Damp in Snug 1600 house

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Damp in Snug 1600 house

Post by Jjones » Sun 3rd Jan, 2021 12:24 pm

Hi, this is a call for help. What steps should I take to make this room dry and useable?

My family and I have recently moved into a house. The oldest section of the house seems to have damp issues a room we would like to use but currently don’t.
Pic of room
C6B2C107-C6F5-4894-B7A3-42E10693FC64.jpeg (24.38 KiB) Viewed 647 times
I initially noticed a damp smell in this room and that the plaster had blown away up to a foot from the floor. Also the electrics were tripping whenever something was plugged in. Since disconnected. In addition the previous occupants used the room to grow plants.

I will list the symptoms here

Always damp stone in chimney
Damp stone
61041300-269B-4994-A114-46AC36CC435A.jpeg (28.77 KiB) Viewed 647 times
Smelly room (has improved)
Blown plaster and render (cement plaster)
Rotten carpet fastener and carpet underlay close to walls
Poured concrete floor coming away near wall, exposing damp proof membrane (Does not reach wall) and liquid membrane painted upto first stone.
Floor and dpm
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I have tinkered with the room, pulled up carpet and knocked off old plaster and render. I have also put in a constant source of heat in the room. The smell has really improved. It looks as if the exposed stones have lime mortar but have been capped with cement and pea sand mortar.
The internal damp stone seems to line up with a wet stone outside
We have also had a french drain dug outside the house this exposed an air brick which was underground, it suggests that at some point the room had a suspended floor. It is now a concrete floor. But could be dug up.
Interestingly under the radiator there is a hole in the wall which seems to have a breeze. Not a clue what this is as it doesn’t match with a hole outside.
Also the concrete floor and dpm does not go up to the wall about an inch short. It looks like the gap was painted with liquid dpm or some such and then filled with mortar.

The house is solid standstone on footings.
The room has three external walls and is ca. 12 ft square.
Has a double radiator with 10mm pipes. Very poor flow and slow to heat. We look to replace with 15mm pipes in the summer.
Electric osmosis system throughout ground floor of house drilled into wall. Have been told this is useless. System came with the house.
The outside of the wall is lime mortar capped with cement.

So really this is a cry for some advice. I don’t intend to do the work myself but any help on a strategy to remedy would be most appreciated.

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Re: Damp in Snug 1600 house

Post by ElectronicFur » Sun 3rd Jan, 2021 9:02 pm

Sounds similar to one of our rooms, where flagstones on soil had been covered by dampproof membrane, then wood flooring and then carpet.

The flagstones couldn't breathe as they were covered, so all the moisture went up the walls instead affecting the wallpaper, lime plaster was soaking, skirting soaking and riddled with woodworm of some sort, awefull damp smell, etc.

Removed all the carpet, wood flooring and dampproof membrane and all the damp issues went away after letting it all dry out for a year.

Sounds like you also have a problem with cement plaster inside, and the cement outside. Cement it not great for traditional buildings as it is not breathable like lime, and so traps moisture.

Also I would investigate the air brick underground further, because that would indicate the outside level was raised at some point, and that could be a cause of damp issues too.

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Re: Damp in Snug 1600 house

Post by steveb » Sun 3rd Jan, 2021 9:43 pm

could be worth getting some smoke pellets from a plumbers merchant and see where smoke either comes from or goes to

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Re: Damp in Snug 1600 house

Post by MatthewC » Mon 4th Jan, 2021 1:33 pm

Welcome, JJones, you've found the right place for help. Lots of advice here so ask away (but do search for old posts as well).

The root cause of your dampness is the concrete floor plus the various damp proof attempts. Once water gets underneath it has nowhere to go until it gets to the walls at the edge. There is no great value in heating the place as the dampness simply absorbs the heat - as long as the base of the walls are damp the temperature will not improve much - all the calories you put into the air go towards converting water into water vapour (look up "latent heat of vaporization") instead of heating the room.

You say that the floor could be dug up. In my view that's the way to go, and you could lay a limecrete floor which would allow the water to dissipate. I did one in my kitchen/diner (20' x 12') almost ten years ago(!!!) and it has been great - the house is warm and dry. I assume that your French drain is lower than the floor level inside? If it is, and if you have sorted all other sources of dampness (primarily the roof, rain water goods, drains and chimney pointing/flaunching), then the limecrete floor should do the trick so long as you don't seal it or lay something non-breathable on it!

You can read about my house and the floor on my blog (click the contact thingy on the right and then the blue circle). I bought from Mike Wye (other suppliers are available) and they basically designed the floor construction for me, and gave copious advice.

