Cladding and wainscoting of cold internal walls

gutovicky

Agreed FreeBear, I'd definitely include the reveals if I was insulating that window-wall.

There's one question that got missed early on, that I need to flag it up again:
When insulating a wall with layers of foil-faced Celotex/Kingspan and timber battens, as you first described to me, is it OK to do this to a wall that's still rendered/plastered - not bare brick?!

The rendered & plastered surface is perfectly smooth & sound btw.

Cheers, Vicky

chris_n

You would be better off doing half as much insulation on both walls if cost is the problem. The first insulation you do is the most cost effective, making it thicker improves it but it is diminishing returns. You can insulate on to sound plaster no problem. If you have electric sockets on the walls be careful with the detailing in that area so you don't leave a cold spot behind and don't get normal spray foam on your wiring.

FreeBear

gutovicky said: There's one question that got missed early on, that I need to flag it up again:
When insulating a wall with layers of foil-faced Celotex/Kingspan and timber battens, as you first described to me, is it OK to do this to a wall that's still rendered/plastered - not bare brick?!

Once your skirting boards and any picture rail & coving is off, you can fix straight on to the plastered wall(s). Taking the plaster off is only really needed if you need to eek out every spare inch of floor space.

[Deleted User]

Excellent thread @gutovicky , i'm learning from you, and @FreeBear with this.
As i said in another thread, this member is one of the ones that has a mass of information and advice behind them 😊👍

gutovicky

So, I CAN insulate against sound render/plaster - that's a relief!!    Thank you chris_n & FreeBear.

And good heads-up chris_n, re: managing an electric socket & taking care when spray-foaming near wiring.
I DO have a socket to sort out as part of this project. However, I was thinking of relocating this entirely - to elsewhere within the room.
I would just detach the socket's wiring from the relevant junction box in the loft-space and leave the redundant wiring in the wall - I presume that's not an issue?
Chasing-in new wiring for a new socket elsewhere in the room will be messy of course - but it's about time I learnt how to do this since, over time, there are other sockets I'd like to relocate in the property!

I'm absolutely with you there Catsacor!!  
This Forum is such a fantastic resource - particularly as the cost of living soars. 
For this current project, FreeBear has explained a useful methodology.  But, just as important, using clear and accessible language (& photos), he's provided me with the CONFIDENCE to forge ahead & have-a-go!  
I'm very grateful, and the fact that the thread may be helping/inspiring others is a big bonus.

Best wishes, Vicky

plumb1_2

Maybe someone can educate me, why not just foam fix insulated plasterboard to the wall, tape and fill joints. Why use timber batterns 

FreeBear

gutovicky said: I DO have a socket to sort out as part of this project. However, I was thinking of relocating this entirely - to elsewhere within the room.
I would just detach the socket's wiring from the relevant junction box in the loft-space and leave the redundant wiring in the wall - I presume that's not an issue?
Chasing-in new wiring for a new socket elsewhere in the room will be messy of course - but it's about time I learnt how to do this since, over time, there are other sockets I'd like to relocate in the property!

One doesn't normally have junction boxes in the loft for the ring main. The "standard" way of doing it is to run a pair of 2.5mm² cables from one socket to the next (sometimes, it is 4mm² for a radial main). Depending on who and when the wiring was done, the cables may be clipped to the wall, covered with a thin steel capping, and then plastered over - A pig to pull the cables out.... If the sockets were put in at a later date, surface mounted trunking could have been used - Piggin ugly, but much easier to move things around.

If you want sockets (or switches) on the wall(s) you are insulating, it is worth putting some thought in to where you want these items located before starting work. Put up your first layer or two of Celotex, and before the last 25mm layer goes on, fix some 35mm deep back boxes to the wall - The screws can go right through the insulation in to solid brick (two per back box). Run some 20mm conduit straight up the wall using some tape to hold it in place temporarily. Fix your final layer of 25mm Celotex either side of the conduit and fill the gap with expanding foam. When fully cured, cut back flush with the surface and then cover with alumininium foil tape.

The back box will be protruding ~12mm from the surface which will be just about right when the plasterboard or timber cladding goes on. If you decide to fix plasterboard & skim at any time, cover the lugs inside the back boxes with a bit of masking tape and cut a piece of cardboard to be a snug fit in the box. Plaster will get everywhere gum up the screw holes if you don't mask things off.

plumb1_2 said:

Maybe someone can educate me, why not just foam fix insulated plasterboard to the wall, tape and fill joints. Why use timber batterns 

If you are using insulated plasterboard, it can be stuck to the wall with a suitable adhesive. Mechanical fixings are still advisable though... Individual sheets of Celotex/Kingspan (plus plasterboard) can work out a little cheaper. Having battens fixed to the wall gives you somewhere to attach heavier loads such as curtain rails/poles. And if you use 12mm plywood in place of plasterboard, small cupboards & shelves can be screwed to the wall without having to go through a thick layer of insulation.

Last reason - a 2.4m x 1.2m sheet of insulated plasterboard is quite heavy and not easy to handle if you're working alone (even worse if you have to get it up a narrow flight of stairs). Celotex/Kingspan sheets weigh very little, and 1.8m x 0.9m sheets of plasterboard are much easier to move around - You also have a choice as to the type of material to use for the finished surface. Plasterboard, cement board & tiled, or timber.

plumb1_2

Yes I agree full boards are a little heavy, but can be cut down to manageable size if your planning on skimming them.

FreeBear

plumb1_2 said:

Yes I agree full boards are a little heavy, but can be cut down to manageable size if your planning on skimming them.

The OP is planning on using timber cladding. If she is also fixing sockets to the wall, multiple layers of Celotex makes it easier to bury the conduit & back boxes. Another added advantage is you get get multiple layers of a vapour control membrane (the foil facing) for free.

FreeBear

FreeBear said: If you want sockets (or switches) on the wall(s) you are insulating, it is worth putting some thought in to where you want these items located before starting work. Put up your first layer or two of Celotex, and before the last 25mm layer goes on, fix some 35mm deep back boxes to the wall

A picture....

Just roughly set up using some scraps of material to demonstrate the idea. For extra strength, the back box could be screwed to the batten as well as a couple of screws through the back.

Tip - A serrated kitchen knife is an ideal tool for cutting the insulation. A clean cut with minimal dust. I have a Kitchen Devil about 150mm long that I use.