Fixing marmox to brick/block walls for tiling

[Pete Verdon]

In tiling my bathroom, I've decided to bite the bullet and board everything with 6mm Marmox before tiling onto it. This might be overkill, but much of it needed waterproofing anyway (shower), extra insulation on the external walls won't hurt, and in places (behind the bath and existing shower cubicle) the walls are a bit bashed about. It just seems easier to board over everything and start with a flat, clean, waterproof surface everywhere.

However, I'm unsure how to fix the boards to the wall. I've seen recommendations to plug and screw, but that sounds like a lot of work for a whole room. Would it be acceptable to simply stick the boards to the wall with tile adhesive or similar (and if so, what kind)? Three of the walls are external or party (so presumably brick or block); the remaining I think is plasterboard (hard to tell right now as it's behind the shower). I mentioned "bashed about", but it's nowhere near bad enough that I'd be worried about chunks coming off taking the board with it. I haven't chosen the tiles yet, but I'm not planning on anything especially extravagant and heavy.

Cheers,

Pete

[meow2222]

I've been reading up all about this, and decided in the end not to go the board route. Hardibacker is more popular. I gather you can adhere it or screw, or indeed both. The mfr specifies what type of tile adhesive, IIRC its thinset flexible waterproof tile adhesive.

NT

[Pete Verdon]

I opted for the marmox largely because of the insulation value. Obviously 6mm isn't going to be fantastic, but might help with the minor condensation I've been getting on the outside walls and will reduce the amount of underfloor heat wasted into the kitchen ceiling.

Pete

[Tim S]

Pete Verdon coughed up some electrons that declared:

I would screw it to the PB wall - ie just put non rusting screws into the wood studwork, assuming it is a wood stud wall(!). And seal/tape the marmox board joints so it's 100% waterproof.

I'm going to glue mine down to concrete with Mapei Keraquick - but the weight is working with the glue.

In your case, the weight of tiles is working against it. How strong is your substrate? Is it possible the plaster might shear off down the line? OTOH, marmox weighs bugger all and people tile walls.

Hmmm. Not clear cut.

As for which glue, you could do waht I did and phone Mapei (or another's) tech support. They gave me a recommendation and a limitation, so I could make an informed choice.

Cheers

Tim

[meow2222]

I worked out the heat savings for half inch board, and the costs for board plus adhesive, and the ROI was pitifully small. Cavity wall insulation gave far more payback at about a sixth the cost.

Filling holes in the wall makes sense, and the different levels on the wall I intend to deal with by using a different spreader for each area/ patch to bring them to the same level before applying tiles. It all costs 2-300 less, and much less heat loss.

NT