UKH

There is a wide range of experience here, amateur and professional, so...

Victorian end terrace house. Roof in good condition (replaced 2 years ago). 

Rear elevation rendered at bottom (ground floor) but bare brick above; pointing not great.  Chemical DPC injected at foot ~10 years ago.  Render finish to windows poor and the top "edge" where it goes back to being plain brick is scrappy and flat.  Looks like a bad job.

Side is brick, repointed well in top half,  painted below on ground floor.  No DPC

Front elevation rendered; no DPC

All walls come down to paved ground; no soil and below floor level.  Airbricks clear.

There is quite bad damp on the side and back and a bit at the front round the base of the door.  The paint of the side is flaking off and some of the brick feels soft in places.

What to do?  Options - from various people who've come and sucked their teeth include (but not limited to):

- French trench all round.  I've heard mixed reports

- Injection DPC again - also mixed reports.  This is the go-to solution of damp companies, whose business is, after all, to sell injection DPCs

- Repoint rear and try to get a proper drip line onto the rendered part

- Render the back and side fully

- paint sealant on the bricks then paint; again seen warnings against this

At the moment I'm inclined to fully render/re-render the back and side, but interested in advice!

Thanks!

Is it a cavity wall? Or single leaf? 

I'm a structural engineer rather than an architect, so a little bit out of my zone of knowledge... but I don't believe repointing will make much difference. Basically the brickwork itself is permeable (hence the reasoning for a DPC, which stops damp rising up through it). So if the moisture is passing through the brick then repointing just the mortar won't do much.

My understanding is also that rendering the exterior face of the masonry may actually make matters worse if the damps already in the wall (as you're now preventing the damp drying out externally by preventing air reaching it).

Hopefully someone more knowledge csn chime in!

Another structural engineer with similar knowledge caveats but...

I'd be suspicious of both the render and painted wall. Both may well be preventing moisture leaving the wall. Possibly worth removing them and waiting say 6 month to see what happens. May solve the problems cheaply.

Also if you do re-render, read about lime mortar rather than cement mortar. It is generally considered a better option as it allows moisture out

Oh, don't believe a word DPC companies tell you.

Thanks both.  It's single skin (victorian) in mellow London stocks.  The brick faces are ok-ish but they're like blotting paper if you splash them (or whatever modern analogy I should use for blotting paper).  The rear has an injected DPC but that doesn't seem to be helping!

Any views on French trenches?

Yes, they have a product to sell.

We had the rear roof replaced last year and the gutter enlarged becaus eit was washing down the wall in storms.  Surely that can't still be the root cause after this summer?  How long do they take to dry out?

They are basically land drains which will help keep the base of walls dry. This may help if the issue is rising damp, but it probably isn't. I'd be cautious about digging trenches by all your walls too. This is a structural issue as the foundation (more likely just brick footings) rely on compact soil being at the sides as well as underneath. It might be possible in sections, but expensive.

​​​​​​Unlikely Id say as presumably that was a local issue? That said walls in our house have taken over a year to dry but they are 2' stone.

The way this headache has been going, moving might be the cheap option!

Are the neighbouring properties similar? Do they have damp? Worth looking at similarities/differences?

I live in Victorian semi and have done a lot of fixing up over the years including French drains which do work (and weren’t that expensive in the grand scheme - depending on what is on the ground outside could easily be a DIY job). But we have a damp course - for me that is an essential. 

worth looking at masonry cream, I’ve tried that recently for the one section of our house which is single skin 9 inch brick work (rest is all cavity):

https://emperorpaint.co.uk/the-invisible-insulation-barrier?gclid=EAIaIQobC...

Apparently it is waterproof but breathable (unlike eg Thompson stuff). Too soon for me to give a verdict and I’ll only doing as preventative measure. In grand scheme of owning an old house it’s not that expensive - would only be good brick I think though and not the rendered bits you mention  

if it were my house and I was going to stay there I’d be looking at the dpc option closely, combined with the masonry cream and a diy French drain. 

Try knocking on the door of whoever lives at the other end of your terrace and see if they will chat to you. Interesting if they had damp problems and how that went, or if there's something peculiar about just your house.

I wouldn't want to speculate any solution without some guess as to the cause 

Possibly worth spending 30 quid on this book:

https://www.heritage-house.org/products/the-warm-dry-home-1.html

The author is a bit of an opinionated sod but once you get over it in the first couple of chapters (or skip them) then it will likely teach you something.

I would start with a French drain though, to stop rainwater splashing on the wall, assuming nothing else is out of whack.

Thanks everyone.  The other challenge is getting anyone to do external renovation/building jobs.  So far 8 contacts regarding painting the woodwork; 4 visits - all enthusiastic at the time; one quote...but that turned out to be a chap with no TPL insurance and a terrible online reputation once you got past the new company he's formed.

I know more about solid stone walls, but the bit that concerns me is the repointing and the paint.

Have you done the pointing in cement? If so that is the likely cause of the damp. Cement is way more waterproof than stone and some older style bricks. This means it will slowly evaporate through the bricks, but get caught by the paint.

This all depends on how old your property is. If it's pre world wars then it'll be built using lime pointing.

There's a few options,

- Get in touch with a builder who specialises in older properties

- Remove the paint and hope this is enough 

- Remove the cement pointing and repoint in lime

Thanks.  We didn't do either the pointing bor the painting but I think it's lime