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Discuss tiling over floor grade chipboard in the UK Tiling Forum area at TilersForums.com.
Chipboard itself is quite an unstable material for tiling onto. Adhesive manufacturers recommend overlaying with plywood for 2 reason, 1. To impart more stiffness to suspended floors to reduce deflaction as much as possible and 2. if chipboard does get wet, it can "blow" i.e it can swell up and push off the tiles.thanks for the advice. there's a bit more info below. I'd be grateful for some more advice as I don't want the tiles to crack! and I've already got the BAL single part flexible adhesive.
The chipboard sheets are glued along their halving joints and nailed down on to battens @ 14" centers (with insulation between) over a damp proofed solid concrete base. ( new construction 1991).
the floor is very solid and there's no sign off any movements or squeaks. There is definitely no movement between the joints in the chipboard.
why is an additional layer of ply wood necessary?
thanks
thanks again for taking the time to give me all the info.
I'm now thinking that my chipboard is the moisture protected flooring grade and it's over a concrete base (with damp proof membrane under). The floor is bone dry and the room is a lounge/dining area & 17years old. So movement due to moisture shouldn't be a problem. The temperature range/thermal movement hopefully shouldn't be a problem as the room is nearly always occupied and is very well insulated.
Gravity loads/movement are not a problem as the floor is solid & I'll put in lots of extra screws as you suggested.
So I'm going to take a chance and use the BAL single part flexible - I've already got the 10 bags of this and as you say the BAL 2 part is very expensive and messy. If it goes wrong....I've only myself to blame!
thanks again.
We have tried to give you advise based on combined dozens of years of experience and tried to explain what problems you are going to have. You have chosen to ignore what has been suggested sadly.thanks to all contributors.
I can't understand a mechanism that will cause the tiles to crack.
- as regards gravity - the floor is solid and vibration proof
- temp - tiling at summer temps, so any differential thermal contraction will only occur over an individual tile, ie given that the grout's tensile strength is weaker that the tile. Thermal expansion and possibility of the tiles buckling not an issue given summer temps.
- moisture. the floor is bone dry, and any small expansion in the chipboard would only have affect across one tile width, and there should be sufficient flexibility in the bal spf to cope with that.
hence I'm going to proceed with the bal spf. I'll be sure to let you know if the tiles crack within the year.
Hello, I am a Product Support Technician for BAL. Unfortunately for you, everything the boys have said is true. If you will not seek the advice of the professionals, or a technical representative of the company who makes the adhesive you are going to install incorrectly, (and if money is the biggest issue) I would ask to be refunded the tiles and adhesive and put a cushionfloor down that looks like tiles. What was the reason for seeking advice if you are not prepared to heed it ? I also think de-bonding of the tiles will occur before 12 months is out......I hope I am wrong !thanks to all contributors.
I can't understand a mechanism that will cause the tiles to crack.
- as regards gravity - the floor is solid and vibration proof
- temp - tiling at summer temps, so any differential thermal contraction will only occur over an individual tile, ie given that the grout's tensile strength is weaker that the tile. Thermal expansion and possibility of the tiles buckling not an issue given summer temps.
- moisture. the floor is bone dry, and any small expansion in the chipboard would only have affect across one tile width, and there should be sufficient flexibility in the bal spf to cope with that.
hence I'm going to proceed with the bal spf. I'll be sure to let you know if the tiles crack within the year.
What you appear to be not understanding is that the atmosphere around your floor will vary constantly with temprature and moisture content of the air. Even though your floor is "bone dry" the atmosphere containes moisture and you have heard of this referred to as humidity. Different weather conditions WILL affect your floor even though it is dry. This is the reason you have ventilation under a suspended floor and also the reason why you have insulation boards between your joists.I can see why is chipboard not suitable for tiling in some circumstances.
However my chipboard floor is solid, no deflections....therefore I see no need for adding ply for extra stiffness.
the chipboard is bone dry, been down for 17 years and is not subject to any wetting or moisture.
please explain in more detail why you foresee cracking or debonding before Christmas.
Thanks for your comment Graham. I am here to help if I can.Grumpy,
Thank you for sharing your practical knowledge so patiently.
That's what will make this forum work.
Others perhaps should take note the good example you set.
best,
graham
i'm tiling (500*500 tiles) over floor grade chipboard using bal single part flexible. do i need to apply a primer, if so why, and which primer?
thanks
graham , if the floor is solid overboard with 9mm ply screwed every 150 centres, it wont cost much and is a fairly easy job, time and money well spent for peace of mind and will save you a packet on the long run..I can see why is chipboard not suitable for tiling in some circumstances.
However my chipboard floor is solid, no deflections....therefore I see no need for adding ply for extra stiffness.
the chipboard is bone dry, been down for 17 years and is not subject to any wetting or moisture.
please explain in more detail why you foresee cracking or debonding before Christmas.
thanks to all contributors.
I can't understand a mechanism that will cause the tiles to crack.
- as regards gravity - the floor is solid and vibration proof
- temp - tiling at summer temps, so any differential thermal contraction will only occur over an individual tile, ie given that the grout's tensile strength is weaker that the tile. Thermal expansion and possibility of the tiles buckling not an issue given summer temps.
- moisture. the floor is bone dry, and any small expansion in the chipboard would only have affect across one tile width, and there should be sufficient flexibility in the bal spf to cope with that.
hence I'm going to proceed with the bal spf. I'll be sure to let you know if the tiles crack within the year.
Ardex-flex 7001 is a single part addy designed for the very same thing and also works a treat. Cheaper too.I have recently tiled onto chipboard on 2 floors (against my advice) with the only adhesive I would have trusted - Bal Fastflex. Worked a treat, not very messy to use either. I also used the GT1 (?) Admix to the grout to prevent cracking in the grout. No problems. Definitely wouldn't have used a single part.
Good luck with it
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