Cause of damp Victorian house

[ElsasSalamander]

We have a damp problem in our sitting room on the chimney breast but also in the adjoining alcove beneath the window.

DH painted some damp seal on when we decorated a few years ago but that only seems to have made it worse & spread further up. It’s now around 1m high. See pics.

House is solid walls (built 1910), with shallow foundations. The internal floors are all solid concrete. We suspect the chimney breast may be solidly blocked up at the bottom - there is no air vent & DH drilled through & couldn’t find any sign of a cavity. The chimney breast runs through a bedroom above & it seems to get condensation on it whereas our other chimney breast (open fire) doesn’t.

Externally, there is no guttering or water source anywhere near it. The window does not leak. The original Victorian dpc (layer of slate) is visible around 2 bricks higher than the paving. There has also been a chemical dpc done externally a long time ago (c.30 years). Just been to take pics of the brickwork on the outside & it isn’t looking too great (see pics).

My question is - what are your thoughts on the cause of the damp & what we should do to put it right? Is it most likely to be the blocked chimney or the brickwork or is there anything else I haven’t considered? In which case do we need a builder or a damp proofing company?

I'm no expert, but I reckon the chimney is acting like a wick and sucking damp out of the ground.

I would suggest a builder. I think you need an air vent in both the sitting room and the bedroom above it.
We had a cover placed over the top of our Victorian chimney i.e. chimney capped off to allow air to leave and enter, but to prevent rain water coming down the chimney. I would also ask the builder to check the flashings as well.
It was a fairly quick job for the builder to do.

the chimney must be ventilated top and bottom. Otherwise it will get condensaton inside which will work its way out.

That is easily fixed, given half an hour and a large drill. There will be a separate flue for each fireplace, usually one upstairs and one down.

If you are 100% certain it will never be used again it can be ventilated into the loft (anyone putting it back into use would should test the flues anyway).

Examine the floors for signs of damp. Have you got a water meter? Has your boiler got a pressure gauge?

how near is this damp to the kitchen and bathroom?

External pics

Thanks for the replies.

We had a cover placed over the top of our Victorian chimney i.e. chimney capped off to allow air to leave and enter, but to prevent rain water coming down the chimney.

We’ve got one of these too. I don’t think there’s any issue with the flashing as it was all checked & repaired when we first bought the house but worth asking a builder to check thankyou.

PigletJohn We have already drilled multiple holes into the chimney breast in the bedroom and fitted an air vent, but it still has damp (condensation?) patches on it. When DH tried to do the same downstairs he said it was solid. Despite using a mahoosive drill bit he never reached the chimney cavity and hence why we suspect it’s been solidly blocked up. We can’t ventilate into the loft as we’ve had a loft conversion done.

No signs of damp on the concrete floors. We don’t have a water meter. The damp is a reasonable distance from kitchen & bathroom and there are no water pipes near it. No sign of damp between the alcove and the kitchen (under the sash window). Look at the first external photo - the two windows are the sitting room - the damp is on the corner beneath the tiny window. The kitchen is to the left of the big sash window - the bathroom is above the kitchen. The water mains enter the property in the kitchen. Are you thinking it could be a leak somewhere?

I wouldn’t mind opening up the fireplace if it was deemed necessary. Just want to get this damp sorted so we can decorate!

Agree with egontoast (prob. rising damp, by capillary action).
These houses were built with lots of natural ventilation, which mitigated any dampness; open chimneys with constant coal fires creating an up-draft, + drafty windows, and floors.

1. If you re-plaster (for aesthetic effect, if nothing else). Re-plaster affected areas with lime based plaster (Limelight is one brand). Get a plasterer who has used it before. Aim ? To enable wall to 'breath' and not 'hold' the damp, + use a de-humidifier, in the room, much as poss. Having done, this myself: still get some paint flaking (maybe re-painted too soon), but plaster has held, and not 'bubbled'.

It's possible that the builders changing the fireplace threw all the rubble inside and bricked it up. It may be necessary to open the brickwork and dig it out.

It's not common to have a concrete floor (except in the kitchen) throughout a house this age. Do you think it is original, or is there any suggestion that a wooden floor went rotten and concrete was poured to replace it? Do you see any airbricks around ground level? How old do you think the concrete is?

Your second picture appears to show a wet wall. The brick colour looks different and I think I can see powdery white efflorescence. What is on the other side of that patch? The paving slabs look wet and seem to have black mould due to long-term wet. If your pour a bucket of water on the paving, does it run away from the house and into a drain (correct) or does it lie in a puddle or run towards the wall (incorrect)?

How high above the paving or ground level is the DPC?

Are the signs of (useless) damp-proofing drilling near this wet patch? If so, it means there has been a long-term wet problem, which the chemicas did not repair.

Yes, you have an excess water problem. Water always comes from somewhere. Sometimes it is rain collecting, sometimes it is broken drains; sometimes it is leaking pipes. Chemical injections do not repair any of these faults. A house with a slate DPC can usually shrug off damp from the ground.

If the ground is very wet, it can come up through a bad concrete floor, or through a hearth and rubble in the fireplace. It will not usually rise more than a foot or so if the brickwork is good, though plaster or render can encourage it up.

in your near-full-height pic, there is something resembling a pipe low down to the right-hand-side. What is it?

A friend had damp in her Victorian house because the original damp course/air bricks had been concreted over, which they discovered when they took up the floorboards. They got rid of the concrete and the damp went away. Try taking up some boards near the wall to see if you've got the same problem?

I just typed a long reply and lost it.

Not sure how long the concrete floors have been down or if they are original. Or how I could find this out? They are throughout the ground floor of the house. We’ve been here 12 years so certainly longer than that. I suspect a lot longer. There is no obvious sign internally that the concrete floor is damp though I may pull up the carpets again to double check it all still looks ok.

I’ll check again in the morning for air bricks. Can’t say I’ve ever noticed any.

Your second picture appears to show a wet wall. The brick colour looks different and I think I can see powdery white efflorescence. What is on the other side of that patch?
See Extra pic of outside which shows the area of the damp circled in red and the location of the chimney breast in blue. There has been repointing on the external wall behind the chimney breast (I suspect with normal cement not lime mortar?) but not on the area beneath the window. The bricks there have lost their dark face is the correct term blown? This appear lighter in colour. And yes sometimes it looks white (salt?). This wall is west facing so receives the worst of the weather.

The paving slabs look wet and seem to have black mould due to long-term wet.
It had been raining this morning when I took the photos - the paving is just wet not black mould. In dry weather the paving doesn’t usually appear wet or damp.

I’ll check out the directional flow of water on the path - hadn’t considered that could be part of the problem. Path was laid approx 8 years ago at same time we had the drive done.

The chemical dpc runs right around the house in the brick directly above the slate. So 2-3 bricks above ground level - I’ll measure exactly how high in the morning.

The pipe in the bottom right corner of the full height photo is the gas mains.

I agree with PigletJohn, the slabs look wetter near the problem area and the cement mortar won't help matters (although not the whole cause).

Chimneys built in the era of your house aren't likely to have a DPC even if the main walls do have a slate DPC. This would suggest that you have high levels of moisture below ground.

Looking at the photos the damp is 'active', which isn't surprising this time of year. It could also be a leaky pipe. In this circumstance I'd recommend you get an RICS surveyor to check it out, a salts test of the affected areas could narrow down the cause.

I always try to go down the treat the cause route before employing the treat the symptoms only.

I know nothing but....I too live in a Victorian house with a couple of damp areas.
One of my damp areas looks a bit like your external area and I think, like me, you have several blown bricks where the waterproof face of the brick has sheared off thereby exposing the less robust, more porous inner.
When it rains, this porous brickwork soaks the water up like a sponge and because the wall is waterlogged, it's affecting the internal plasterwork.
Presumably these bricks need to be replaced.
I've done nothing about mine because it's just a few bricks beneath a bay window so, I think, I'll struggle to get someone to do it - it's too small a job for them.
I would be ringing a builder if I had the amount you have OP.
I also think your comment regarding non-use of lime mortar for repointing has contributed to your brickwork deterioration.
That's what has caused mine.

We had a similar issue and had a builder repoint one side of our house, replacing the delaminated bricks (the ones you mention as blown) The problem is now fixed and we have no more damp!

The amount of water in that wet patch is more than a bit of bad pointing would cause. The bricks have been sodden for years. Their faces have spalled off and the mortar has been washed away. It is very localised. The water could possibly be coming down the chimney but it looks more like a pipe.

I have only seen such damage caused by a leak.

Just resurrecting this thread. With winter & covid we’ve only just got round to having this looked at by both a builder and damp proofing company.

Neither tradesmen felt it was a water leak causing the problem. They both said it was rising damp & failure of the existing dpc.

Builder suggested we should remove all the internal plaster and render to just over 1m high & chop out & replace the affected bricks both internally & also externally as once salt was in them it would keep coming through. He suggested getting damp proofing company to install a new dpc and recommended using lime mortar to repoint externally and to use a lime based render inside before replastering.

The damp proofing company also suggested removing the plaster & render internally and have suggested a new plastic membrane & slate dpc which can (mostly) be fitted externally. They would then apply waterproof/damp proofing render internally before replastering. Didn’t seem to think lime render was necessary. Their view was that the internal bricks did not need replacing, as the damp proof render would stop anything coming through and the external bricks only needed changing for aesthetic reasons. They said lime mortar wasn’t essential & cement mortar would do the job just as well as houses don’t ‘breathe’ so it makes no odds.

