Hardiebacker Board - Which Adhesive

[Willmott85]

Evening all,

Ive just ordered hardiebacker board to install in bathroom.
Wall - Will be installed directly onto existing masonry
Floor - Will be installed on to 18mm WBP, with a further sub floor of 18mm WBP beneath.

I have read conflicting information with regards to which adhesive is best used. James Hardie recommend on their site non-flexible adhesive for the floor, and a high strength cartridge adhesive + mechanical fastener for the walls.

However, reading various forums online people have suggested normal plasterboard adhesive for walls or flexible tile adhesive, and flexible tile adhesive for the floor.

In my mind non-flexible tile adhesive is best for the floor, as it ensure the boards can not move (despite the fact I have a very rigid floor underneath the hardiebacker). For the wall I would have thought the same theory applies.

Flexible or non-flexible tile adhesive for the floor?
Cartridge adhesive or flexible/non-flexible tile adhesive for the walls (I will use mechanical fastener with chosen adhesive too)

Many thanks in advance for any help you can give.

 

[AdamCH]

They specify non flexible for floors but most pros seem to use single part flexible (SPF). Doubt it makes any difference. Remember to mechanically fix as well with screws.

For walls onto masonry I'd use Marmox not Hardie - it's easier to work with. Hardie say it can't be dot & dabbed but Marmox support D&D with mechanical fixing through the dabs. With Hardie you need a full bed which uses more adhesive. Use file adhesive nor plasterboard adhesive & prime the brickwork first.

Marmox & Hardie publish fixing instructions on their web sites and have good technical phone support.

 

[Willmott85]

Hi Adam,

Thanks for the reply.

I have already got the hardiebacker, so not able to use Marmox for this job. Out of interest why is it easier to work with? Maybe for next time.

Are you suggesting to mechanically fix the floor boarding too?

Ref the wall, they have come back to me and said as long as mechanically fixed, D&D is actually ok. They just don't advertise as such as people may only D&D with no mechanical fix.

Are you able to recommend a tile adhesive for the wall, and also a primer?

 

[AdamCH]

Mainly Hardi is horrible to cut - make sure you don't breathe the dust.

For floors you use a thin bed of tile adhesive (6mm notch) and screw down (the board's marked to help). Use a zinc screw. No need to use the Hardie screw - most use something like Screwfix Turbos.

The adhesive is supposed to be there not to stick the board down but to fill any voids but in reality it also sticks it down of course. Stand on the boards to make sure they're well seated and screw it down while it's still wet.

I used Weber Rapid SPF (it's a flexible) which worked a treat.

If it's cold then the rapid should be fine as long as you don't mix too much at a go. If it's a bit quick then Weber.set plus is the standard set.

The primer I used was and Weber AD250. You can use this suitably diluted on the back of the ply before it's laid, on the walls and on the Hardie board before you tile (it doesn't have to be primed but it's quite absorbent & priming helps unless the adhesive is a very thick bed).

Prices - http://www.tiletown.co.uk/default.aspx?pageid=960

 

[Willmott85]

Hi all,

I am finally getting round to fixing the hardiebacker board to the masonry wall now its all been tidied up. I have the adhesive and the mechanical fixings, and some Cementone SBR for priming.

Couple of questions about the application of the SBR.

- Is it applied as-is direct to the wall? Or does it need to be mixed with anything (Back of packaging has applications for bonding slurry, floor toppings/screeds & external waterproof renders listed which all require sand/cement etc)

- Is it applied and allowed to dry, before then installing the hardiebacker with the adhesive/screws?

- Worth priming backside of Hardiebacker before application or not?

Many thanks in advance for the help!

 

[Willmott85]

Any advice guys on the SBR primer questions above?