Damp in our cottage

[alihBC]

Dear all
I am new to this exciting informative forum and hopefully the expert knowledge on here can help educate my husband and I.
We bought a property (originally a brewery in 1600 and then converted into dwellings/cottages in 1800) in Devon in July 2022.
The survey (Level 3) we needed a damp survey as there were high levels of damp. The surveyor was not sure if the property had cobb walls although the EPC said it did but he found some stone walls in the garage ?!?
We had a damp survey done and they said to:
remove plaster up to 1.2m
inject a chemical damp proof course
render with waterproof sand and cement render mix with an added sulphate inhibitor
skim with mulitifinish plaster
The work went ahead to the cost of £6000.
We moved in ..... I could smell damp when it rained and feel wet droplets on the ground level where the skirtings should be.
We complained.
The company said it needed to dry out. I didnt believe them. We complained to the Property Care Association.
The company came out and dug an external slim channel to the exterior, right and left of the chimney breast.
The company internally tanked (a tanking slurry) these areas to the left and right of the chimney.
I am learning a lot about period buildings quickly.
I believe the chemical injection and the tanking slurry was the wrong course of action.
I have sought legal advice.
The question tonight though is:
If I win the case and the £6000 back I still have injected walls and some areas with tanking slurry on?!? How can you rectify that?? And to what cost??
Just to mention there is a blue plastic membrane which is visible on the ground.
There is Eggshell on the walls.
The house has been rendered.
I look forward to your responses
many thanks

 

[Stevers]

Personally I didn't want to be the bearer of bad tidings when I have no personal experience of cobb, just old houses, but here goes anyway. You're not the first to be had by the damp wallies, back in 1997 they got me, and you will probably need specialist help to devise the minimum solution to the problem you now have. As a matter of interest was the property unoccupied or poorly heated when it was found to be 'damp'?

Good cobb houses are built on a stone base, so stone is often to be found low down in a cobb wall. Gypsum plaster over a hard cement render even without the cement slurry will lock moisture into the cobb; this you now appreciate is bad news. The injected DPC is unlikely to have been effective, and can't be undone anyway. Externally you'll need to make sure that there's a good overhang of roof to walls so that the cobb doesn't get splashed. You'll also need to check the exterior for cement render and modern masonry paints and if found they really ought to be removed for the long term good of your home. In my experience NHL plasters are very good at drying out walls, and as this is a cobb house, NHL 2.0 is as strong as you'd want to go. Applying NHL renders and plasters won't be a problem to a competent tradesman as even I can manage it. You've just paid to have soft plaster knocked of and hard render applied, and that's not an unreasonable starting point for the cost of what comes next, but you may well need to budget for the same sort of thing on a greater area outside, as that may be what caused the original internal finishes to be 'damp' in the first place.

Because modern living produces a lot of moisture, you'll need to think about a good strategy for heating and ventilating your home when the remedial works are complete. I'm a huge fan of 'smart' heating systems that can provide some background heat round the clock, and where real warmth can be programmed to follow you round the house, room by room through the day as you need it; we have had the Drayton Wiser system for a year now, and it's been a life changer for us in our big old stone house.

As an aside, in our case with very solid stone walls I've found it possible to 'fix' some of the damp wally's work by knocking off the blown pink finishing plaster together with a thin layer of the cement render underneath. I then apply two coats of SBR cement slurry followed by a skim of Thistle One Coat. I did this to a new area a fortnight ago, and once again I could not believe how long it took for 3mm of gypsum plaster to dry; a whole week with gentle heat, and that has to be significant. It's a bodge definitely not to be tried with cobb!

 

[alihBC]

Hi Stevers

The Damp Wallies did make me laugh.
In answer to your question the house had been rented but sadly the tenants had not looked after the house so there were leaks from showers / toilets etc.
I really appreciate your time.
I was wondering if the injected DPC could be reversed and can see from your comment - it can t.
Yes I feel I need a independent damp specialist to give us a plan moving forward. I appreciate the gutters / overhang is a good starting point. I just need a bit of cash to employ the independent specialist and hopefully I will get that from the small claims court ?!?

With regards to heating the cottage I have a new boiler and have started to not allow the cottage to go below 16 degrees. Please advise what 'real warmth can follow you around the house means' Do you have sensors in each room pls?

Good luck with your old stone house! Sometimes I loathe this cottage (washing black mould off) but mainly I love this cottage and feel privileged to live here.

