Is 6mm backerboard really enough?

SJRSJR · 23 May 2014

I know this subject has come up from time to time but it seems there are split opinions - is tile backerboard an adequate alternative to ply?

I'd like to get the hallway tiled which currently is floorboarded. The rooms off it are sanded floorboards, so to add at least 12mm ply on top will create a height issue Because of its shape it would be quite a big job to replace the floorboards altogether with 25mm ply so I would like to avoid that.

I've read up and seen the Hardie backerboard video which recommends 6mm thickness and it all looks very straightforward - too straightforward in fact. Would 6mm really provide an adequate non-flexing base even if every board was solid as could be and the instructions were followed to a t? Thanks

tpt · 23 May 2014

Yes - in general

we sell a huge amount of no more ply a month, to trade and retail and only see failures if its been badly fitted or assessed - no different to ply in that sense. We also sell hardie an its a similar story.

Regardless of using a cement based board like no more ply or a more modern lightweight version like hardie, the key is fitting it properly.

Check the floorboards you have, make sure they aren't loose or rotten, screw them down (watch for pipes!).

Personally i prefer no more ply because of the method of fixing - you use a solvented adhesive like no more nails and 8 screws per board instead of, in the case of hardie flexi tile adhesive.

once thats down you'll notice an immediate difference, the floor feels solid and less noisy. It works really well, we seldom see a failure, and when we do its usually because they didnt screw and glue, or the floor was knackered in the first place.

AdamCH · 23 May 2014

It's not intended to stop the floor flexing vertically so make sure the floorboards don't deflect/bounce before it's fitted.

SJRSJR · 23 May 2014

Thanks, that's re-assuring. The floorboards are in good condition and the distance to the middle point of each joist is 17". They're currently nailed down but I'll add some screws too. There are 5mm gaps between some boards - could that be a problem?

tictic · 23 May 2014

SJRSJR said:
Thanks, that's re-assuring. The floorboards are in good condition and the distance to the middle point of each joist is 17". They're currently nailed down but I'll add some screws too. There are 5mm gaps between some boards - could that be a problem?

Shouldn't be a problem....

Just follow mf instructions....

Ie...stagger the boards ect...

tpt · 23 May 2014

in case it helps... http://www.nomoreply.net/installation/overboarding-timber-floors/

the joist centres sound fine. no issue with the gaps, that just sounds like normal floorboard shrinkage.

SJRSJR · 24 May 2014

Thanks all, much appreciated.

SJRSJR · 24 May 2014

Sorry for re-opening this, but if I wanted underfloor heating is it correct that something like Wedi or Marmox should be used as they have better insulating properties? Is that in addition to, or instead of Hardiboard or Nomoreply? Thanks

AdamCH · 25 May 2014

Yes, you need an insulation board. Lay min 10mm Marmox or equivalent straight onto the floorboards - use tile adhesive and mechanical fixings. No need for hardie or no more ply.

Instructions at http://www.marmox.co.uk/products/marmox-waterproof-insulation-board

Fordy81 · 25 May 2014

Sorry to hijack the thread, but is the adhesive under hardiebacker really necessary? My concern is that if ever I need to pull it up the floorboards underneath will be wrecked.

tpt · 25 May 2014

yep. for two reasons really - 1)they wont back you up without it, and 2) it stops movement which is the main reason. In all seriousness, we do see failures from people who dont.

SJRSJR · 9 Jun 2014

One more question on this please. My hallway is 1260mm x 4500mm and the board size is just short at 1200 x 800. Could I use a full board with a 60mm strip along the edge which won't see any weight on it, or should I make them even sized? If I did the latter would there be a weak spot where the boards join I.e. In the centre of the hallway where there is most traffic? I know the joins needed to be staggered. Thanks.

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Is 6mm backerboard really enough?

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