Bit of help for a newbie please!!

[Peter W]

Hi,

Any help on this would be v much appreciated.

I'm tiling a bathroom floor next week. It is a 5 year old house so has 18 mm green chipboard down instead of floorboards. This green chip is laid on 9 inch joists and it is very solid indeed.

On top of this i am putting 12 mm hardie (spelling?) backer board so i'd imagine this will be a very rigid substrate.



1) The chip is nailed down at the moment. But do i HAVE to screw this down before i lay the backers as i'd have to take it up first (messy with tongue and grooves) to check for pipes / wires. And why does it need to be screwed, to stop expansion contraction of the wood or to make it more solid? As it already is.

2) Also, do i have to leave any gaps between the backer board or do i butt is up against the neighbouring piece.

3) Do i prime the backer board? I use Bal primer.

4) At what intervals should i screw the backer board into the chip.


Many thanks in advance for any help


Pete

[GazTech]

Hi Pete welcome to the forums,
systematically punch and nails home that are in the chipboard, then pilot and screw your hardibacker down at 300mm centres ( ceramic coated hardi screws are available) as long as they are no longer than thickness of backerboard and chip you are ok. You can use single part or rapid set flexible adhesive, and polymer modified grout. I would leave a 3mm join between backers and fix them staggered( no need to prime them, but wash them with damp sponge to remove dust before fixing tiles), hope this answers your questions.....Gaz

[Varley]

Yip, exactly as Gaz says mate, the only difference is I only leave a 2mm gap between boards, makes no real difference.

[grumpygrouter]

Personally I would screw down the chipboard to the joists too. Shouldn't be a problem with pipes and cables really.

[Peter W]

Thanks for the advice guys and thank you also for the welcome!

The nails are already punched home so that they are level with the top of the chip, so is that sufficient?

Just want to be properly sure i'm doing the right thing as i've already had some floor tiles crack on me (see my previous thread...)

What is the idea of the staggering out of interest?

Many thanks,


Pete

[Peter W]

Oh yeah, also, i've bought they BAL Rapidset flexible floor adhesive and BAL Superflex for the grout. Will this be ok?

[GazTech]

Your choice of materials is spot on Peter, and the reason for staggering joints is the fact it has more strength, bricks are layed the way they are for rigidity, the same method applies to plywood when layed...........Gaz

[Fekin]

I'd use that, as long as the floor was solid, other wise I'd use Bal Admix AD1 with the adhesive for more flexi.

Superflex.. that's wide joint init, I forget now,

[Dave]

If you are going to use flexible additive with your adhesive then don't add it too an adhesive that is already flexible this will upset the chemical balance and could cause failures.......only add to normal none flexible adhesives.....

[Peter W]

Excellent, all sounds very good advice and i will take note of all.

Cheers again.