Could you add a general location to your profile? Sometimes it makes a difference to the advice!


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Re: Damp in Snug 1600 house

Post by Jjones » Tue 5th Jan, 2021 2:58 pm

Thank you all for the advice, this is most helpful. I do have some more questions.

If the poured concrete floor was removed. What would I expect to find? Could the wooden beams still be there? Also do I have to give the room a year to dry out before doing anything? What would be the first step dig out a small corner and investigate?

On the airbrick, it was under the patio outside. When part of that was removed and the french drain was dug it was exposed, it is currently in the french drain, which has a perforated pipe and is filled with washed stone. So the airbrick is just above the footings. Thinking of the age of the house I can’t imagine that the airbrick is original and was added some time ago with a suspended floor?

I have to say the whole house is poured concrete, if we limecrete one room how do you manage the threshold into a poured concrete room?

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Re: Damp in Snug 1600 house

Post by ElectronicFur » Thu 7th Jan, 2021 1:13 am

Jjones wrote:
Tue 5th Jan, 2021 2:58 pm

Also do I have to give the room a year to dry out before doing anything? What would be the first step dig out a small corner and investigate?

On the airbrick, it was under the patio outside.
Well a year is how long our room took, but then our house has walls more than 50cm thick in places, and no heating in part of it currently. A humidity sensor that shows relative and absolute humidity is cheap and can show you the progress.

I'd want to be sure there are no other airbricks below current ground level or other potential sources of water. Elsewhere in our house we've found problems with wet walls from overflowing gutters, blocked drainage channels in the cobbled yard, and even a leaking pond liner.

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Re: Damp in Snug 1600 house

Post by 88v8 » Sun 10th Jan, 2021 11:46 am

Jjones wrote:
Sun 3rd Jan, 2021 12:24 pm
What steps should I take to make this room dry and useable?
What Matthew said........

Our sitting room was damp. 1620 cottage. 1970s concrete floor, dpm, cement pointing inside and out, high external ground level. It felt cold. The Gripperods were rotted, and the edge of the fitted carpet.

We had the concrete floor removed and the dpm. Replaced with limecrete. Binned the fitted carpet. I am always suspicious when I see fitted carpet in an old house.
The cement pointing has been removed internally - still present externally but only a thin skim although I should remove that too.
External level lowered with a retaining wall and French drain.

Remove the liquid dpm as far as possible so that the whole structure can 'breathe'.

Where the new limecrete abuts the old concrete at the threshold just put in a bit of dpm sheet to prevent new bonding to old, then if/when you continue the limecrete project there will be no damage as the concrete is removed.

No, any old beams will be gone, or in the unlikely case that they were left they will be rotted. A single air brick is interesting but not conclusive of course. Perhaps an ineffectual effort to ventilate a damp underfloor, or perhaps there never was a suspended floor.

Drying out of damp walls, reckon a month per inch thickness.

The floor finish for the new floor must be permeable. Stone, quarries, laid and pointed in NHL lime. No tile cement, no modern grout, no cement.
Any carpet must be permeable. No plastic. Wool, with felt underlay is fine. Turkey rugs are good.

10mm pipes... minibore was an 80s fad. I hope there is no more in the house.

The hole in your wall..... all stone? Likely to be two skins, with some bonding stones depending on quality, rubble core. Sort of solid.
May have been bedded in clay rather than lime, with just a lime pointing. Over time, the clay dries out, the wall becomes leaky. While the cement pointing was out of my wall (winter 2011), the wind whistled in even though one could see no holes.

To manage expectations.... when you are done and it is all dry, by modern standards it may still be damp. Depending on the underlying water table. In summer, expect an RH up to 70%. In contrast, when you are in there and lighting the woodburner every evening the RH will gradually pull down to perhaps 45% which would be 'normal' by modern standards, but as soon as the fire season ends it will start to climb again. The limecrete breathers... it breathes the underlying damp into the room....
The open fireplace - or stove with open dampers - will help in summer, but not much, hence the 70% RH. Central heating is not that helpful with damp. It does not create air movement in the way that open fires do when they are alight, I think of fires as consuming the damp.
In our 'dry' sitting room, we have a permanent dehumidifier (Ebac 2650). It works hard in summer, hardly at all at present.
There are not many things that are better about a modern hose, but damp proofing is one of them. Your house cannot be made like a modern house, as the futilities you have enumerated demonstrate.
However it can be made a lot better than at present.

Btw, avoid exacerbating any damp issues by using plastic (vinyl) paint in the house. It causes condensation and mould. Our cottage is liberally slathered with the stuff. Sigh.


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