With many thanks again

 

[Stevers]

Hi Ali,

Some photos of your cottage might give us more of a clue as to what you might need doing. Not convinced that it's a 'damp specialist' that you need as one of those put you where you are now. Perhaps others can suggest local tradesmen or building surveyors who know their way round cobb and other traditional buildings that need to function without DPCs and DPMs.

On the heating front this might get you started:
https://wiser.draytoncontrols.co.uk/

In our set up all the radiators bar the by-pass rad (shower room) have a battery powered TRV that is motorised and turn themselves on and off according to their own schedule to meet the temperatures that we set for each flexible time period on a phone app. The shower room rad (and boiler) only come on when at least one of the other rads is calling for heat. We care for my elderly mother, and we have programmed extra heat to follow her around the house, otherwise we'd be saving money. We can cater for my son working from home upstairs during the day, and my mother sleeping downstairs with a lovely warm bedroom at night, which wouldn't be efficient with just floor zoning. All rooms including a basement have heat 24/7 with 14C being the minimum for most rooms overnight. Because of the more efficient use of heat we are all more comfortable, but use no more gas than before. On my system it was pretty much plug and play as it already had an ACL Drayton control box and TRVs, and I was easily able to get it all up and working in a couple of hours, so for me just the cost of the kit (13 rads) from an outfit in mid-Wales. With the current price of gas I reckon it will have paid for itself within two years.

With old houses the laws of thermodynamics are somewhat against us, and there may well always be rooms where black mould will need to washed off periodically, in our case it's the breakfast room that is open to the kitchen - closed doors and extractor fans are definitely our friends when cooking in an old house!

 

[alihBC]

Thank you so much for your time.
The Drayton controls seem genius. I shall investigate further.
Indeed I will upload some photos when I have a bit of time as I really think the people on this forum have a lot of knowledge and expertise.
Thank you again

 

[elizabeth]

Good morning ailhBC,
We live in a typical cobb and stone cottage and can relate to your experience in terms of damage created by trades people misunderstanding the right methods for these properties.

Our walls were coated internally with very thick cement slurry and ‘black jack’ was painted over this a meter high then it was gypsum on top. We worked like Trojans to clear this taking care to retain as much cobb as possible as some of it was dry and turned to dust. Cobb relies on a certain amount of moisture to bond and be strong. The wrong coating destroyed the top layer.
I agree with Stevens that you may not need a damp specialist to advise you as the simple answer is to read as much material as you can on the care of Cobb and try to make a list of things you can do presently to make a difference such as ensuring a constant background heat, Cobb walls have thermal mass and don’t respond well to constant temperature changes, ventilate and ensure moisture is managed with extraction besides other steps.
There is a wealth of information here and I have been very grateful as it have informed us a lot.
In the long term look at removing as much of the non breathable material as possible internally and externally.
We did a fair chunk of work ourselves and then sought the help of lime specialists for some of the work. It will have some costs but it will go along way to helping your home. It may take years but that goes hand in hand with old properties.

We don’t mind if you are nearby showing you the changes we have made and if you can gain some insight if you would like to visit you would be welcome. We are Mid Devon.

 

[alihBC]

Good Morning Elizabeth and Stevers
Thank you so much for your responses. It is so much appreciated.
I would love to visit your cob house one day. I live in Woodbury so mid Devon is v close.
Pls help me anyone

 

[alihBC]

These are not cob walls ?!? These are brick walls is that correct?
Honestly my head is befuddled.
So if they are stone walls it was ok to chemically inject them? Apply tanking slurry to the areas left and right of the chimney breast?
I still get the smell of damp and where the skirtings should be they have droplets on after it rains.
Do u think this is a problem with the flooring ? It is a floating floor apparently.
I am still in cahoots /legal battle with the damp contractor and they say:

As a gesture of goodwill, we are prepared to return and plaster the returns on either side of the chimney breast in a lime render in accordance with English Heritage's specification.

Is that necessary ? It s like the damp proofer (who I have no faith in) is speaking in double Dutch?
Don t I need the flooring sorted?
Any advice
Greatly received
Best
Alison

 

[Stevers]

Those are brick walls, but it could still be cobb higher up - how thick are your walls? Chemical injection doesn't resolve the problem of salts, even if it was effective against rising damp, which is questionable. Though if it never, ever works for anyone, anywhere, why do they do it? I'm not familiar with English Heritage's specifications, but on the face of it, re-rendering in lime mortars and plaster would be a good place to start, and your Damp Wallys might learn something from it.