Rain Penetration after repointing - bad weather or wrong mortar?

[bfgjohno]

We had the 1750's house's gable end of rubble-filled solid stone walls repointed last year. The mortar used was cement/lime/sand. The chimney stack was rebuilt. At the same time chimneys were relined - two with SS liners and one with clay pipe. The areas inside that needed replastering after breaking into the chimney flues were replastered with "good old" gypsum onto the stone. Lime plaster we think lies on each side of the gypsum areas. Guttering seems fine and roof space is dry. Damp/wet areas of internal walls match exposed areas of external wall - we are semi-detached to a lower house and the external wall protected by their roof and rooms is not effected.

The wall faces into the prevailing wind which has been laden with rain for the past few weeks. We rapidly noticed that the plaster inside was lifting off the wall, cracking, squelching and water dribbling. Areas which didn't lift have become damp and mouldy. Paint has blistered. The gypsum plaster seems to remain intact - just darkens with damp.

Is this just what happens in solid walled houses in horrendous driven rain or will the cement/lime/sand mortar have played a part? Would the house benefit from a thick lime render on that side? Should we hack out and repoint again with lime mortar? Should we replace internal gypsum with lime plaster?

Thoughts most gratefully received! :?

 

[malcolm]

Until you get to 5 posts there is a delay in your posts appearing and we miss them. The way around that is to post links to pictures and then some more pictures!

You mentioned you were in the Yorkshire dales. My cousin in Sheffield has a barn built in soft sandstone which didn't take kindly to cement re-pointing - the stones on one wall have spalled very badly. But it is very common up there to see stone finished buildings so it must be possible to get them to work. Nobody likes to live in damp houses and they would all be rendered if the problem was not possible to resolve.

My only experience of damp through a stone wall as in a rental house. We tracked the problem to cracks between the cement pointing and the stone. Water would drip from above a window when the rain was blown from a certain direction. We didn't fix the problem because it was a rented house, and of course the landlord didn't fix it.

Do post some photos in at least two posts.

 

[MatthewC]

We had the 1750's house's gable end of rubble-filled solid stone walls repointed last year. The mortar used was cement/lime/sand.

"Cement/lime/sand"? Probably "hydrated lime"? A mixture beloved of many modern builders because they pretend that it's sympathetic to lime-built buildings, but in fact the cement will make the lime content ineffective as regards breathablility. What the hydrated lime does for them is to improve the workability of the mix; most of us would have used NHL3.5 with sand (3 sand :1 NHL by volume).

It sounds as though water is able to get in somewhere and, once inside the wall, cannot escape because of the impervious cement pointing. I'm sure you had the flashing around the roof/chimney join re-done, and that the chimney has some sort of cap so that water cannot get down it. What sort of stone is it? How deep was the re-pointing?

There's definitely no value in re-plastering anything until the source of the damp issue is sorted.