact, there are any there. I think if I head to the Mairie they’ll have a map of where they are in the local area. I presume. I’ll also get a prof to look when I’m back. I just thought to try get some opinions first so that when I get someone in I could gauge whether or not he was on the right path. The paving looks to me to be a little old. It looks flush again the wall of the house - but who knows.

You mentioned a seal between the building and pavement - I’ve just seen the paving I haven’t noticed a seal.

Where one surface meets another - in order to keep the joint watertight - I would expect there to be a seal of some sort - mortar or whatever is appropriate.

Hi Yes, I can ask a professional if there’s any evidence of one. I haven’t noticed one though.

It might be worth paying a fee for a professional to look at the cellar and surroundings - to identify the source of the damp.

Such a professional would look at all the points we have raised plus others we might not even think of.

Once you have that report, then you can plan the way forward.

That’s just something for you to consider.

Yes, I will do so for sure.

It will be almost impossible to create a waterproof seal between the wall avnd the street, you might be better fitting a fan . Simple bathroom fan with a humidity sensor, or simply put it on a timer. Have friends in Aubusson who had a similar problem, they couldn’t stop the water but it soaks away quickly (gravel floor) and the externally vented fan is keeping the humidity down.

Great. Thank you very much.

Quite agree - there are ways to minimise the effect of damp if the damp itself is unavoidable.

This is a holiday home and IMO the owner needs to find the cause/source of the damp.

It may simply be a case of - what can’t be cured must be endured - but the damp might be caused by a defect which can be corrected.

( we have a beach about 4 inches deep and the damp passes underneath and helps to keep the cellar a constant cool temp. openings on all 4 sides give an air flow as well. We have a natural water source which passes and no longer damages the property)

Hi Fiona,

Perhaps it is good to consider that many cellars under old French houses were intended to be both cool and damp. They were intended for wine storage, and the dampness helps maintain the seal of the cork in the neck of the bottle.

So how to get rid of the dampness ?
Well the first thing to do is to improve the ventilation by creating a through draft either by the installation of vents through the walls or windows, or by installing a fan as others have suggested.
Next, one has to look at the walls. Are they rendered with cement or are they just visible stone ? If the latter, then rendering the walls with a cement mortar made up by using water mixed with 50% waterproof PVA (poly vynal adhesive) will over time (2 to 3 years), both draw the existing moisture out of the walls (and the ground behind them) and leave you with a waterproof surface.
Finally, what is the floor made of ? If it is just a dirt floor, or ‘tommettes’ or something similar laid directly onto the ground without any damp proofing beneath it, then the answer is to lay a new concrete floor with a plastic sheeting damp proof membrane underneath it. (The plastic membrane sheeting should come up the walls at least 6 inches.)

Making the cellar dry will take both time and effort, and will not be achieved quickly. It’s a ‘labour of love’, but if you persist then you will get there in the end as I myself have done.
Happy labouring. :slight_smile:

Hi Robert Thank you very much for your suggestions. Much appreciated. Yes, I imagine it will take time. And as you suggest its achievable. Many thanks.

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Regular PVA will re emulsify in wet conditions and is therefore useless.
It will not draw out the water.
You may need a proper solution which may involve a sump pit and pump and/or tanking membrane applied. A tanking slurry like Sika may work but that needs an on site survey.

I think you’ve hit the nail on the head… investigate the situation … then find the solution (no pun intended) :upside_down_face::hugs:

Thank you very much John. Interesting. Yes, tanking is an option. I posted a picture along with the original post as it occurred to me that the mortar on the external wall is cement. If so, this would add to the problem. I guess a professional will be able
to take a look. I’ll get a few quotes in. I ultimately want it dry and to get rid of the musty smell. Thanks for your time.