Spec for wooden floor

[davey76]

Hi Guys

I need to talk to my builder re. the floor work he has done in our kitchen

How would you spec a ply floor to be ready for tiling? Its on 4x2 joists with a 6' span (joists have extra supports to ground in middle of span)

High traffic area

i.e. thickness of ply, supports, screwing down etc...

Thanks

 

[PrenticeBoyofDerry]

If the floor is not bouncy, 9mm ply should do.

 

[stevebamford]

9mm ?

there are no floorboards underneath - just the joists

 

[Richard C]

Without asking all the same questions & posting the same answers, is this the same builder/problem as your other thread? //www.diynot.com/forums/tiling/reuse-floor-tiles.311291/#2293057

If so why start a new thread! I’ve already explained why your tiles failed after 6 months, given info about over board thickness, the problems associated with tiling over two different floor substrates, your marginal joist size & the maximum span; but you never did specify the pitch!

What happened to the new concrete slab infill? I assume the proposal is to overboard what you already have & not a new floor? If so what is it, 18mm or 22mm ply? 9mm ply overboard just isn't thick enough; the BS, tiling association & all the adhesive manufacturers I know of specify 15mm WBP for overboard; but 12mm is usually sufficient & is the minimum you should use especially in a high load/traffic area such as a kitchen but I thought I already covered that

For a new floor, I would use 25mm WBP in a high load/use area such as a kitchen & that’s assuming the floor joist spec is up to scratch & yours probably isn’t without additional work. But because you have two different floor substrates, what’s being proposed will be no better than last time & without additional prep & precautions, I doubt it will last much longer than the six months the last effort did.

I don’t think your builder has a clue what he is doing as far as tiling in concerned.

 

[PrenticeBoyofDerry]

9mm ?

there are no floorboards underneath - just the joists

sorry misunderstood post I thought floorboards were fitted and substrate required.
In that case something nearer 25mm.

 

[davey76]

no worries prentice and apologies Richard for raising another thread

I've been investigating what he did (at our expense) - 18mm ply, edges not supported by noggins, screwed down every 60cm (more along some edges) - and was wondering what the official spec was before raising it with him

 

[PrenticeBoyofDerry]

Screwed down every 60cm
I would be thinking closer to every 150-200mm along joist.

 

[Richard C]

PBD is right, more like 150-200mm max into the joists. It’s also important how the boards are laid; joints should be supported down the centre line of a joist, cross joist joints must be supported by stout noggins, board joints in the centre of the room or in high traffic areas should be avoided. 18mm can be sufficient in light use/load areas such as bath/shower rooms but your heading for early failure in a high load/use area such as a kitchen &, as before, it all depends on your joist size/pitch/span. Boards should also be acrylic sealed on back (non tile side) & edges to avoid moisture penetration.

As I've said before, your problems are three fold; you have two different floor types & an uncoupling membrane should have been used, the joists & their supports on the suspended part of the floor are marginal & the tiles have been incorrectly laid.

 

[davey76]

Thanks guys