I’m not sure whose advice to follow? Is it unnecessary to replace the internal bricks? We will definitely have the external ones replaced & repointed with lime mortar. Internally would you opt for the lime render over the damp proof render? I’m just worried by having the damp proof render we are essentially putting a plaster on it - how then does the damp already in the wall escape? Any words of advice much appreciated - feeling more confused now! Perhaps I should get a surveyor out to look first before having anyone doing anything

Check this guy out. Peter Ward has a lot to say about damp. V interesting and all seems to make sense.

www.heritage-house.org/damp-and-condensation/managing-damp-in-old-buildings.html

Argh bloody damp. Love old houses but always full of damp.
I've read your thread and I'd be very wary if getting "advice" from a damp proof company who ultimately want to sell you their product. As you say, if you simply render etc, where does the moisture go? You haven't solved the problem.
Rising damp also at that height sounds mad.
I'd get a surveyor specialising in damp out. I did for my Victorian flat and it really helped. Strangely enough I didn't need a DPC as the damp proof company had told me!
Which magazine has some good articles, I'll try to dig one out - I also used a SPAB approved damp surveyor for my current (Georgian) house - also v good.

How high is this "rising damp" above ground level?

Have you got a water meter?

Have you opened the chimney breast and dug out the rubble?

I feel for you, OP. I have something that looks very similar on an internal wall at the front of the house - no chimney involved. I had the entire front of the house re-pointed at a cost of £3,000, and had the room with the damp re-plastered ... and the damp came back, but in a new place, where there had been no damp before. I'm in despair now. Someone suggested that it could be because my cellar wasn't ventilated, so I have now got air going into the cellar, which has made a huge difference to the swap-like atmosphere down there, and I'm hoping this will solve the problem. Have you got a cellar?

I'll be reading the information in that link above with great interest.

Hi OP,
The which article from 2011 is only available in a shorter version of the original online, but you get the jist www.which.co.uk/news/2011/12/damp-proofing-companies-exposed-in-which-investigation-274087/
For my Victorian flat with various damp issues, ultimately due to wrong plaster, poor ventilation and condensation I eventually got the "Which damp man" out - David Prince. That was some years back but it was about £120 for the visit.
If I had damp problems in my house now I'd do again what we did with this one when we first bought it which was talk to SPAB www.spab.org.uk - free advice - and they recommended a few specialist surveyors in my area. We used one and he was brilliant - strangely enough we didn't need a new damp course chainsaw cut into the whole ground floor for £25k as the architect and structural engineer were suggesting!
I think a lot of building professionals don't fully understand damp so even with best intentions they will often suggest solutions that are inappropriate.
You need to get a specialist surveyor out, it'll be a few hundred quid but you could easily end up saving that 10x over on the remedial works. I can't recommend SPAB enough, as a starting point.
Good luck and let us know how it goes!

Should say - there's loads on the SPAB website but I called their technical helpline and just had a really nice chat. Felt a bit line the Samaritans for damp tbh. I don't think they get many calls, it's a lovely service considering they are just a charity

Thank you @Cavagirl. That's a very useful tip.

Whateveryouwant1 thankyou I shall watch that with interest.

Pigletjohn its 118cm high internally at its highest point though not all the way across & approx 130cm high externally. That’s just in the worst area, where we’ve got it in other parts it’s no more than 40cm high. No we don’t have a water meter. We are going to clear out the fireplace ourselves, planning to start it this weekend.

Interestingly I’ve just been outside - it was raining last night & the wall looks like this this morning. Towards the front the wall looks dry, towards the back (the worst area) the bottom brick looks wet. I checked the water runoff and it seems to tilt away from the house towards the drive but perhaps not enough?

Time40 no we don’t have a cellar. What you say is exactly my worry - we pay either of these tradesmen & it just comes back.

We’ve just had our quote come through from the damp proofing company at £3.7k I didn’t think it’d be as much as that. A quick google says an average £70 per metre, I’d say we’ve around 24 metres to do to go all the way round our two rooms & hallway so £1680 - does that sound more reasonable?

Been trying to find RICS surveyor, there’s only one firm listed in my area (North) on the RICS website - just called them & turns out it’s an estate agents who don’t even do specialist damp surveys & they just use a local damp proofing company. Their exact words were “it’s pointless paying for a survey as they will only tell you what to do to fix it then you’ll need to pay someone else to come and do the repair so you’re paying twice”. Where does that leave me?

Thankyou Cavagirl that’s really useful I will take a look now