Rising damp?

[Geno]

Firstly I must congratulate you on a great site with lots of very useful information.

We've recently moved in to an old (1840s) house, which had been extensively modernised by previous owners. Or intention to take the property back to some of it's former glory has revealed problems with damp. This is mostly evident on external walls to a height of about 1 foot. However, there are also patches on internal walls, again to about a foot from the floor (solid). I'm not sure wether the dampness is due to rising or penetrating damp. The external walls have patio/driveway to floor level so it could be that bridging is a problem. At this stage, I'd prefer not to lower the patio or driveway, but may consider chasing out a channel adjacent to the house and filling with gravel.

My initial thoughts regarding a solution would involve removing plaster from walls, removing rubble build up from the cavity then allowing the walls to dry before applying mortar and finishing with lime plaster. Also, repairing cracked mortar at ground level.

Does this sound like a reasonable approach. Any useful tips would be greatly appreciated.

Thanks,

Geno

 

[Gervase]

It certainly sounds as though the raised levels outside are affecting the inside. Is it possible to dig a channel down to a level below the current internal floor level, as that's what you'd need to do, and ideally then install a perforated land drain with a fall to a sump or soakaway to take the water away from the house.
In most cases damp can be cured by adequate drainage, so once the walls are dry, the lime approach should help them stay that way.

 

[NT]

quote Geno

>problems with damp. This is mostly evident on external walls to a height of about 1 foot. However, there are also patches on internal walls, again to about a foot from the floor (solid). I'm not sure wether the dampness is due to rising or penetrating damp.

Rising damp does exist, but is rare, and is not worth addressing unless you've tried every other damp repair trick in the book, and are still gettting damp.

Penetrating wont be the problem on your inside walls, but it is likely on the exterior ones. Lowering the ground close to the wall should help a lot.


> The external walls have patio/driveway to floor level so it could be that bridging is a problem.

I wouldnt expect there would be anything to bridge.


> At this stage, I'd prefer not to lower the patio or driveway, but may consider chasing out a channel adjacent to the house and filling with gravel.

yes, at a lower level.


> My initial thoughts regarding a solution would involve removing plaster from walls, removing rubble build up from the cavity then allowing the walls to dry before applying mortar and finishing with lime plaster.

If you did manage that, I dont see what it would achieve. I dont know how you'd remove rubble from the cavity either, if your walls are cavity. You'd have to knock holes in the wall to do it, or fish stuff out from the loft - neither would be a good plan imho.


>Also, repairing cracked mortar at ground level.

yes, using lime not cement. Cement pointing traps damp, lime evaporates it.


NT

 

[Geno]

Thanks for the suggestions.

I've now chased out the plaster from the affected areas, and the underlying brick is starting to dry out. Next, as you say, is to dig out a channel and fill to a lower level with gravel. Rather conveniently, there's a drain located nearby which I can divert to. I exepct that this will be enough to solve the external walls, but I'm still at a loss as to what to do about the patch on the internal wall, especially as it's a shared wall to the adjoining property. I suspect that the damp here is due to condensation as it's just an isolated patch. I'm in the process of fitting a log burner on the same wall. Will this help if the problem is due to condensation, as the bricks should act as a heat sink?

Cheers,

Geno

 

[NT]

I'd agree condensation is most likely, unless your neighbours are upto something strange. Sorting out the other damp patches will reduce the RH in the house, and this will reduce condensation. It may clear on its own. If not, maybe time to look at other sources of damp in teh building, and take action to reduce them. Usual things like roof slates, lead valleys, overflowing or rusted through gutters, damaged or blocked downpipes, check the paths slope away from the house, around windows and so on.

Breathable finishes also help with evaporation of damp walls. Distemper rather than emulsion on your affected areas. Unless of course you're affected with distemper, then you'd need some kind of emulsion for that.

Hopefully you dont have any impermeable finishes on the exterior.


NT