Hi
Looking for some insulation advice on my restoration/renovation project. The house single story and in two sections.

One - 2 room 200 yr old rubble stone with uninsulated suspended wooden floors . No damp proof membrane under floors or silicone injection in walls. Wall s are framed and plaster boarded so that there is an air gap between stone work and plasterboard. Platerboard is largley knackered. Some damp under floor (most likey due to poor drainage and guttering - will sort that out). Plan is to rip out floors and plasterboard (on external walls). Floors will then be replaced - damp proof membrane, screed, insulation, ufh, more screed then tiles/stone. Walls - insulate then plasterboard. Cant externally insulate stone part due to planning restrictions.

two. 1940s-50s brick with cavity (could insulate cavity but have heard horror stories) , concrete floor with no dampproof membrane. Walls have a broken down bitumen "DPC" and are rendered with pabbledash to ground level. Some damp at bottom of walls (condensation?) but cold and bloody draughty around electrical sockets (must go into cavity). Plan to insulate external walls (not sure how), take down internal walls, dampproof membrane on top of existing floor (there is plenty of headroom) then insulate, ufh ,screed and engineered wood or tile. New walls to go on top of dpc.

There will be a sizable timber framed /clad extension that will be heavily insulated with pavaclad and hemp that will make some of the existing external walls internal.

Generally I would like to cut down on draughts in the older parts but keep the insulation breathable if possible /economically practical.

My questions:

1. How do I avoid damp/condensation issues in the old stone walls after insulation especially as there will no longer be a suspended floor to allow airflow up the gap between wall and plasterboard. I cant be sure how well the extisitng wall prevents penetration of wind driven rain as old age and mice will have meant that there will be big gaps in the lime mortar/ earth between the stones in the centre of the wall. Is it best to redo the framing and insulate then clad with plasterboard or is there any sense in rendering the inside of the wall and cladding with inulation ?(have just found something called pavadentro at http://www.natural-building.co.uk/pavadentro_renovation.htm which might be usefull.)

2. Insulating the brick walls - inside or outside? and what with?

3. Is it worth doing a silicone injection in the walls? I dont have a mortgage and dont plan to sell but who knows in the future? Very suspicious about silicone in old stone walls as our local stone is not at all porous. The birck walls are another issue and it might be much cheaper than trying to retro fit an effective dpc in the walls. The pavadentro internal insulation must be above the dpc . External ground level and floor level are pretty much the same.

Any comments much welcomed.

Jay

Whoops, wrong button.

Suggestions, order still random

3. Damp treatment. I've tried various methods and found that injection is unreliable in random stone walls. Similarly the cementatious compound was very unreliable. The electro-osmotic system worked for us but it was still was not 100% perfect, a few minor problems around chimney breasts. Internal cement based tanking was also unreliable but I found stud membrane worked well but that one was a brick building.

1. Stone walls are not remotely windproof, I'd render the inner face first with water resisting additive.

2. The brick bit. I've not installed external insulation myself but it is considered technically superior. The advocates make light of the changes to eaves, verges, window and door openings, drainage, services. They ignore the fact that the industry in this country is a carefully controlled sector and the price charged is high, 2x to 3x the price in Germany (Housing Corporation, Fit for the Future 2, p37, 2008). I've considered it myself seriously but the only building where it would have been suitable was ruled out absolutely by the planning department. If you are refurbishing the inside, my guess is that you'll insulate internally and I'd suggest the lightweight steel stud system over a continous and sealed layer of insulation.

Fred

Both Gervases and Freds comments are very useful -thanks. I am wary about using modern solutions on old walls and could spend the money more usefully else where (drainage etc).

I have just found out the price of pavadentro and the fact that, for it to breathe, it needs to have a lime based render between it and the wall and all traces of gypsum and cement removed. Very expensive!

My current line of thought on the stone bit is to frame the walls with an air gap and insulate with sheeps wool before covering with plasterboard. To avoid moisture collecting at the bottom of the wall I am considering some vents in the skirting board. It does mean i will be creating a source of draughts but that seems better than mold and rot! I was thinking (hoping) that the ufh will help create a bit of circulation in the gap to move air about and help keep things dry.

As for the brick section - Ive looked at the external surface and reckon that it would be expensive and difficult to insulate as the roof will need extending out to cover the extra thickness.

If I am to clad the inside with insulation what size of gap do I need to leave between the existing wall and the new insulation/ plasterboard?

Jamie

The best solution for the rubble stone is to repoint the outside with lime mortar. Strip the internal face back to stone removing all render etc and insulate with hemp&lime mix shuttered directly up against the wall in a timber frame, finished with lime render. I'd have a poke about on this website where there are lots of pictures:-

http://www.oldbuilders.com/indexmainpage.htm

You could do the same with the brick.