Thanks for
Thanks for your reply. Which sheet timber should I be using to make up the difference? Or does it not matter?
How would you recommend securing the sheet timber to the concrete underneath? Or can it just be placed on top?
Thanks again
Sheet timber will be quicker and cheaper than laying SL compound at that depth (around 1cm ?), just depends on the exact height you need to make up and sheet material thickness availability
Look at chipboard, OSB, shuttering ply as examples, OSB readily available at 9mm, and buying 8x4 sheets will work out best value - look at a local woodyard for prices and delivery if needed
You don’t want any movement between sheet timber and concrete floor as can lead to noise as timber flexes
How flat is the concrete floor ?
If like a snooker table, then lay sheet timber, drill, plug and screw into concrete floor - consider possibility of pipes and electrics being buried in floor before drilling ?
If dips and hollows and not perfect, SBR diluted @ 1-4 with water, brush over concrete and sheet timber, allow to dry
Then a thin screed of tile adhesive over complete floor, using a notched trowel, using a powdered adhesive you mix yourself to take out dips
Lay sheet timber into wet tile adhesive and level, again, drill, plug and screw
Need to check finished level constantly to make sure your on track with existing floor, this can be adjusted with tile adhesive bed thickness or set sheet material couple mm lower and finish with SL Compound (but you won’t need nearly as much this time)
Whatever method, prime top surface of sheet material with SBR prior to pouring SL Compound
Mapei Ultraplan is a good product, fibre reinforced and flexible, needed if going over any timber
If just pouring over concrete, then look at Mapei Ultimate, cheaper and used for slab floors
All probably more work than you was expecting
