After much thought ive taken the jump and am using dural membrne on monday for the first time. Was in buying it a couple of days ago from topps and was told, wait for it......That as long as the floor has no vertical movement in it be used instead of ply! So on top of chipboard goes down flexi addy then the membrane then tile on top so works out costing the same to tile floor with ply as to tiling with membrane. I still cant beleive it so like i said as long as theres no vertical movement and floor is bounce free ply is not required when using this and it also provides a waterproof element as well.:hurray:
Is this a dream???
Laying Durabase CI directly onto existing traditional floor boards or chip board is not best practice and its certainly not a substitute for ply
Traditional floor boards : If newly laid will expand and contract hugely at initial warm up and further during temperature changes within the home. Movement across the surface of a floor can be huge without mentioning curling which will create unsatisfactory conditions. Old floor boards do not move at the same rate as new but never the less move especially with new heating systems. These boards will generally already be curled so when laying a decoupling membrane you will have indifferent points of contact.
Weyroc / chipboard flooring : Constitute board manufacturers use waxes during manufacture which creates a closed surface and during heating and cooling the waxes can release. Chip boards are also subject to curling creating an unsatisfactory surface.
You will also be hard pressed to get an adhesive company to admit any liability tiling onto weyroc.
What are you starting Doug,LOL
My ideal is going to be,
1. Ply floor no matter if there floor boards, chipboard etc everything but screed
2. Lay mat on all floors no matter of tile type using flexi addy (powdered flexible / 4mm mosaic trowel)
3. Lay tile onto Dural using flexi addy
4. Grout and done...
This is the correct way to tile a wooden or suspect floor using an uncoupling membrane.
When you overply a floor you are :
Strengthening the sub floor by increasing its thickness
Tieing together the boards below so you new floor becomes the subfloor
Creates a stable flat surface for tiling to bridging any curling
Reduces greatly the movement points ie joints between boards
Has a tileable surface
( All the above assumes screwing at 300mm centres or less to a sound subfloor)
Hi DavieA,
Your scenario is ideal, however, I think you may end up pricing yourself out of work due to over-specifing.
I use a decoupler for natural stone, regardless of substrate. For most ceramic and porcelain I just make sure that the floor is deflection free.
You need to asses each job and weigh up the possibility of lateral movement and, therefore, the use (or not) for a decoupling membrane.
IMO, there is no hard and fast rule for a decoupler, just common sense and risk assessment.
Hypertheticaly we can all use risk assesment and common sense but at the end of the day best practice is what covers you when you travertine gets torn...........
by installing backer boards onto ply only means that there is a more stable surface on which to tile...
the joists, ply/chip board, and backerboards on top, will/can still suffer from lateral movement,therefore, the decoupling membrane does a completely different role and protects the tile against lateral movement....
in short...
no matter how thick your joists and ply are, they can still suffer lateral (side to side) movement due to the joists lying on the inner skin of the brickwork of a wall...walls contract and expand continually throught the year, intial drying out process, ground movement and weather/temperature changes..
if you put backerboards onto ply, then this is not a substitute for a decoupling matt, its simply a more stable and compound surface in which to tile upon...
as mentioned in previous posts, deflection (up and down) movement, is a different movement than lateral (side to side) when you realise that, the decisions become more straightforward...
cheers
ed
This is not strictly true as structural movement would shift the whole plain which is effectively the same as vertical deflection, its reliant on mechanical movement. Lateral deflection / movement across a surface is the result of environmental factors generally from the heating and cooling process which cause expansion and contraction of materials, wood in this case.
Your point about cement boards is valid using cement boards can increase the points of potential fracture due to their size as opposed to ply. (unless you put them over a seperation membrane of course) Using them over ply is a waste of money
A few points to think on guys..........
