Internal insulation of Bathroom

[rhys]

Air gap-  yes Wookey there must be no air circulation - quite right - needs a seal all around the perimeter.Your foam method is best.
Dot and Dab is not recomended for fixing insulation. Use  a continuous bead - all as Kingspan and others instructions.
Yes on balance I think a separate air/vapour barrier or foil taping is the better option. For DIY the extra labour is offset by material costs.
The method you describe is the way I have done it here but with laminated boards and lots and lots of Fire rated foam !!! Top,  bottom AND between boards before taping and jointing- this avoids the possible air path between boards, no worse than at the edges with expanding foam.
I am concerned that Kingspan have removed this method ( for solid walls)
from their advice sheets. Suspect it because of the wobbly and damp wall issues.
Still recommended by the EST.
Mechanical fixingws are essential - to hold the boards in place in the event of fire, this is also another very good reason to make sure there is no air path from the room to behind the boards.

[wookey]

I know the mech fixings are recommended everywhere for the reason you give, but given that the plasterboard is the fireproof layer which should prevent anything behind it getting over 100C until all the anhydrous water has been removed it's going to be quite a while before the PU melts and to be honest if you are trying to get out by that route after the PU has melted and the boards fallen off the wall you've probably already died of smoke inhalation some time ago.

I note that the PU glue is 'B2 fire rated'. Despite reading the spec I found it hard to determine what this means but it presumably means that it'll continue holding the boards on for a while during a fire?

Mech fixings through the boards make holes in the vapour layer, add thermal bridges and require decoration, so there is aquite a lot to be said for avoiding them. I'd certainly go for ~2 per board these days, not the 9 recommended in most docs (instructions I followed in previous house).

So, convince me that glued-only boards really are a fire risk...

[Stuart]

Had the plaster round on friday to have a look and he said to use thermal laminate boards. been doing loads of product research and found the following products which i may as well list as it may well save someone some time!

these are the ones with vapour checks, as it will be a bathroom on a cold north masonry wall.

Kingspan k17, not the thinest
Lafarge GTEC thermal board k
Knauf thermal laminate with vapour check
Gyproc thermal Line super

Unfortunately unless i wanted a pallet of 20  the only ones all the major boys stocked was the gyproc product which, seems to be about £30 a sheet for 40mm.

finally got to a decent local builders merchant, who asked what i was after doing. he then surgested buying the insulation and plaster board separate, and doing it as Wookey surgested. Was really hoping to do it with 40mm insulation as space will be a problem, he recomended 50mm but said i could double up some 20mm as they didnt do 40mm and then he found they had some returned 20mm board which i could have for £4 a sheet , he recommended 4 hammer fixings per sheet to hold it.
So looks like I'll be just getting the plaster to do the skim!

[Greenbeast]

cool

i've still not decided how i'm going to do it and i suspect its a way off with finances as they are.
I'm only interested in getting my new boiler in and replacing the bathroom ceiling before next winter!

[wookey]

The cost for 80mm thinkness for one room with 6linear metres of wall is about £230. 5 x 80mm PUR, 5 plasterboard sheets, foil tape, can of multi-stik/gripfix, couple of cans of foam, 25mm PUR for reveals, tescon tape for joists and window surrounds. In practice there is probably a load of plumbing to change around too which adds to the costs. i.e it's labour-intensive but not expensive.

[Stuart]

Just a couple of pics of my ongoing doing it cheap project.

1. £4 of 20mm insulation board (from a site return, packing was soiled slightly and a few holes in one sheet, rest were fine)

2. £1.70 use Half a tube of pink grip (tipically too long for a standard gun, good job its cardboard)

3. £4.60 9.5mm tapered plasterboard.

so that works out at £9.45 a sheet to make yourself, the important thing to note is the that the commercial laminated plasterboard only start to include fancy things like vapour checks and better than polystyrene insulation when they get to £28 a sheet or so.
saying that had a look round the builders merchant and found a pile of damaged thermalline supper, which I'm sure they would be wanting rid of.
4. went to get some of that insta-fix, not a bad price until you figure in the price of the applicator gun that it needs, so decided to try normal PU foam as i had bought a box of 12 cheap.
i moistened up the wall a little to help it set faster. and it was cured after 20min, so plenty time to adjust the levels. seems to have stuck VERY well.

will let you know how we get on!

