Trowel size

[rj1884]

Hello. Quick question if possible please. Im starting a kitchen for which runs into a hallway. The floor is ok with regards to levels. My question is as its not completely flat should I use a notch trowel with the width 20mm and the depth 10mm half moon shaped or wil this be to much or a 10x10 square notched trowel. If neither would suffice which would you guys use.

many thanks in advance.

 

[Ian]

How much deviation is there when you put a 1.8m level down? A couple of mm or is it in need of a bit of SLC first?

 

[rj1884]

I've self levelled it and taken the lumps and bumps out of it. I'm fixing 450x450 8mm ceramic tiles

 

[Ian]

I've self levelled it and taken the lumps and bumps out of it. I'm fixing 450x450 8mm ceramic tiles

10mm square notch and backskim the tiles.

 

[wildeywilde]

"Level is desired, flat is REQUIRED".

10mm trowel is the right size. But I would back butter the tiles instead of trowelling the floor, and fill any voids on the floor using a feather edge, as you go along. Trying to build up voids with a trowel, or compensating for unflat floors using bigger trowels is a waste of time, especially with thin tiles (extra cleaning of joints etc).

 

[rj1884]

Thanks for your replies. Would you fill the voids with adhesive like you said as you go along

 

[wildeywilde]

Yes, before you lay each row, check it for flatness using a long level or feather edge, and if it's not flat, fill the voids using the feather edge, back butter the tiles and fix them down.

The quickest method in my opinion, and robust.

 

[Ian]

Yes, before you lay each row, check it for flatness using a long level or feather edge, and if it's not flat, fill the voids using the feather edge, back butter the tiles and fix them down.

The quickest method in my opinion, and robust.

If you're buttering the tiles, the adhesive won't be getting keyed to the substrate. Troweling the floor and back skimming the tiles is much better method and much more likely to acheive the desired solid bed.

 

[rj1884]

Thanks very much for your advice, I'll get some pictures up once I'm done.

 

[Time's Ran Out]

Unless you have the experience to read the floor you will find it far more acceptable to use further bags of self levelling compound to prepare the surface first! Then using the 20 mm trowel with a pourable thickbed adhesive, solid bed fix your tiles. The method described in an earlier post would not be suitable for a DIY or to give solid bed fixing over a large area!

 

[wildeywilde]

If you're buttering the tiles, the adhesive won't be getting keyed to the substrate. Troweling the floor and back skimming the tiles is much better method and much more likely to acheive the desired solid bed.

I understand why you've said that, but in fairness, you've failed to address the OP's issue i.e. that the floor is not flat. What you've advised, the normal fixing method if the floor is flat, won't solve his problem, and he'll end up with voids under tiles.

What I've proposed will definitely key (he will have skimmed the floor when he was filling the voids with the feather edge to make it flat, then would be putting down 45 x45 tiles back-buttered with a 10mm trowel, pressing firmly, and twisting).

Have a look in BS5385-1:2009, nothing wrong with back buttering...

At the end of the day, tiling onto an unflat floor is a balls ache. It is always preferable to get it flat (and level if that's a requirement depending on location / application) then fixing is quick and easy. But back in the real world, when customers won't always pay for that sort of prep, there are ways to work around and still get 100% coverage.

 

[Spud]

here you go wildey you like you tube [video=youtube;pyt2US_SSBM]http://www.youtube.com/watch?v=pyt2US_SSBM[/video]

 

[Ian]

I understand why you've said that, but in fairness, you've failed to address the OP's issue i.e. that the floor is not flat. What you've advised, the normal fixing method if the floor is flat, won't solve his problem, and he'll end up with voids under tiles.

What I've proposed will definitely key (he will have skimmed the floor when he was filling the voids with the feather edge to make it flat, then would be putting down 45 x45 tiles back-buttered with a 10mm trowel, pressing firmly, and twisting).

Have a look in BS5385-1:2009, nothing wrong with back buttering...

At the end of the day, tiling onto an unflat floor is a balls ache. It is always preferable to get it flat (and level if that's a requirement depending on location / application) then fixing is quick and easy. But back in the real world, when customers won't always pay for that sort of prep, there are ways to work around and still get 100% coverage.

He's already put SLC down so, the floor should be within a couple of mm if he's done it correctly. Troweling the back of the tile is way more time consuming than doing the floor and IMO more likely to leave voids if you haven't buttered right to the tile edge.

 

[wildeywilde]

He's already put SLC down so, the floor should be within a couple of mm if he's done it correctly. Troweling the back of the tile is way more time consuming than doing the floor and IMO more likely to leave voids if you haven't buttered right to the tile edge.

Re-read his original post Bri. He's SLC'd it, but it's not flat, hence he's worried about voids, and wondering whether to use a 20mm trowel. He's discovered what everyone knows, and that is that throwing out a couple of buckets of SLC doesn't magically make a floor level, it doesn't even make it flat. You need to go at least 10mm thick over a whole floor with SLC to get flatness and level, and 9 times out of 10 that isn't practical, or a client won't pay for the 20 bags of SLC that would be needed.

Anyway, you do it your way, I'll do it mine, and when he's finished, the OP can tell us how he did it (no doubt he'll try both and see which works best for his situation).

 

[wildeywilde]

Thanks Gary, I've seen that one. Doesn't show back buttering. Hey, you seem to like videos, so maybe you should do one with two sheets of glass, one to act as a substrate, the other a tile.

Trowel onto the substrate, back skim then fix (as per normal).

The other, skim the substrate, then back butter and fix (as I suggested to the OP).

Then look to see about coverage, and keying. You could even leave them a week then try and pull them apart etc.

Let me know, and I'll be sure to swing by and leave a nice comment... :lol:

p.s. Maybe it's a wording thing? When I say back butter, I mean spread adhesive on the back of the tile using the trowel. So you have ridges, exactly as you would have on the floor. Except they are on the back of the tile. If the floor is skimmed, then I cannot for the life of me understand how anyone could think you won't get a key??? You WILL get key, you WON'T get any voids, so what's the problem???? **yawn**