Putting down hardiebacker board

[Hulloo]

Hey people hope u can advise me.....I am currently installing a new shower room in my house. Im upto the stage of tiling the floor. The floor is made up of wooden floorboards on wooden joists.

The floor was slightly unlevel so i decided to use everbuild self leveling compound after priming with SBR bonding and securing down any loose floorboards. This has given a great result.

The next stage is to lay down the 12mm cement based hardie backer boards.

To give the boards that extra security before screwing down using the galvanised screws, I have decided to lay the boards down on a very thin bed of dri wall adhesive (Had a spare bag lying around) then screw down when set.

My question is if i follow the above procedure would i first need to prime the self levelled floor with PVA for the dri wall to give the hardie backer a secure fix? If so what ratio mix of PVA to water and for how long should I leave it before laying the boards......

Many thanx, hope u can help.....

 

[Mike]

the correct order should have been strenghthen and screw down floor boards, if then solid enough (no deflection) prime and lay down hardi boards with 1 part flexi adhesive and screws then slc if required. also we don't use p.v.a in tiling , the primer you mentioned is ok though

 

[Hulloo]

Is it no good then to use the spare dri wall bag i have? As I have already laid the slc what would u suggest i do next? Many thanks for the quick reply

 

[The Legend; Phil Hobson RIP]

I would forget the PVA and the drywall adhesive, use SBR to prime, then a flexible tile adhesive to glue and screw the boards

 

[doug boardley]

Mikes method is the correct procedure.

 

[Hulloo]

I would forget the PVA and the drywall adhesive, use SBR to prime, then a flexible tile adhesive to glue and screw the boards

Ok thanks i will do. Just a couple of things.....How should I dilute the SBR and how long shall i leave it before laying the boards....Many thanks, u have been great help

 

[Hulloo]

Oh and 1 final thing sorry to be a pain, when laying the boards with the floor adhesive should i use a notched trowel or lay them on a full bed....Many thanx

 

[Mike]

what about the slc already on the floor boards doug/phil?

 

[Mike]

a notched trowel will be fine and when the board is screwed down it should be a solid bed then

 

[Hulloo]

a notched trowel will be fine and when the board is screwed down it should be a solid bed then

What ratio should i mix the SBR to prime the slc with and alo how long should I leave the SBR before laying the boards down?

 

[The Legend; Phil Hobson RIP]

As Mike says, the correct method is as he states, if the slc is the type that can be used over timber then you don't have a problem. The boards can be glued and screwed using a notched trowel, but if your slc is not suitable for timber you may have to lift it and go the route Mike suggests. Not many slc products are usable on wooden floors

PS. most SBR dilute 3:1 with clean water, but check with manufacturers instructions

 

[Mike]

it will say the ratio on the can, probably 3 or 4 water to 1 sbr. leave it till its soaked into the slc, (shouldn't take long though) i'd be cautious of the slc though as you'll be screwing through it, it may crack between the floor boards and backer boards

 

[Hulloo]

As Mike says, the correct method is as he states, if the slc is the type that can be used over timber then you don't have a problem. The boards can be glued and screwed using a notched trowel, but if your slc is not suitable for timber you may have to lift it and go the route Mike suggests. Not many slc products are usable on wooden floors[/

The SLC was suitable for wooden floors

 

[Mike]

i would suggest trying a few screws through the slc and into the floorboards to make sure the slc don't crack as you won't be able to see once you overboard

 

[Hulloo]

i would suggest trying a few screws through the slc and into the floorboards to make sure the slc don't crack as you won't be able to see once you overboard

the slc already has a few thin crack lines......is this not a good thing? as per man instructions the floorboards were primed with SBR....Would the flexi tile adhesive between the backer boards and SLC resolve this?