Patching stone wall on an 1850's house

[philpowell]

Hi all — first post here.

We've just bought our first little "project" house, which we're in the process of renovating. It's a strurdy 1850's terrace and the exterior walls are in-filled stone and in pretty good condition. We've had quite a few experts check the damp situation, and we're lucky in that there's no sign of any major damp problems, which is a relief.

As I've started to strip back the layers of wallpaper and paint, and after chasing out for new electrics, it appears that there are quite a lot of patches of plaster which are blown and crumbling away. The interior walls aren't a problem, as they are brick-built — but I'm trying to work out the best course of action for repairing the patches on the exterior and party walls.

A lot of what I've read about stone-built buildings suggest that lime render is the logical way to go, to allow the walls to breathe properly. But I can't find much to suggest whether or not it's safe to use gypsum plaster or not.

My original thinking was to patch the exposed areas using a base of bonding plaster, and then apply a finishing coat of multi-finish plaster, but I'm a bit wary about doing that if it's going to cause problems with moisture.

Any advice from anyone who's had to do anything similar would be much appreciated.

 

[peaps]

Hi all — first post here.

We've just bought our first little "project" house, which we're in the process of renovating. It's a strurdy 1850's terrace and the exterior walls are in-filled stone and in pretty good condition. We've had quite a few experts check the damp situation, and we're lucky in that there's no sign of any major damp problems, which is a relief.

As I've started to strip back the layers of wallpaper and paint, and after chasing out for new electrics, it appears that there are quite a lot of patches of plaster which are blown and crumbling away. The interior walls aren't a problem, as they are brick-built — but I'm trying to work out the best course of action for repairing the patches on the exterior and party walls.

A lot of what I've read about stone-built buildings suggest that lime render is the logical way to go, to allow the walls to breathe properly. But I can't find much to suggest whether or not it's safe to use gypsum plaster or not.

My original thinking was to patch the exposed areas using a base of bonding plaster, and then apply a finishing coat of multi-finish plaster, but I'm a bit wary about doing that if it's going to cause problems with moisture.

Any advice from anyone who's had to do anything similar would be much appreciated.

You need to mix up some lime render using NHL 3.5 and a good quality clean sharp sand. Take care to use clean water and don't put too much water in as it causes problems with shrinkage. Clean down the area making sure all the dust is removed and wet down the wall until you can see water run freely down the wall when you slash it. Apply the lime mix in layers of 8/10mm leaving time for each coat to dry, you may not need to build up the float coat as this will depend on how true the wall is.

You should keep an eye on the float coat when it's drying out and mist spray if needed. Don't worry about small airline crack as these will "repair" themselves in the cure process.

Finish coat will be NHL 3.5 and a good clean fine sand.

Mixes depend on situation, lime used and the quality of the lime.

This link may help

http://www.jjsharpe.co.uk/material.html

 

[Possel]

A lot of what I've read about stone-built buildings suggest that lime render is the logical way to go, to allow the walls to breathe properly. But I can't find much to suggest whether or not it's safe to use gypsum plaster or not.

In a word, don't. Anything gypsum based is not compatible with lime mortar and will indeed prevent the wall from breathing, which is especially important on the external and party walls. Vinyl paints and wallpaper have the similar effect as well. If you don't let it all breathe, you start chasing the dampness around rather than letting it evaporate naturally as intended.

Google for "lime mortar" + dampness and study what you get (but ignore the DPC companies!) if you want to know how best to look after your old house. See my blog http://houseintheenchantedforest.blogspot.com/ which tells how I have a dry warm property of a similar age and construction without using gypsum or cement, except in a bit of new build.