Tiling porcelain tiles over plywood with Hardiebacker and Fastflex

[jlondon]

First solo job this week...:smilewinkgrin: It's a small kitchen extension (6m[SUP]2[/SUP]) that the customer wants tiling in 450x450 unglazed porcelain tiles (8mm thick). The subfloor is plywood over wooden joists (1 3/4 x 5 3/4). The current floor over that is chipboard then some green fibre underlay and some cheap and nasty pressed fibre tiles on top.

The subfloor feels a little bit bouncy and creaky, so my plan is 6mm Hardiebacker screwed and glued with BAL Single Part Flexible addy to give a bit more stability to the floor. On top of that then will be BAL Fastflex and then the tiles with a 7mm spacing. Both addy layers will use a 10mm round-notch spreader. The total floor height currently is about 25mm, I should end up about the same (two addy layers ending up at about 6mm each, 6mm of Hardiebacker and 8mm of tile). Does this make sense? Or should I use Fastflex for both layers for a few quid more?

 

[White Room]

Id be making sure you have no flex in the floor before proceeding...7mm joints with glazed porcelain???

 

[jlondon]

Sorry, unglazed, they're a sort of farmhousey rough-stone style. Edited.

I think some of the flex is in the chipboard/fibre tile layers, but what happens if I get it up and the floor is still a bit flexible?

 

[Dave]

The subfloor feels a little bit bouncy and creaky,

err on the side of caution and check suitability before proceeding...or something is going to bit ya bum big style.

Preparation is the key to success .

 

[peterwhayward]

Would definitely be looking to beef the floor up a bit. its only chipboard ( cheap) so take some up and at least make sure there are plenty of noggins in between the joists. Make sure it is screwed down very tightly and not nailed. (don't know why builders do that its no good even if you are not tiling the floor. Cheap I suppose).

 

[jlondon]

Well, when all you have is your DeWalt power nailer, then everything looks like cheap nails?

The subfloor is plywood, the chipboard is laid on top with minimal screwing (4 or 5 per sheet from the looks of the bit I could reach). Hopefully I can get the plywood up for a look-see, but there's a wood floor in half the extension that's staying, I bet some sheets go under it. :mad2: