Nemesis's words in the current repointing thread - ("No - NO CEMENT AT ALL! It could ruin the wall in the short or long term")
have prompted me to share this interesting problem, and I would like to know what other members think we should do.
Our extension project is progressing well - it consists of building a new room on top of the existing single storey kitchen which projects from the end gable wall of our house. The main house is perhaps originally eighteenth century, but with 19th and 20th century additions and alterations, and the kitchen is almost certainly a 19th century addition, built in traditional style with rubble limestone walls, though there has been one much newer window added. The house is not listed.
The extension will be, at least at the back, more modern in style with a big south-facing window, though it is intended to be in keeping with the rest of the house, and will re-use original slates as well as one of the old chimney pots on the new wood-stove chimney which will replace the tall old chimney whose stone stack was built up almost to the height of the main house roof. The new build is cavity-wall concrete block (not very eco I know - sorry) built up on a concrete ring cast around the top of the old thick rubble limestone walls of the kitchen. So - lots of cement, BUT the whole will be lime rendered, replacing the cement & pebble-dash render which previously covered the old walls and has now been hacked off. The theory behind this is all the usual arguments about allowing the old kitchen walls to breathe (even though, alas they are mostly lined with a hard cement render/plaster on the inside) - and also blending the new work in with the old, and discouraging any tendency for cracks to develop between the two.
Now - the upper half of the old house gable end wall was formerly external, and will soon be internal. It was covered in the same cement-render pebbledash. Below this, in the space between the old kitchen ceiling and roof, there was a triangle of crumbling old lime plaster. At the bottom, inside the kitchen, there is modern (1950) cement render, which it is far too much trouble to remove. The whole of the rest of the wall is now stripped of render and is now revealed as thick, random limestone rubble and stones with odd bits of brick stuck into it, big holes where the kitchen roof purlins went. It has three flues rising through it, one unused, and two lined with the CICO method - for which we were responsible about fifteen years ago (and yes I know it's not considered kosher now).
Supported by our architect (and by the builder, who is experienced in conservation lime-work) we are specifying solid lime repointing and rendering for this wall, now it is to become one of the internal walls of the new room. There has been damp in it for years from the old unused flue, and I want to allow for movement, and for it to be a heat store both for the solar gain into the new room and also from the aga which is against it at the bottom. I hope experts here agree. We certainly didn't want to do what would have been the more conventional and much cheaper option of just covering it with insulated board.
BUT - the steel ridge girder has to be supported on a concrete pad, set into the old wall with cement mortar, for strength. There will be a doorway made through into the old house, right on the corner, so some new blockwork will be required on one side of it - with cement mortar supporting the steel lintel and support structure around it. On INSIDE face of the old wall there has been quite a lot of filling with cement over the years up in the roof space and also lower down in the bedroom, where there is a big patch of gypsum plaster.
Also, the other walls inside the new room will be skimmed insulated plasterboard, except for the one which will be mostly glass, and the narrow chimney-breast which will also be solid lime plaster (over concrete block).
So - am I being too purist in wanting all this time-consuming and expensive lime-work? Am I mad, too influenced by all the lime enthusiasts on this forum and elsewhere? Does all the concrete completely compromise any conservation or eco-credentials maybe gained elsewhere?
Incidentally, the builder is completely supportive - but perhaps he's just being polite!
What would other Forum members do in this case?
have prompted me to share this interesting problem, and I would like to know what other members think we should do.
Our extension project is progressing well - it consists of building a new room on top of the existing single storey kitchen which projects from the end gable wall of our house. The main house is perhaps originally eighteenth century, but with 19th and 20th century additions and alterations, and the kitchen is almost certainly a 19th century addition, built in traditional style with rubble limestone walls, though there has been one much newer window added. The house is not listed.
The extension will be, at least at the back, more modern in style with a big south-facing window, though it is intended to be in keeping with the rest of the house, and will re-use original slates as well as one of the old chimney pots on the new wood-stove chimney which will replace the tall old chimney whose stone stack was built up almost to the height of the main house roof. The new build is cavity-wall concrete block (not very eco I know - sorry) built up on a concrete ring cast around the top of the old thick rubble limestone walls of the kitchen. So - lots of cement, BUT the whole will be lime rendered, replacing the cement & pebble-dash render which previously covered the old walls and has now been hacked off. The theory behind this is all the usual arguments about allowing the old kitchen walls to breathe (even though, alas they are mostly lined with a hard cement render/plaster on the inside) - and also blending the new work in with the old, and discouraging any tendency for cracks to develop between the two.
Now - the upper half of the old house gable end wall was formerly external, and will soon be internal. It was covered in the same cement-render pebbledash. Below this, in the space between the old kitchen ceiling and roof, there was a triangle of crumbling old lime plaster. At the bottom, inside the kitchen, there is modern (1950) cement render, which it is far too much trouble to remove. The whole of the rest of the wall is now stripped of render and is now revealed as thick, random limestone rubble and stones with odd bits of brick stuck into it, big holes where the kitchen roof purlins went. It has three flues rising through it, one unused, and two lined with the CICO method - for which we were responsible about fifteen years ago (and yes I know it's not considered kosher now).
Supported by our architect (and by the builder, who is experienced in conservation lime-work) we are specifying solid lime repointing and rendering for this wall, now it is to become one of the internal walls of the new room. There has been damp in it for years from the old unused flue, and I want to allow for movement, and for it to be a heat store both for the solar gain into the new room and also from the aga which is against it at the bottom. I hope experts here agree. We certainly didn't want to do what would have been the more conventional and much cheaper option of just covering it with insulated board.
BUT - the steel ridge girder has to be supported on a concrete pad, set into the old wall with cement mortar, for strength. There will be a doorway made through into the old house, right on the corner, so some new blockwork will be required on one side of it - with cement mortar supporting the steel lintel and support structure around it. On INSIDE face of the old wall there has been quite a lot of filling with cement over the years up in the roof space and also lower down in the bedroom, where there is a big patch of gypsum plaster.
Also, the other walls inside the new room will be skimmed insulated plasterboard, except for the one which will be mostly glass, and the narrow chimney-breast which will also be solid lime plaster (over concrete block).
So - am I being too purist in wanting all this time-consuming and expensive lime-work? Am I mad, too influenced by all the lime enthusiasts on this forum and elsewhere? Does all the concrete completely compromise any conservation or eco-credentials maybe gained elsewhere?
Incidentally, the builder is completely supportive - but perhaps he's just being polite!
What would other Forum members do in this case?
