Insulating external bathroom walls - Options?

[stoobloo]

I'm going to be fully tiling the walls in our bathroom and wondered what would be tried and trusted method to giving the external walls extra insulation.

Our house is cavity walled with insulation in the cavity, but based on our old house (same construction) the bathroom wall was always cold, so any way to reduce this extreme would be great.

I'm looking for the best insulation properties as well as something I can tile straight on to ideally. Presumably whatever 'boards' I use will be dot and dabbed and then mechanically fixed also?

 

[^woody^]

The easiest would be 50mm insulated plasterboard. 25mm if space is tight.

By virtue of it being a bathroom - which will be (or should be) vented via an extract fan, you won't need to over insulate it, just do enough to take the chill away.

Does the ceiling insulation need toping up?

You should skim the boards, don't tile on to bare boards - you'll regret it when it comes to retiling.

 

[Ivor Windybottom]

Plasterboard is frowned upon by many for use in bathrooms at all as, despite best possible practice in tiling and sealing, it can end up turning to wet sludge and collapsing in a heap. It's just paper and gypsum, water resistant grade is not waterproof and neither is grout - it may be OK for a ceilling, but not for a shower.

Tileboard (Tile Backer Board) is best, it's very rigid and is made of plastic foam so is waterproof and has insulating properties. It may be that a U-value isn't stated but it undoubtedly insulates, more if thicker.

Lots available from all merchants, tile shops, DIY sheds etc. Here's one example for reference...

Thermal Construction Board - Various Thicknesses

Shop the Tilemaster Adhesives Thermal Construction Board. Resistance to water makes them ideal for bathrooms. Now at Victorian Plumbing.co.uk.

www.victorianplumbing.co.uk

 

[JohnD]

If space is tight, you can hack off the old plaster. This will give you extra space, fir example if the bath is tight to the wall and can't be inched out.

I thought I saw Hardie Backerboard with a bonded foam layer?

 

[^woody^]

Plasterboard is frowned upon by many for use in bathrooms at all as, despite best possible practice in tiling and sealing, it can end up turning to wet sludge and collapsing in a heap

Really? Every bit of plasterboard in a bathroom is at risk of getting soaked?

Are you are rep for Hardiebacker, or just a victim of brochure marketing hype?

 

[Ivor Windybottom]

It's becoming standard practice to avoid plasterboard in bathrooms. Well, probably not for newbuilds but definitely for anyone who cares about its long term prospects.

If you want to throw a bathroom together for as little as possible and don't care about the long term then plasterboard is perfect!

You could get away with it anywhere away from a shower. But just tileboard the lot, it's foam-cored so will definitely insulate a lot better than plasterboard.

There are loads of brands, there's no sneaky conspiracy, it's just better.

 

[Ivor Windybottom]

This bloke's sponsored by a manufacturer, but I'd say his advice is relevant...

 

[Ivor Windybottom]

I've used decent Mapei "water resistant" cement-based (powder mixed) grout in our shower, it's light grey.

It goes dark grey after a shower, for several hours afterwards until it dries again. It's definitely not waterproof, if there was plasterboard below it would get wet every time.

 

[freddiemercurystwin]

Actually in July 2023 NHBC updated their standards to make tanking to walls surrounding baths/shower enclosures etc mandatory for certain types of plasterboard (ie standard) with either liquid/membrane or board.

https://r.search.yahoo.com/_ylt=AwrkPXyhPVZl.BQc4REU8yA5;_ylu=Y29sbwMEcG9zAzUEdnRpZAMEc2VjA3Ny/RV=2/RE=1700179490/RO=10/RU=https%3a%2f%2fwww.nhbc.co.uk%2fbinaries%2fcontent%2fassets%2fnhbc%2ftech-zone%2fnhbc-standards%2ftech-guidance%2f9.2%2f9.2-06-substratesfortiling.pdf/RK=2/RS=54Lvahpn5bCLuZmGhe3T.KMHmUA-

 

[mikeey84]

I just dot and dabbed, with mechanical fixings, 40mm thick XPS tile board round pretty much all of my bathroom. Marmox or similar

It's made it very cosy!

100% water proof, tile straight onto it and dead easy to put up, took me less than a day, including some awkward cuts.