LOL, I bet you guys laugh at us DIY'ers !!
It all looks so easy, till you listen to someone who knows what they are on about
It’s not rocket science, but as well as the skill involved in actually laying the tiles, you need to understand the various materials being used & their suitability/compatibility with each other. If only peeps took a little time to do some research before jumping in, it would save them an awful lot of heartache when things go disastrously wrong & expensively so in many cases.
I did lay the ply, but it could easily come up again, it is just normal 9mm stuff ontop of the floorboards !!
Screwed down every 150mm. What is WBP ? As for the joists ???
WBP is “water boil proof”; basically means the adhesive used to laminate the plies is waterproof & the ply won’t fall apart when wet. Ordinary ply does not use waterproof adhesive & applying water based tile adhesive or using it in a location which has a high ambient moisture content can cause de-lamination & there go your tiles! Sealing the back & edges prevents moisture getting into the ply which can cause warping & curling; again there go your tiles.
Some will disagree with me but 9mm ply is not thick enough for over boarding really; the min thickness recommended by BS & tile adhesive manufacturers (for warranty purposes) is 15mm but it’s generally recognised that 12mm is sufficient in most cases. This can be a problem for the door threshold height & sometimes it’s better just to rip them up & replace with 18-25mm WBP. The thickness you use depends on the floor joist size/pitch/span & the aim is to end up with a floor that has no perceivable deflection under normal loading; if deflection exceeds the spec of the flexible tile adhesive/grout being used, the tiles will fail. Someone recently posted they used the “two fat bloke test” & a piece of string to gauge any deflection. It’s important the existing boards are well secured to the joists & the overboard is screwed through into the joists not just top the top of the original floor boards but check for pipes/cables.
If you have “proper” timber floor boards in good condition & a high door threshold is a problem for you, tile backer boards may be a better option for over boarding.
95% of the walls were already there !!! Mostly plastered, with a mixture of new and old stuff (1930's probably) !!
Tile adhesion will only ever be as good as strength/adhesion to what they are stuck to so it’s very important the plaster is sound & actually stuck to the wall!
How thick is the waterproof backer ?
For walls only use 12mm (12.5mm) boards.
Should I rip out the original plasterboard and stick this stuff up ? Or can it go over the top of it ?
Personally, I would replace with 12mm waterproof tile backer boards. You can use plasterboard in wet areas but it should be tanked or you risk failure & the cost difference will be negligible when you factor in the cost of tanking. But if you have a canceled shower valve, the back of the PB will still be vulnerable in the event of a leak & could collapse from within.
You can fix over the top providing you fix through into something of substance but this will take up more space; are the walls timber stud or has the PB been dot & dabbed onto the original walls?
The cubicle has a tray so the floor won't be exposed continually and is surrounded by 3 plasterboarded/plastered walls, which were there already !
I would still tank the portion of the floor that is liable to regularly get wet & if you have a power shower it certainly will.
Do I ONLY need the tilebacker board in the shower cubicle?
You can use Moisture Resistant plasterboard in dry areas but it will depend on the tile weight your hanging & with large format tiles you must use powder cement adhesive which, along with any Gypsum plaster, will require an SBR/acrylic primer to avoid the possibility of a reaction between the cement & gypsum. If you need to plaster MR plasterboard (when ½ tiling) it must be primed or the plaster won’t stick.
What size/type of tiles are you planning to use? This will dictate what you do with the walls. For example; new bare plasterboard will accept 32 kg/sqm but plaster skim & plaster in good condition will only take 20 kg/sqm & that includes up to 4 kg/sqm for the adhesive/grout. If you’re planning large format tiles, the weight may mean you need to go to 12mm tile backer boards (mechanically fixed) which can take 55 kg/sqm depending on which one you choose.
And I am only planning on supplying the tiles to a tiler, he would supply the other stuff (adhesive, etc). If I do decide to DIY, what products are recommended and where from ?
It’s important you use quality trade products, the cheap DIY stuff is mostly crap & one well know brand sold by all the DIY sheds has a diabolical reputation. I use BAL exclusively but other good brands are Webber, Granfix, Mapei (but not the stuff sold in BNQ). Either buy on-line or fend your nearest trade tile stockist. Topps are notoriously expensive for adhesive/grout products sold to unsuspecting DIYers but you can get a trade discount at many of their outlets if you try hard enough & look the part.
