Damp!

[Jamieharnett]

Hi all,

I’m hoping for some advise regarding damp!

I recently bought a house built circa 1800 which had been neglected for some time. One of the main problems was damp through ground floor. The original quarry tiles had been broken up and then a concrete screed placed on top. I have now removed all the ground flooring and installed 200mm Geocell with UFH and 100mm line screed to help remedy some of the damp.

HOWEVER..... I have two rooms one a kitchen and the other a large cupboard/store/room which have been replastered in gypsum finish with a bonding below. The kitchen has a slight bit of damp on one wall which backs on to the fireplace which has been blocked off. Which I plan to get somebody to open it up again to vent. The house is a semi and in stone which has been pointed up in cement, the conservation officer has refused me to re-do in lime unless next door agree to do the same?! They obviously don’t want to spend the cash as they don’t have any damp to knowledge!

In hindsight I would love to rip out all the old gypsum plaster off and re do in lime but with funds being spent daily and balances go down, financially I cannot afford this at the present time and I need to be able to make this place habitable so we can move back in.

With the stone pointed in cement would lime plaster benefit the house in anyway and with the floors now in lime will this eliviate some damp going in to the walls?

Hey let’s see what you lot think?

Thanks in advance and thanks for all the advice previously.

 

[88v8]

Reopening the fireplace is a (messy) DIY job, so funds need not be an issue, and definitely best done while you are not in residence. If you can't presently afford a fire surround - although you could make one as PlasticPigeon did - just clear out any rubble and put in a brass vent for the time being.
What about the corresponding chimney pot? Is it still there, is it capped, if so with what?

Semi... I would never buy a semi for this exact reason, if one party wants to restore and the other doesn't, if they can't agree on windows, etc.
One can understand where the CO is coming from, but...........
I would quietly repoint the bottom 3ft around the back, perhaps 2ft at the side and the front depending how visible the house is. NHL lime and sharp sand, sand with or without grit depending on joint width.

The Geocell and lime, no dpm, right? So the damp that was being pushed into the walls by the concrete will now begin to dissipate. It takes about a year per foot thickness for damp walls to dry.

In general, with no dpm nor dpc, the house will always be a bit 'damp'. The damp may eventually not be visible, but it will always be there in the air and if you buy a hygrometer or two you'll be able to keep track of your progress in drying out, and see when you get to a base level.
https://www.amazon.co.uk/Thermometer-Hygrometer-Instrument-Room-Control-Anthrazit-White/dp/B002U9U4B4
Our cottage sits at about 70% in the summer, and down to 45% in the winter.

Good ventilation will always be essential. Opening up fireplaces, extractor fans in kitchen and bathroom, no drying clothes indoors.

I'd buy a dehumidifier and run it 24/7 - other than in the summer when the windows are open of course.
The Ebac 2000 is a good one, sometimes available on eBay, quiet in operation.
https://www.ebay.co.uk/itm/Ebac-2000-series-18L-Dehumidifier-White/153126297733?epid=1321958517&hash=item23a709e085:g40AAOSw65FbZYmU
It will also accelerate the drying out process.

Ivor

 

[Flyfisher]

One can understand where the CO is coming from, but...........
I would quietly repoint the bottom 3ft around the back, perhaps 2ft at the side and the front depending how visible the house is. NHL lime and sharp sand, sand with or without grit depending on joint width.

Yes, an interesting conumdrum. I wonder if Ivor's suggestion could be argued as being a 'repair' (no LBC required)? Besides what could/would the CO subsequently do about it anyway - force the replacement of the lime pointing with cement pointing? Unlikely I'd say.

Of course, ignoring the CO's advice (indeed, instruction) would annoy him/her intensely so is not an easy option and also not generally recommended as the ideal is to have them as allies not enemies, but I can sense the frustration.

I'm assuming the CO's objection to replacing the cement mortar with lime mortar is basically an aesthetic one - and, as Ivor says, is sort of understandable - but what about using a suitable pigment to make the lime pointing match the cement pointing of the neighbouring semi? I'm only guessing that such pigmentation is even possible, but it might be worth a friendly discussion with the CO about it to see if it would alleviate his/her concern.

 

[plasticpigeon]

There are a couple of COs on here so they can give very well informed answers. I am amazed your CO doesn't want you to repoint in lime, and if I was in your shoes I would contest this as I'm pretty sure it would be a repair, and one that would safeguard the stone from possible future deterioration. If it is an aesthetically driven decision you can make the colour match as has already been said!! I think changing the floor as you have done is probably the most important thing. I'm a little sceptical about the necessity of lime inside, especially with the change of floor as now the ground under the walls shouldn't be so wet. I would be inclined to open the fireplace and put a cap on the chimney that allows ventilation but doesn't allow the rain down. Hopefully then the walls will dry and the gypsum can stay.

 

[malcolm]

My kitchen was also plastered in bonding plaster with a gypsum skim, I guess because it had been damp. I notice the modern stuff didn't fix it (picture below). I suppose people did that sort of thing to try to fix damp so you might well have an issue that still needs to be fixed.