[dhaslam]

Why not use  more insulation?   Because the wall in north facing  it is always going to be cold, even in summer.

[Stuart]

2 layers of 20mm and plasterboard is all i can afford space wise as its getting tiled too 

TBH cleaning the loose debris from around the windows and sealing them up with PU foam has made a big difference already.

[JohnS]

At Ecobuild, Knauf was showing their internal wall insulation system.

http://www.knaufinsulation.co.uk/pdf/Case%20Study%20-%20Low%20Energy%20Whole%20House%20Refurbishment%20RBU120009.pdf

Basically it was XPS with bonded OSB to act as studs and screwed to the walls with Ecosse glassfibre wool between.  The studs were sealed to the walls with filler.  No air gap was needed as neither would be effected by damp as XPS is closed cell and the glass is treated.  Plasterboard was then fixed to the studs. 

John

[desperate]

Hi Stuart,

I am being daft now, but ,       

you show your insulation boards and the pink grip and the plasterboard being stuck on yes? then on the wall with the window, just the bare insulation board, what happened to the PBd?? have I missed something

Desp

[Stuart]

Desp probably wasn't clear, 20mm insulation on the walls, then add my 20mm homebrew laminate.

[Stuart]

its skimmed now, those hammer fixings show through when drying so there must be a bit of thermal bridging.
The foam sticks to boards on so well don't really need the hammer fixings, although in my case they helped pull the boards true on my 1850's brickwork.

warm as toast in there now! highly recomended. Have some more pics perhaps we can make a how to thread?

[MR GUS]

just before I went away I could have sworn I saw a big name in foam board insulation now selling a foam board slapped onto hardiebacker type product for use inside & out...
cannot find it to date, however i'd like to find it / bodge some to building controls satisfaction in order to open up a front aspect to light & as an entrypoint whilst being able to quickly (well an hour or so) fix it on to retain heat in the colder seasons either partially or fully (a-la barn door).

[Greenbeast]

Ok i'm actually at the point of starting this project now.

The walls are brick only (no plaster) and probably not particular level.

Currently i'm thinking about 2x1" horizontal battens and then vertical battens with kingspan/celotex in between.
This way i can even out the walls and also save on insulation (for a given thickness of battening)

Not sure what depth of insulation yet, we're sort of restricted in one direction (need to fit a reasonable bath in) but not so much in the other, so the depth may be different on different walls.

I will make sure there's no airflow into the gap behind the insulation


One complication of this job is that the rear wall is partially under ground level, i.e. the garden rises 1'6" behind the house.
How is this going to affect moisture and how should i proceed?

[TwoHorsePower]

Greenbeast, for the continually damp bit you could consider extruded polystyrene board? I.e., not the expanded PS board made of white PS balls. This stuff is truly waterproof unlike the PU foam which can hold a lot of water when soaked, to which Noel Squibb & others will attest. Extruded PS performs somewhere between expanded PS and PU/polyiso foam, and in the long term, as polyiso degases over time, will be as good as dry polyiso in the long run.

Possible cheap source for small quantities of extruded PS? In some potentially damp areas of my loft, I'm using knauf space boards 1200mm X 500mmX52mm on the wall. These are intended for loft floors but fine for wall too if correctly fixed and sealed. Cheap enough at £3.50 a board from dreaded B&Q if you only need small amount.

I had a problem years ago with a garage wall damp where the garden was higher than part of the wall. Dug a trench on the outside of the wall, waterproofed the outside brickwork with a few layers of heavy baking foil glued on (& sandwiched) with bituminous paint-on-damp-proof stuff. Then, before refilling the trench with aggregate, some thin cheapo expanded PS set loosely on the outside to prevent the stones from tearing at my good work. Substantially reduced the damp in the garage wall. Stones provide drainage and keep the worst of the water away from the wall. Grass grows over the top of the stones and you would never know what lies underneath. One of my more successful bits of shoestring bodgery.

Perhaps worth considering briefly before someone tells you the correct approach!