insulating solid walls.

[tony]

Hi,
New member so be gentle.

I have a semit detached villa built in whinstone, walls about 800mm thick( i know this be3cause it took 15 hrs to core a hole for the boiler flue).
Renovating house 1 room at a time.
Now in Lounge, bay window beyond repair(house empty for years) dry rot wet rot woodworm mice .
Getting new timber sash and case windows made by local joiner,below window is cladding to the floor, i was sanding the floor and paying more attention to the construction i noted that this cladding would have to come off for the windows to come out and then replace cladding.
I am handy with the tools so i carefully removed cladding( found wood worm, and sprayed all wood in area.

Now Behind the cladding is the stone walls, would it be possible to fit insulation to this wall directly or is a gap required.
from wall to rear of cladding 50mm max.

Best Regards

Tony

 

[GK]

There's a good chance you'll get condensation on the cold side of the insulation so you need to arrange for a gap and ventilation to carry it away

 

[MdB]

I have a similar problem to Tony so thought I would add to this thread to see if someone can answer us both.

My house has end walls which are 1850ish stone rubble construction whilst the rest of the house is 1970 solid block construction. It suffers slightly from damp but the main issue is heat loss.

The front wall (supports roof) is only 150mm wide and the plan is to add an extra layer of block work to add strength and to create a cavity to improve insulation.

The back walls are 250mm block and don't need to be strengthened but could really do with added insulation. I was thinking of battens + small cavity + insulation + plaster board. Maybe 50mm total thickness. Would this be a good idea or would ventilation be required (not sure how this would be done)?

The end walls are lime plastered on the inside which is soft and damp especially inside a built in cupboard due to lack of ventilation (plan to remove this). The battens + small cavity + insulation + plasterboard for this wall worries me due to the likelihood of condensation occurring in the cavity. Ventilation though would defeat the insulation though (I would assume) so wouldn't gain me much.

Any good suggestions?

 

[GK]

Can you knock through for four airbricks, one in each corner of your block wall? Then you need to fix battens somehow leaving a cross flow airpath and fix insulation over them. I've used semi rigid insulation board and then fix a vapour barrier over it all before reed and lime plaster.

Ventilating the gap to the outside won't affect the performance of the insulation

 

[GK]

Here's my dry lined wall. The frame is fixed to the floor and the ceiling joists only, but with a few packers at shoulder height to brace against the brickwork. The packers have a small piece of dpc material behind them. See how the frame follows the wonky wall. Insulation is 75mm thick and the gap is about 40mm or so. Varies a bit.

The room above has the same treatment. At ground floor level, shown, the floorboards were decayed at the ends leaving a useful path to the underfloor void, which is ventilated. At first floor level, the new floorboards have multiple holes drilled in the ends.

So - there is a continuous ventilation gap from the underfloor void area at ground floor to the attic space which is very draughty. This isn't a breathing structure, generally advocated for old properties, but I've dealt with it in a different way.

This is what it looks like much later with lath and lime plaster to the ceiling, vapour barrier over the insulation board (not visible), thin plywood holds the vapour barrier in place and serves as a fixing background for the reed mat.
The wall shown and the ceiling has one coat of lime plaster.

This room hasn't got quite the same feel as the rooms that have lime plaster applied to the masonry - or does it? Most people are fooled until they tap the wall. Maybe it's just that I know what's there..

And when the house becomes a museum or energy becomes free the whole lot can be dismantled and there'll almost be no trace of it