I had just about every possible cause of damp outside - waterproof paint, overflowing gutters, outside ground levels higher than inside floor levels, leaky drains, rotten windows. and someone stole the lead flashing from my attached shed! I hacked the plaster off a year after mostly sorting out the problems outside and the bricks were pretty dry apart from the wet patch where I hadn't got around to fixing the drains.

My guess is if the causes of damp are fixed then the silly wall covering is probably OK. (Mine had failed and I needed to add insulation for building regs change of use so needed dry and breathable.) For the chimney just venting the top while keeping the rain out can do a lot. I put a paving slab propped up under one edge with a roof tile on one of mine and just doing that starved my chimney triffid of water and happily caused it to depart this mortal coil. I would be keen to get rid of the cement pointing outside - it has ruined the little stone that I have.

 

[ElectronicFur]

I've also been looking at the humidity levels in my house, as it feels more damp than our old house.

The last 3 days it has ranged from 60 to 72 RH. Now I read that ventilation will help with humidity, but opening extra windows etc, didnt seem to make much of a difference. It was only then that I though to put the meter outside. The humidity read about 66 RH.

My initial instinct was to get a dehumidifier, but after reading https://www.heritage-house.org/damp-and-condensation/controlling-humidity.html I thought I'd investigate ventilation systems instead, as the author rejects dehumidifiers out of hand.

But I dont see how extra ventilation using ventilation systems or opening windows will help in this case if the humidity of the incoming air from outside has 66 RH. Of course I don't know if this week has just been especially humid outside in our area, maybe more monitoring is required.

Has anyone had success with the type of ventilation systems mentioned by heritage-house?

 

[88v8]

There have been some proponents of these forced ventilation systems on here. Not an easy retrofit.

A humidity controlled extractor fan for kitchen and bathroom however, is easy - just needs a humidity switch.

The Met office tell me today's local humidity will be 88/65%. This of course is one reason that humidity indoors is higher in the summer. the doors and windows are open !
In winter we light the fires and close the windows so we're force-drying a closed system.

Dehumidifiers do indeed treat the symptoms, another way to look at them is that when one has done all that is possible they do a little more. In our cellar, the dehumidifier reduces the rh by around ten points, about half a gallon a day.

If the OP has done his floors recently, it will take a while for the walls to begin drying. Lime pointing the lower few feet would help.
Aesthetically, our (stone) cottage was cement pointed inside and out in the 70s. Luckily it has not harmed the stone. The PO dealt with the internal aesthetics by meticulously painting the pointing with stone-coloured Sandtex.

Ivor

 

[Flyfisher]

From that Heritage House link: "We have joined forces with . . . " Hmm.

You can buy some superb units that will help solve your problems. There are two ways of doing this - dehumidifiers, and mechanical ventilation. Dehumidifiers can be rejected out of hand - they do not cure the problem, they treat symptoms. Dehumidifiers are very expensive to run and need constant attention - you have to empty them and clean filters.

That reads like a very biased assessment to me. Firstly, BOTH dehumidifiers AND mechanical ventilation systems treat the symptoms. NEITHER will cure the basic CAUSES of high humidity in modern homes due to all the reasons described on that very same webpage, ie Humans are the worst enemy of houses. It is what we do inside them that causes damp problems. Breathing, Cooking, Showering, Gas Fires - all these produce moisture which has to go somewhere . . .. Yes, all that moisture has to go somewhere and BOTH dehumidifiers AND mechanical ventilation systems remove it from within the house, they don't PREVENT it at source, so that doesn't seem to be a good reason for dismissing dehumidifiers 'out of hand'

Secondly, why are dehumidifiers "very expensive to run"? Where are the comparison costs for mechanical ventilation systems?

As for dehumidifiers needing "constant attention - you have to empty them and clean filters", the first is simply not true and the second is a matter of opinion. If a dehumidifier can be installed near a drain outlet then it will NEVER need to be emptied. If, like mine, a dehumidifier is installed in a cellar with no drain outlet then a simple and cheap 'condensate pump' can be used to pump the water away to the nearest convenient point. In my case, this is out through a ventilation grille about five feet above the floor of the cellar. The dehumidifier drains into the condensate pump and when it has collected about a pint or so it automatically pumps out its reservoir, a process that takes only a few seconds so the pump actually runs very infrequently.

As for "cleaning filters", well yes, but I wouldn't say once per year qualifies as "constant attention".

But then I haven't "joined forces" with anyone so have no vested interests in either option.

 

[Flyfisher]

.

 

[ElectronicFur]

I agree Flyfisher, it does seem somewhat biased.

Meaco has some decent dehumidifiers that only use about 270W.

Humidity controlled extractor fan for kitchen and bathroom as Ivor suggests might also make sense for us as our bathroom seems to get to about 82 RH after showering, and takes a while to lower with just the window open and the door closed. Opening the bathroom door speeds things up, but then I'm guessing the humidity spreads into the house as well.