Ply-boarding over floorboards, pre-tiling

Hi guys,

We're going to tile our kitchen and hallway (as if 1 big room).

We are using 600x600 Porcelain tiles.

The current floor (wood, tongue/groove) are suspended floors and have been butchered over the years and so we need to ply-board the floor prior to tiling.

What is the best ply to use?

The tile centre have advised us that if we use 18mm, we can save about £180 on tile adhesive. Obviously the saving is offset by the price of a thicker ply.

We have 24sq m to do.

Any tips appreciated.

Gallen.

Just to clarify, t&g softwood or t&g chipboard panels? If the former use 12mm wbp ply, if the latter, rip it all up and replace with 18mm wbp ply, adding extra noggins as you go.
Either way you should still use a flexible adhesive over timber.

The other option is cement tilebacker board, which could be used as thin as 6mm over timber floor, not entirely sure if you'd still need flexi adhesive though, but following manufacturers instructions to the letter, or ringing their techie line for advice and you won't go far wrong.

Deluks said:

Just to clarify, t&g softwood or t&g chipboard panels? If the former use 12mm wbp ply, if the latter, rip it all up and replace with 18mm wbp ply, adding extra noggins as you go.
Either way you should still use a flexible adhesive over timber.

The other option is cement tilebacker board, which could be used as thin as 6mm over timber floor, not entirely sure if you'd still need flexi adhesive though, but following manufacturers instructions to the letter, or ringing their techie line for advice and you won't go far wrong.

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Thanks Deluks,

Currently it's T&G 50'/60's softwood floor boards.

Cement tile-backer board? Interesting... How's this used?

Forgot to mention that we're hoping to have a heated floor-space - does this have any effect to what we use?

G.

if the old floorboards are in poor condition, consider pulling them up and laying a new ply floor direct on the joists. This will also stop the new floor sticking up so much.

18mm will do but 25mm is even more rigid. Be sure to have noggins under all short joints and any joints that are not centred on a joist.

taking up the old floor will also make it easy to add underfloor insulation, as well as cleaning out choked airbricks, insulating pipes and removing builders rubbish

I’m not sure if your overboading or replacing? What are the tile centre advising with regards saving money on adhesive? I sincerely hope they are not suggesting you use using a non-flexi addy on a suspended floor

Bath/shower rooms are light load/use but a kitchen/hall should be regarded as a heavy load/use & you should go thicker to avoid any chance of failure. But it’s always dependant on the floor joist size/pitch/span; there must not be any perceivable flex in the floor or the tiles will fail & some cases you may have to beef up the joists as well, particularly on large spans.

You would have done better to have posted in the tiling forum & I would suggest you have a good read through the archive pots in there before going any further; it may save you from making some potentially very expensive mistakes.

Thanks for the move guys

...The tile centre are pricing £250 (approx) for 1 x adhesive based on a 12mm ply over-board, and £76 for another adhesive based on 18mm ply over-board.

The tiles are pure glossy white porcelain (600 x 600) and there is 24 sq meteres to tile, which is hall though to kitchen.

The advice I was given from the tile centre is that the thinner board will need a more flexible adhesive (hence the additional price).

It does seem like a BIG difference though but I am looking for the "right" advice.

If it makes a difference, we are also hoping to install electric underfloor heating here too.

Thanks guys,

G.

Gallen said:

The tile centre are pricing £250 (approx) for 1 x adhesive based on a 12mm ply over-board, and £76 for another adhesive based on 18mm ply over-board. The advice I was given from the tile centre is that the thinner board will need a more flexible adhesive (hence the additional price).

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So it’s an 12/18mm overboard. Needing a less flexible adhesive on the thinner ply doesn’t necessarily follow & I don’t see how they can say that without assessing the floor; unless they have! I really need to know exactly what are the two types of adhesive they are recommending. If the more expensive is a latex based addy & cheaper a flexible then it could be fine but if they are proposing you use a non-flexible adhesive with the thicker board or with just an additive, I wouldn’t touch it with a barge pole.

Gallen said:

The tiles are pure glossy white porcelain (600 x 600) and there is 24 sq meteres to tile, which is hall though to kitchen.

