Trowel Size vs Adhesive thickness

**gontarek** · 19-09-2009

I am trying to figure out how much adhesive I going to need for my floor. I though this was simple (and maybe it is), but I am wondering how you work this our for a given trowel size

If I use a 12mm notched trowel, I am presuming this is not 12mm of adhesive thickness as I am presuming the ridges spread (which I guess is the whole point) - so given a 12mm notched trowel, what is the actual depth of adhesive used (is it 6mm for example ?) ? And is this the figure I should be using when calculating coverage when a manufacturer (e.g. Mapei) indicates a figure of kg/m2/mm for their adhesive ?

Also is there any significant difference in that figure between a square or a rounded notch (I would guess the rounded uses slightly less adhesive, therefore a thinner overall layer)

I 'm laying opus pattern which has a majority of 600x400 & 400x400 tiles, so from everything I've read it is the 12mm trowel I really need.

I tell you what though - the last few weeks have been an education or what ! Here I thought I would 'simply' just lay some tiles across our new extension and kitchen and this forum would answer a few questions I had. I just didn't realise how involved it all is! I've now learned about substrates, floor strengthening, decoupling membranes, expansion joints, different grout and adhesive types, tile sealing and now trowel sizes ! I can see why one would think of hiring a pro for this - shame I can't afford one

BUt having said that this forum and the people on it have been a godsend - thanks folks!

**pjc** · 19-09-2009

well how long is a piece of string lol i lay large format tiles and use PTB if I get 2 sq mts a 20kg bag on a good floor i am well pleased but you should get better on SPf or would suggest you using slow set will give you more time only if you are going onto screed i think you will be best to start it after using a few bags you should be able to get some idea :Pete