make up height difference-best way?

[bluesky]

hi all .been asked to lay original style sandstone in new extension 7.5m x 3.9m .new chipboard base has been laid and nailed down .need to make up a height difference of 27mm (actual is 45mm before tiles 12mm /adhesive 6mm).thought about 15mm ply then 12mm hardibacker ?any other ideas much appreciated .

[whitebeam]

chipboard nailedget some decent screws into that before you do anything else

[peckers]

as white beam says screw the chipboard down first then as you have said will be ok.
whats under the chipboard its not a floating floor is it
is it in a area thats going to get wet?

[david campbell]

after screwing the chipboard why not lay 25mm ply?

[bluesky]

customer stated that it is block and beam then battens with insulation in between and standard chipboard is then nailed to battens - feels very solid .if i lay 25mm ply is it more advisable to use ditra decoupling membrane orbetter to 15mm ply and then hardibacker ?they didn`t want a screed base as it needed to be tiled a short time after even though now it is 4 weeks since the screed would have been laid and will now cost a considerable amount more.thanks for your help

[peckers]

what is the size of the area to be tiled?
is it in one room or more?
is it likely to get wet?
is there under floor heating or electric under tile heating to go down?

[Dave]

I would go 25mm ply and a thicker bed of adhesive..

[bluesky]

30 m2 ,one room lounge area - no wet area , orig style sandstone to be laid with no ufh.

[Ajax123]

Have you checksed it for deflection. Block and beam can be a bit bouncy. also how are the battens secured? Is there a DPM grade polythene over the block and beam before the battens and insulation are placed?

[peckers]

30 m2 ,one room lounge area - no wet area , orig style sandstone to be laid with no ufh.

firstly as someone else has said re screw chipboard down, then apply 25mm ply staggering the joints and going the opposite way to the joints on the chipboard screw down every 200-300mm I wouldnt use ditra as there is no heating on the floor and its not going to get wet, no need for extra expense and prime ply and tile with spf as long as floor is solid as you say. leave expansion around edges of room that can be hidden by the skirting

[bluesky]

floor very solid - no deflection and will check re dpm and how battens are fixed.thanks ajax.

[Dave]

firstly as someone else has said re screw chipboard down, then apply 25mm ply staggering the joints and going the opposite way to the joints on the chipboard screw down every 200-300mm I wouldnt use ditra as there is no heating on the floor and its not going to get wet, no need for extra expense and prime ply and tile with spf as long as floor is solid as you say. leave expansion around edges of room that can be hidden by the skirting

Just to add...UFH isn't just the reason to use an uncoupler..

Lateral expasion stress from timber substrates can cause probs with softer stones....just thought i would add that as well..

[Ajax123]

Personally hate Chipboard Floors but I guess they have their place in the market

[bluesky]

dave are you saying i should use ditra?

[Dave]

dave are you saying i should use ditra?

It would be my preference but i would use Dural Ci as it is a lot cheaper then Ditra.

Not a lover of stone straight onto wood..

[peckers]

I agree with what dave has said "

Just to add...UFH isn't just the reason to use an uncoupler..

Lateral expasion stress from timber substrates can cause probs with softer stones....just thought i would add that as well.. "

changes in room temperature can add to lateral movement etc,
just to add to what i have already previously said, make sure there is expansion around the edges of the room between the walls and the chipboard/ply and tiles.
imo if you were to use a de-coupler then this is the better way to go and adds to the safe gaurd of a failure.
If there is room for this to be added into the budget then yes fitt it!
But as jay has said make sure there is no deflection!

[bluesky]

many thanks to all re the advice now got to break it to the client !!!

[kaharrison9]

I recently had around 40mm to make up in a hallway into the living room on a concrete floor.
After speaking with the customer we decided to make up the differance with 10mm insulation boards,ufh and slc.
Worked a treat,they got something extra for there money than just paying to build up