Ply floor prep...

[zzr-matt]

Ive got an 18mm chipboard floor over layed with 18mm ply screwed at 150mm centres. The ply was coated on the back and edges with sbr before installation.

Running a level over the floor some joists are up to 7mm lower than others.

I intend laying 600x300 porcelain tiles over this using granfix cfta slow set adhesive which ia good for a 3 to 6mm bed with up to 12mm in places. I fall within this spec but wonder if I would be better with a levelling compound before starting tiling or maybe skimming the hollows with adhesive first?

 

[zzr-matt]

Also should the ply be primed on the top side at all?

 

[White Room]

How many m2 is the bathroom floor.....

 

[zzr-matt]

Its 1.4m x 3m so around 4.2m2

 

[zzr-matt]

Joists run the 1.4m way so have a fairly short span if that makes a difference?

 

[White Room]

I would use a self leveling, some even go off in 3 hours...

 

[zzr-matt]

Any recommendations on one to use? I take it just fill the dips and feather out?

Worst joist is 7mm, next one either side is at 4mm out next at 2mm.

 

[White Room]

Depending whats available in your area, tilemaster is good and Ultra 2 part level....

 

[trevortine]

Also should the ply be primed on the top side at all?

In most cases no but check adhesive of choice instructions.

 

[area tiling]

Ultra's a great self levelling product !

 

[Martino]

Deffinitly spend time on the prep as this will make the tiling alot earier!...I tiled a floor that the customer self leveled himself....big mistake lol....learnt not to do that again

 

[Mark S]

I would always go with a levelling compound, it's what they are designed for, use a fiber reinforced one to accomodate any flex etc. Prime the boards first, the apply SLC.
I would suggest using 1 manufacturer for the lot, primer, leveller and adhesive, job lot, and back up from manufacturer if needed, they would even provide a spec if you rang tech desk!