'Localised' re-rendering?

[Gerry555]

We've got a couple of internal damp patches due to penetrating damp - the result of cracked, external render. We're thinking of having the render chipped away only where the problems are. The new scratch & finishing coats will be waterproof, but do you foresee any problem in the long term? Or does the whole wall have to be done to make everything waterproof?

Apologies is this question seems a bit naive, but I really am clueless. Don't worry, we're going to get builders in to do the work, but I just wanted some impartial advice (the cost of having the existing render totally removed is astronomical, so we'd rather just patch things up).

 

[Micilin]

First make sure you find the source of damp.this needs addressing first.
Second get at least 3 people in to look at it to quote and ask to look at previous work.

Third, afraid just doing patches is probably not the way forward but hard to tell without inspection

Finally- pictures?

 

[joe-90]

Most houses have no render and no damp. Why is that?

 

[Gerry555]

Most houses have no render and no damp. Why is that?

I know, but unfortunately the property was rendered in the 70s to cover-up the scars of some rather bizarre alterations. Also, the cost of having the render removed is astronomical, so we're stuck with it.

There's no point posting pics, because there's nothing to see other than a few cracks in the render (which was probably never weather proof in the first place). A surveyor from a damp-proof company told us off-the- record, that the problem is due to penetrating damp. His company only do internal damp-proofing so this diagnosis was impartial (he effectively did himself out of a job). We also suspected that the problem was due to penetrating damp.

Obviously, once the builders chip away the old render, if there are any cracks etc, they'll need addressing. However, once new render is applied, will it be undermined by the fact that the old stuff is duff? All we're trying to do is stop ingress directly where the problems are.

 

[joe-90]

The only place I've ever seen penetrating damp is on the coast where the rain comes sideways. Where are your chimney breasts and is the roof in good nick?

 

[Gerry555]

The only place I've ever seen penetrating damp is on the coast where the rain comes sideways. Where are your chimney breasts and is the roof in good nick?

Both patches are near to windows. The render has failed either side of said windows. Exactly the other side of the damp patches, the render is cracked. It is retaining moisture after it rains (it's damp to the touch for the next day or two). Presumably the pointing is dodgy under the render...or there's possible damage to brickwork. Either way, there's water ingress: damp patches a foot in diameter, half way up the wall, and not coming up from the base via absorbent plaster).

The surveyor reckoned it's penetrating damp, which is what we suspected all along (dehumidifier does bugger all and the wall is only damp after rainfall).