tiling over floor grade chipboard

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

Hi Sharpfamily, welcome to the forums.

Your question.... Sadly I must inform you that BAL single part flexible is not suitable for tiling straight onto a chipboard floor. BAL recommend at minimum there Fastflex product which is a 2 part latex based adhesive. They would also strongly recommend that your floor is overboarded with 18mm WBP ply sheeting screwed at a minimum of 300mm centres.

It is imperative that you ensure that your floor has as little deflection as possible as your tiles WILL crack.

If you can not, for some reason, over board your chipboard there are other ways to deal with this, but currently your chosen adhesive is not suitable.

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

Originally Posted by sharpfamily

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

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.

All timber and timber based substrates are are prone to "movement" because of differing moisture content of the environment meaning the timber will expand and contract. All materials expand and contract to some extent but it is when materials "move" at different rates that causes the problem. Your tiles would expand/contract at a different rate to the chipboard, hence your problem.

However, your problem is not unsurmountable as you can, I I have done successfully, tiled straight onto chipboard if you use appropriate materials, AND THE FLOOR IS SOLID! Please note the emphisis there.

There are a number of alternatives. Your BAL Single Part Flexible is not part of it unfortunately. If you really want to tile straght onto your chipboard floor, this is what I would do.

Firstly i would go over the floor and screw the boards down to the joists at no more than 300mm centres with corrosion resistant screws (nails work loose too easily) leave it nailed as well. Then I would prime the chipboard with a product called Ardex P51 primer. Once that is dry I would use an adhesive called Ardex-flex 7001 to fix the tiles.

If you are unable to get hold of the Ardex products you would need to seek out something like BAL fastflex adhesive. This is a 2 part latex based adhesive but it is very expensive and messy to use but it will certainly do the job.

There are other alternatives as well but these include laying a "decoupling" mat of some sort and again will entail additional cost.

good replies there grumps.please take note of what your being advised as spending a bit more now will stop it costing you more in the long run!

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.

Originally Posted by sharpfamily

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.

SERIOUSLY DONT USE THE SPF! There is not enough flexibility in this adhesive for what you want. Take it back and change it for something more suitable. I really think you will regret it if you continue!!

Where did you buy it from and who advised you?

No telling some peeps Russ....

Well, I have tried my best Dave. I know it will crack, maybe not in a week or a month but certainly before the year is up! Such a shame to spend all that money on tiles and not use an appropriate adhesive.

I really hope he takes on board what is said.

unfortunately, they sound like the customers who dont beleive when you tell them what they need to do the job properly and insist on going ahead anyhow. ah well you can lead a horse to water!

PLEASE LISTEN TO US WE ARE NT GIVING THE ADVISE TO MAKE ANY MONEY BUT TO SAVE YOU LOTS!!

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.

Originally Posted by sharpfamily

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.

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.

Hopefully things will be OK for you. Good luck, I hope you are still crack free at christmas.