F.A.O builders, dampness rising

glasgowdan

I've called a couple of companies about some patches of rising damp in our 1970s extension. It seems to be coming from the one wall (north facing, bordering neighbour's driveway).

I wouldn't mind having a little idea before they visit. Is there any chance that the raised edging, backfilled with mucky gravel, could be a factor?

The wall feels cold to touch. It's a flat roof extension. The wall inside has had built in cupboards which I am removing, and we've found a few piles of clothes with mould on them after under a year in there.

Any thoughts would be greatly appreciated.

DaftyDuck

Years ago, that drive wouldn't have been tarmac, and would have freely drained. Mow, at a guess, half the water is shed to that aged French(ish) drain. It'll have clogged up, soil and organic debris, and it will have raised levels by now anyway. So, worth digging it out, putting in proper drainage, taking drive water well away if possible.

It's also possibly single skinned ?? and flat roofed. That's not going to help, but could improve if you kncrease insulation to both. Cold walls are pretty much bound to attract condensation.

But, since it would be cheap DIY, I'd start with drainage....

In over 12 doer-uppers, I've never found damp that couldn't be DIY cured.

Doozergirl

As above. It might just be the the tarmac has generally raised the levels, but it could also be that the render is breaching the DPC as well, either creats good conditions for damp, both would create perfect ones.

French drain first, see if you can spot the DPC. If you can't then hack back the render beyond the DPC, fit bell beads and re-render.

Rubbishy job but much cheaper than a DPC inside, which won't even solve the problem, but hide it in the walls. Do not touch inside.

glasgowdan

What would I see of a DPC? No idea what to look for.

We plan to have the roughcasting redone for the whole house, so would it be worth makibg sure the firm chip it all away near the base of the wall on that side before the new coat?

Doozergirl

Yes, brilliant, if you're working on it anyway.

Sometimes DPCs are invisible, but sometimes you will see a black plastic membrane poking out. I can't think that we've ever worked extensively on a 70s house so not exactly sure what is normal. Bitumen?

Usually though, you will see the condition of the bricks themselves change from below to above DPC (damp to dry, evidence of moss below etc) or they could even be different bricks altogether.

DaftyDuck

DLC in a 1970's might look like nothing more than a different mortar layer, but there will be a difference, brick, mortar or membrane.

Since it's a flat roof, is the water well shed from the roof, clean fall into gutter?

Any idea if render was added as an afterthought? It's frequently done to hide poor brickwork, or to "solve" water penetration..... which it tends not to do.

Definitely worth chipping it away and getting a good finish to shed water from bottom of wall.

I still think raised and non-porous drive is likely to be main culprit. Followed by render, followed by guttering.

More photos?

glasgowdan

I can't do anything with the drive as that's the neighbour's but I'll try and get a few more photos up later. We got the house guttering renewed before moving in and it's working well.

I'll focus on that drain channel and see what the company coming on monday say.

Doozergirl

What company? Please not one that sells DPCs!

glasgowdan

Well they do specialise in damp issues so I am aware of being extremely sceptical of what they say. In fact I've emailed them as they've not discussed money but if their initial visit is chargeable I'll not bother. I heard a couple of genuine sounding reviews and thought why not.

The problem is no builders are interested in this as it could be awkward to diagnose and is a small job. And I don't have any experience to make a call myself.

I'd hope the walls are cavity but not seen any evidence of this.

Doozergirl

It will be cavity. No doubt. The MSE email this week talks of the two energy companies offering free cavity wall insulation. Book a survey. Those worth their salt can drill you a little hole and video the cavity.

But the depth of the walls from front to back in the reveals for your window will give it away. Anything more than 20cm is cavity. Yours will be close to, if not the standard 30cm.

Damp issues are so hard. There's no money to be made by anyone rectifying the usual genuine little bits of maintenance that cause it.
That's why the industry exists. People have problems but no expertise - the people that sell DPCs and render walls to hide the damp appear to be successful. It does the job in one way, but the best way for the longevity of the house and your pocket involves time - if this is your home and you have a bit, then just trying these solutions should really yield results. If it doesn't, then spend the money, but there's no dire rush if timbers aren't affected. I'm sure you'll have a solid floor.

It's taken me an awfully long time to really trust my own instincts against what the rest of the industry says. I finally knew I was right when my client (who is a very successful developer in his own right) called his surveyor to discuss a 'rising' damp problem at his new (listed) house with me. He recommended a DPC on one wall. I pointed out that it already had three injections!

I got him and his little 'damp' machine around that house and we took readings everywhere. By questioning, questioning, we managed to trace the problem to the roof. It had obviously baffled many people before. And it wasn't obvious, but yours looks pretty simple to me.

It may not work, but if it does, over the of the year, you'll be pleased that your walls are dry from out to in, not cement rendered, blocking the damp in the walls from penetrating through the render.

glasgowdan

I've finally had a chance to dig out the stuff behind the low wall. There was a lot of chunks of roughcast, concrete and stones. It was all quite dry right enough, but it was a nice dry day. A lot of roughcast sections seem to have blown low down too.

My plan now, I guess, is to arrange the house to be roughcast anew right to the bottom of the channel, including chipping off as much of this area as possible. I reckon then I'll get a channel drain In, as there's a slope away from the camera, and have any water flow out behind the hedge into a sink area in the garden.

Appreciate all the feedback. Any thoughts on this plan would be really appreciated thanks!