Advice on replacing a floor please.

[kaharrison9]

Evening all.
Hoping somebody can give us advice on the correct way when replacing a floor.
I have chance of taking on what for me will be a large job.A customer is knocking through and tiling from his kitchen to dining room.At the moment in the kitchen the tiles have been stuck directly onto chipboard which was nailed down and there are many lines of cracks in the tiles where the edges of the chipboard is.
The customer has asked if i'll replace the sub floor and eliminate any future cracks when i retile.
If needed how far apart should noggins be and is there a technique when fitting them to the joist?
Will i need to use 25mm wbp ply,can you get it tongue and groove and is there any specific screws i need also is there a maximum distance between screws?
Finally would there be no need for say a 6mm hardibacker board to lay on top?
Thanks for any answers or other advice.
Kev

[mikethetile]

hiya kev

dont understand the noggin bit, you lay the boards across the joists so that the end of the boards are on a joist. the edges are supported buy the tongue and groove. use chipboard flooring and fix with spax screws @ 150 mm centres.

stagger the ends of the boards so you have a brickwork pattern

you can overboard or use the uncoupling method, see relevent section on this forum for a full explanation

if you over board screw down well as the idea is to eliminate as much movement as possible and to reduce bounce, again i screw down at 150mm centres

[Oli]

As you are removing the existing sub floor, get rid of all the chipboard, replace with 25mm WBP, add extra noggings inbetween the joists where the board ends will land, and anywhere else where there is still deflection / movement .

The boards should be staggered and screwed down every 150mm I use turbogold screws from screwfix, although some say 300mm is adaqute so its up to you there. Dependant upon which adhesive you use some will suggest to only prime the underside and edges of the ply, some will suggest priming it all. You wont need to overboard the ply with anything, you can tile directly ontop of it. You shouldnt tile onto chipboard, its make up doesnt make it good for tiling onto, as your client will probably already be all too aware of. The adhesive manufacturer will be able to indicate a suitable primer, NOT PVA!

[Frosty]

Yep, I agree with Oli on that one... 25mm wbp if full replacement.
Do it right, do it once!!!!
Extra noggins where required at joints, I always screw down at least 150mm centres just to be sure.

Remember there are no shortcuts worth taking on a full replacement!!!!

[kaharrison9]

Cheers for your quick responses-very much appreciated.
With the noggin is there a specific thickness like 3 inch square and would i be right in cutting the width of the 2 joists and simply screwing through the side of the joist into the end of the noggin?
Also out of curiosity why do you prime the underside of the ply?
Thanks again
Kev

[graham31]

Cheers for your quick responses-very much appreciated.
With the noggin is there a specific thickness like 3 inch square and would i be right in cutting the width of the 2 joists and simply screwing through the side of the joist into the end of the noggin?
Also out of curiosity why do you prime the underside of the ply?
Thanks again
Kev

To stop it absorbing moisture from sides and underneath,which may result in delamination of the tiles