Fixing Hardie backer board (floor)

[Realstokebloke]

Hi, i got in a pickle with an ensuite (recently posted) & am now on the remedials.

Jason the tiler was a fab help thanks - but i can't keep pestering him as a go fwd...

Nearly all told me that my orig ply was too thin on the floor so it all came up again.

I was told to use 6mm Hardi backer to the floor instead.

I have taken up the old ply and am back to the green chipboard. I will now bang in as many screws as possible to the joists to really get it firm (150 centres).

My Q are:

do i just screw the Hardie backer to these & through to the joists, or does it need any prep first ? (hopefully not more ply as i'm trying to keep the height down.)

What screws / centres?

Does it need adhesive?

What if there are any small gaps do i "pack" it?

The when it's down, do i need a two part adhesive or will a flexible do? (tiles are 330 sq. ceramics)

I had a Unibond but have skipped that, so am keen to get it right.

I still have the Mapei flexi coloured grout (it cracked before but due to the thin ply & floor flex i guess) so will that still do?

It hasn't arrived yet and i may get a set of instructions (but i strongly doubt it).

Cheers.

[grumpygrouter]

It is important that your floor is solid before you go any further. If there is any bounce then you will still have problems. If you floor is solid then you lay the hardie down in a staggard pattern using adhesive initally and then screws. The adhesive is only there to fill potential voids underneath the board and not as an adhesive. Use a flexible adhesive both below and above the boards and screw the boards down at about 200mm centres. There are indicating marks on the boards to screw through into the chipboard/joists.

[Bri]

Now that your ply is up, check the floor for deflection (have a really good jump on it) as the hardie will add no strength or stability to the floor, it just provides a suitable surface to tile to. As for laying it, use a flexible adhesive (the same as you will use for your tiles) and screw it at 200mm centres. Leave expansion gaps between the boards of 2/3mm and use a suitable mesh tape to cover the joints before you tile.

[Bri]

Too slow!!!

[Rich]

HardieBacker...


Have a read through this link, should give you a little more info. The guys above are bang on as always.

Swanson, no cement tile backer boards that I know of say that their boards add any strength to the floor, for this reason it is very important to make sure that the floor is deflection free before you fix the boards down not to rely on the backer boards to sort out a deflective floor. If the floor has deflection, the tiles will crack and lift if you use a backer board or not.

[Rich]

YOU no best

No I dont, the manufacturers know best. I was just making sure that the boards would not be used as a way of making the floor rigid as this is not what they are for. Wasnt having a pop.

[grumpygrouter]

Too slow!!!

Yep....

[grumpygrouter]

YOU no best

Rich's information is correct.

[Bri]

So tell me rich


what are they designed for

To give a more suitable surface to tile to/adhesive to bond to.

[Rich]

As Bri says, they are for providing a suitable surface to tile onto. I (and others) have put up loads of posts about this over the years, here a couple. Have a read through



HardieBacker...

Plywood floors...

Tile backer boards are not for making the floor rigid, they will always state that the floor must be deflection free before the boards are put down.

[Realstokebloke]

Cheers guys - double checking - surely i don't need to re-ply it underneath the backer (mentions putting it over 18mm ply in post above)?

Surely the adhesive mentioned fills any gaps etc?

Also assume you mean that you don't need to put further ply down if the floor itself is soild / sound?

Are Hardibacker screws just wall/plasterboard screws (coated)?

And no 2 part adhesive (just in case)?

[grumpygrouter]

Cheers guys - double checking - surely i don't need to re-ply it underneath the backer (mentions putting it over 18mm ply in post above)?

Surely the adhesive mentioned fills any gaps etc?

Also assume you mean that you don't need to put further ply down if the floor itself is soild / sound?

Are Hardibacker screws just wall/plasterboard screws (coated)?

And no 2 part adhesive (just in case)?

The ply would be used to strengthen the floor so if it is solid then you don't need it. You can use a 2 part adhesive if you wish, it wouldn't hurt. Keraquick and Latex Plus is ideal if you can get it. You need non corroding screws for the board, stainless steel is ideal.

[Realstokebloke]

Cheers guys - double checking - surely i don't need to re-ply it underneath the backer (mentions putting it over 18mm ply in post above)?

Surely the adhesive mentioned fills any gaps etc?

Also assume you mean that you don't need to put further ply down if the floor itself is soild / sound?

Are Hardibacker screws just wall/plasterboard screws (coated)?

And no 2 part adhesive (just in case)?

[grumpygrouter]

ok i no when i beaten

No one is trying to beat you mate. We just like to ensure that any information is as accurate as possible. We are all still learning and that is why the forum is here, to help people - any people - that want to learn about tiling.

[Stewart]

ok i no when i beaten

It's not about winning and loosing... The forum is here for us all to learn and keep up to date with the latest info to give our customers the best service possible. I've been in the game for over twenty years and I'm constantly learning.......

[Rich]

Nicely put Bri and Grumps. None of the trusted members come on this forum in there spare time to show how much they know or make anybody out to be stupid, its got nothing to do with being beaten, it is only about giving the correct advice not about clashing swords about who knows the most.

[grumpygrouter]

Walking with kings dosent make you one

Not sure what your comment is supposed to imply! We are only here to help people with their tiling questions and if information is posted that is incorrect then we try to ensure that the right info is passed on. If you have difficulty accepting that then that is a shame. I bet there isn't a tiler on here, even with 30 or 40 years experience who hasn't learned at least 1 thing they didn't know.
You are more than welcome here but please keep sarcastic comments to your self, they aren't necessary!

[jay]

Walking with kings dosent make you one

care to explain this comment
thanks