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They are very large tiles & you need to get both the floor & the adhesive type/quality right or it could end in tears. You will loose all the money you will save on addy + an awful lot more if it fails. White tiles on a kitchen floor is not something I would recommend & I definitely wouldn’t advise using white or a light coloured grout. Who’s doing the prep work/fixing?

Gallen said:

If it makes a difference, we are also hoping to install electric underfloor heating here too.

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Electric UFH isn’t particularly cheap to run, it’s also notifyable building work & not something you can easily DIY. But if you’re having it, you would be better off using an insulation backer board under the element (but they ain’t cheap), this will reflect most of the heat upwards resulting in quicker warm up time, flexible screed over the element & then tile over that!

Thanks Richard C,

The tile centre are quoting £250ish for adhesive 1 based on 12mm over-board. Because this would need to be more flexible due to the thinner 12mm board, I am assuminbg this is more expensive due to this.

The adhesive for the thicker 18mm board is coming in cheaper at £75 odd quid. I am guessing that this is due to it being less-flexible due to the added thickness of the board.

I will find out the recommended brands this evening and update accordingly.

The tiles being 600 x 600 and pure white are the look we are after. These will match our worktops which will be either white marble, quartz or Corian. This is a lifestyle choice more than a practicality (and reading that back it sounds really ponsey - but its not meant to. It's just the look we want as our kitchen and house is a very modern style)!
They are a pure white glossy tile and are flat with no texture to them so should not trap dirt and we intend to finish with a grey flexible grout to minimalise discolouration of the grouting as much as possible.

I am getting someone in to do the prep work & tiling (unfortunately) simply as I have no time to do this myself due to it needing to be done before Christmas as we have a baby on the way due in January.

We have electric underfloor heating installed (but not connected up yet) in our bathroom which was bought as a kit (loose wire, not matting). We are after a cost effective solution for the kitchen and hallway, without having to pulll up all of the existing floor boards to fit reflectors. However if I can get some off flea bay during the time available, that may be an option - but its down to time really. I appreciate it may not be the most cost-effective running solution but time os of the essence, so to speak!

I'll find out the adhesive qualities - unless you can reccommend some?

Thanks for your help/advice on this. Appreciated.

G.

I'd brace that floor from below if I were you. Porcelain doesn't like being flexed. It's not a lot of extra effort at this stage.

Gallen said:

... pure white glossy tile and are flat with no texture to them ...

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not that I know about these things, but sounds good for falling over on?

hall/kitchen
there will be heavy traffic going over these areas,
lift the exsisting and relay 22mm wbp primed,screwed and add extra dwangs/noggins.
if using elect ufh, put insulation boards down as well to help your heat up times.

JohnD said:

Gallen said:

... pure white glossy tile and are flat with no texture to them ...

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not that I know about these things, but sounds good for falling over on?

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I agree; the gloss tiles on their own will be slippy enough but get the slightest few drops of water on there & it'll be like a skating rink, could be really unsafe in kitchen. I know it’s a “lifestyle” choice but life doesn’t have much style if your flat on your back with concussion or in traction sling.

Even worse with a sheen of cooking oil.

they're tiling the kitchen, surely no chance of drips or spills?

Gallen said:

The tile centre are quoting £250ish for adhesive 1 based on 12mm over-board. Because this would need to be more flexible due to the thinner 12mm board, I am assuminbg this is more expensive due to this. The adhesive for the thicker 18mm board is coming in cheaper at £75 odd quid. I am guessing that this is due to it being less-flexible due to the added thickness of the board.

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As I said that logic doesn’t necessarily follow so I’d be interested to know exactly what they are proposing.

Gallen said:

I am getting someone in to do the prep work & tiling (unfortunately) simply as I have no time to do this myself due to it needing to be done before Christmas as we have a baby on the way due in January.

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Make very sure you get someone in who knows what they are doing; you have the ingredients for a potential disaster with this one if not. Joe & tictic have some very valid points there & is the direction I am going in.

Also just noticed you’ve got a little one on the way which makes those slippy white tiles even more of a bad choice once it starts walking. I would seriously advise you consider something with a bit of texture on them; I’ve got 3x young grandchildren (only 2 walk at present) & have tiles on a large part of our ground floor area but they are texture porcelain & provide enough grip to prevent accidents even when wet.