Hi guys i plan to lay some ceramic floor tiles in our extension and have a query regards floor preperation.The existing floor is Caber particle board 18mm layed/nailed to 2x4 floor joist. The Caber seems solid all round with no bounce and so wonder if 6mm ply would be a suitable base for the tiles if it was screwed say every 100mm?. Many thanks in advance,Colbs.
Floor prep
- Thread starter Colbs
- Start date
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Always suggest 12mm ply minimum, cost difference is negligible but the results are not.
Hi the reason i was hoping to use the 6mm ply is ive got some already from a past job.Would it be ok to double layer the 6mm too
make the 12mm thickness as suggested?.If it can be double layered should i screw each layer down individually or can i screw both down in one go and would i still need screws every 100mm or can i spread them out further?.Thanks again,Colbs
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make the 12mm thickness as suggested?.If it can be double layered should i screw each layer down individually or can i screw both down in one go and would i still need screws every 100mm or can i spread them out further?.Thanks again,Colbs
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2 x 6mm sheets of overlaid ply will not give the same rigidity as a fully bonded sheet of 12mm ply & if it’s not WBP, you shouldn’t use it anyway. Seal the backside & edges with acrylic primer before laying & screw fix at 150mm max through into the joists (check for pipes & cables) not just into the top of the original floor which must be securely fixed before you start. You could go for 6mm tile backer boards but I wouldn’t use them over chip, it’s crap & about the worst possible tile base you can get. I won’t overboard it & would advise you replace with WBP ply; actual thickness you need will depend on your floor structure. 4” x 2” joists are very slender unless the floor is supported by closely spaced brick piers or dwarf walls, can you advise? What’s the joist pitch & span? Is this a light load/use area - bath/shower room; or a heavy load/use area such as a kitchen/hall?
Hi the room to be Tiled is a rear extension of about 35sq mts which will see moderate use.The 2x4 joists are spaced at 400 centres from what i can tell after lifting certain areas of Caberfloor to re-lay.The room is fairly wide so most of the joists have been lapped alongside eachother to create the span and rest on regular joist supporting walls (as i call them).The Caber seems fairly solid now ive lifted and relaid the areas that had movement in them.
I take on board the point about 2x6mm not having the rigidity of a 12mm sheet and guess a re-think is in order?. Colbs ps the room is 16ft wide running with the joists.
I take on board the point about 2x6mm not having the rigidity of a 12mm sheet and guess a re-think is in order?. Colbs ps the room is 16ft wide running with the joists.
So what's the span (distance between) the "regular joist supporting walls" as you call them?
If youve had to do that, IMO your wasting your time.
Hi there i went out yesterday and parted with £180 for 13 sheets of best Brazilian WBP AT 12MM thickness and im going to collect some Bal primer for back and sides of sheets today.I went round the room on hands and knees and discovered lots of the Caber wasnt even screwed/nailed down hence the movement,due to dust etc on the floor i totally missed that minor detail 
. The joist supporting walls look to be spaced every four feet +/-.Ive gone round and screwed the Caber down which in all honesty has made a massive difference over the span of the floor.Richard C can you suggest a good brand of flexible adhesive,the guy in my local tile store has suggested some stuff at £62 per bag but i didnt get the name of it. Im going to screw the ply into joists as suggested at 150mm spacings max and plan to buy Spax screws to go through Ply into caber does that sound a good plan?.Cheers
. The joist supporting walls look to be spaced every four feet +/-.Ive gone round and screwed the Caber down which in all honesty has made a massive difference over the span of the floor.Richard C can you suggest a good brand of flexible adhesive,the guy in my local tile store has suggested some stuff at £62 per bag but i didnt get the name of it. Im going to screw the ply into joists as suggested at 150mm spacings max and plan to buy Spax screws to go through Ply into caber does that sound a good plan?.CheersHi I am not a tiler but 4x2 joists are very small especially for a new build extension. I think you need to buy the best flex adhesive money can buy. good luck
Hi I am not a tiler but 4x2 joists are very small especially for a new build extension. I think you need to buy the best flex adhesive money can buy. good luck
As I said previously, chip is possible the worst tile base imaginable, personally I won’t overboard it & especially in a heavy load/use area such as kitchen/hall etc. I would replace it. You should be OK with 22mm WBP but for extra security you could go to 25mm.Hi there i went out yesterday and parted with £180 for 13 sheets of best Brazilian WBP AT 12MM thickness and im going to collect some Bal primer for back and sides of sheets today.I went round the room on hands and knees and discovered lots of the Caber wasnt even screwed/nailed down hence the movement,due to dust etc on the floor i totally missed that minor detail
Maximum span of 4” x 2” joists @ 400mm centres is around 1.9m. With supporting piers/walls at 4ft your well inside that so the floor structure is OK for tiling providing you use suitable flooring, as above.
That’s very expensive, sounds like it may be an S2 elastomeric adhesive, probably recommended because of the chipboard base. What type & size of tiles are you laying?
Check for pipes & cables but I would have replaced the chip. It’s a large area & even without the tiles, the cost of quality materials is going to be a fair bit. You should ponder over the cost of possible tile failure if you get it wrong, it will make both your eyes & wallet water!
It’s a largish area, what is the shape & principle dimensions of the tiled area? You should allow for expansion & may need an expansion joint, depending on the shape of the room &/or longest tile run.
Hi Richard after your advice im returning the 12mm ply and have ordered 25mm Wbp with a view to ripping up the Caber.Can you please advise on expansion gaps between sheets and also perimeter at skirtings.I will treat back and sides as advised and screw through into joists at 150mm spacings and join ply across joists.Will i still need the highest grade adhesives or can i offset the high price of 25mm ply against a slightly lesser adhesive?.Thanks for advice upto now.Colbs. ps the tiles are two sizes 45x45 and 30x30 which i plan to lay staggered pattern.
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