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?

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”.
Channeling Mandy Rice-Davies here but - they would say that, wouldn't they?
Good luck OP & keep us posted.

I was just surprised that what was meant to be an RICS surveyors office would say that!

That wall has such bad water damage that I cannot doubt it was caused by either rain cascading from a gutter, or from a leaking waterpipe.

Do not waste your time and money on a company that will apply chemical injections. They don't cause leaks. Nor on anybody who wants to hide the damp patches behind render or plaster.

You already know you have a problem with the chimneybreast, so open it up, dig out the rubble, see what else you find when it is open; leave it ventilated top and bottom and peer up it with a torch. Break and dig out the old hearth beacause it will not have a dpm and take it down a foot or two. If the footings are damp, the water will find it difficult to climb up ventilated and un-rendered brickwork. It can climb up builders rubble with ease.

Do you know where the outside stopcock is, and the route the pipe takes under the floor?

If you are North west I can give you the name of an independent damp specialist who I have used and found to be absolutely brilliant. Came to look at our old Victorian house when we had issues

Thanks Allbelly we are Lincolnshire/Humber area so might be a bit far.

Pigletjohn thanks for the continued advice I really appreciate it. I hear what you are saying about water leaks & can say with 100% certainty it’s not a guttering problem as there is none on that side of the house. I cannot however be certain about external underground water leaks & this worries me. How do we go about ruling that out if we don’t have a water meter? We’ve no loss in water pressure it’s very strong. I’ve attached a plan showing the route of the pipes & location of the stopcock if that helps? It’s towards the front of the house.

We’ve actually had an independent surveyor look at the damp this morning - his view was that the fireplace was the problem. We removed the skirting while he was there & it was very wet & crumbly behind it and in the fireplace area the cement render touches the floor.

He said much the same as you Piglet that we would be best to clear it & make sure we could see the slate dpc all the way round (it was breached by render in a couple of areas). He also said that there wouldn’t be a DPM under the hearth but that he would probably just leave the floor as it is. I think we’ll take a view on that once the fireplace is opened up.

DH has taken off all the plaster & render so we can now see where the fireplace was. It’s huge & it looks like it’s been bricked up twice. We haven’t got it fully opened yet - the centre bit is so solid it’s snapped DH’s SDS drill bit! There is a wee gap right at the top though & there is soot pouring out so it must be pretty full of it.

Forgot to attach pics

late at night, when all is quiet, turn off all radios, fans, fridges and put a young person with sharp hearing in the kitchen.

have another person turn the outside stopcock in or next to the pavement on and off.

An underground leak is just faint white noise, but with good hearing the young person will notice when it stop and starts. Like when you are in a room with air conditioning and it turns off.

or, press the tip of an Engineers stethoscope to a cold-water pipe while the outside stopcock is turned on an off. A wrinkly old plumber will know some other techniques.

underground water pipes commonly leak after 50 to 100 years.

The water pipe in your diagram takes an unusual route. In a house of Universal Plan, it usually runs under the hall floor to the place where the kitchen used to be when the house was built.

It might also be a leaking radiator pipe, which you would notice because the boiler pressure would keep dropping, or the feed and expansion tank would keep filling, and because your radiators would be rusting from the inside.

if you are breaking open the chimneybreast, get a builders canister vac. Builders dust will ruin your domestic vac.

This one is wet and dry, meaning it can also suck up water

Buy a spare cartridge filter and spare bags. Do not buy a vac that you can't get spare bags for. They delay clogging of the more expensive cartridge filter.

Similar machines are sometimes sold in Aldi and Lidl. The plastic tools are poor quality but you can buy replacement sets on ebay by quoting the connection size.

They are quite noisy.

p.s.

I think your sketch plan is of the drains. Not the waterpipe.

p.p.s.

either or both could be leaking.

Thankyou for the tip on the builders vac that’s useful! I think we’re going to get a builder to look it over before DH starts taking bricks out.

The surveyor looked at our internal water pipes. They are all above ground not under the floor and there are none in the worst affected area.

Sorry about the plan - you are right it’s just the sewer. I had assumed the mains water follows the same route since the stopcock was alongside the drain but don’t know for sure. I’ve re-attached the plan showing the location where the water supply enters the house in the kitchen. This is where our internal stop tap is located. I’ve also put on the radiators so you can see where they are. The ones in the back room is piped from the kitchen & the front room and hall are fed from upstairs.

Re the outside stopcock - thanks for the advice - it’s something I would definitely like to try. We unfortunately have an additional challenge in that it may have been buried under our driveway when we had it resurfaced a number of years ago. It was next to the manhole cover & now it is no longer there. We didn’t notice this until recently & DH has had a dig under the gravel but can’t locate it (it’s compacted hardcore beneath). We don’t know where it is. There is another one on the road but we believe this would also switch off our neighbours supply. I don’t know if we could use that one to do the same sort of check if she agrees?

Hiding stopcocks and manholes under paving is one of the things idiots people like to do.

Most often the pipe runs in a straight line from a stopcock in the pavement near where the front gate used to be, under the hall floor, and comes up where the kitchen sink used to be when the house was built. They are supposed to be buried around 450mm deep but you can't rely on it. Sometimes if you find a pipe and look at its orientation, you can guess where it goes. Iron pipes come in straight lengths, lead pipe can easily bend. Modern plastic pipes easily bend, but modern diggers tend to dig in straight lines.

If you do the on/off test after your neighbour has gone to bed, when all is quiet (the best time) they won't know you're doing it.

People who specialise in leaky pipes use hi-tech equipment like flow meters and underground microphones to find pipes and leaks.

You could try David Watt of Hutton & Rostron, heritage surveyor - www.handr.co.uk. Good luck.