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Watching videos on tiling. I have small (4 inch square tiles).

I see some installers putting thinset on wall and no thinset on tile - just press to wall. That's difficult because the space is very tight. Have to use small bucket and trowel. Large swipes on wall is not possible.

I see some installers put thinset on the tile and none on the all. I would like to do this. It's easier.

I see some installers put thinset on wall and tile. I'd prefer not to do this because of the space constraint.

Does it really matter if the tile is small and I'm sure the bond is complete?

Update: I ended up using all three methods depending on space constraints. Very small bathroom. Talavera tile, some curved areas and outlines, various tile sizes-some like mosaic, etc. I just made sure there was enough mortar to adhere. It was very slow.

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  • Aside from personal preference, perhaps it depends on "straightness" of the wall - glue can only make up so much thickness ...
    – Mr R
    Feb 10, 2023 at 21:35
  • The main issue with back-buttering is getting a consistent amount on each tile. If the amount on tiles is different, the installed height of those tiles will be different (so the surface of the tiled wall won't be flat.)
    – Ecnerwal
    Feb 10, 2023 at 23:00

5 Answers 5

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Any of those methods should work, so use whatever's the most convenient.

  • On wall only: this is the fastest way to cover large areas, so that's what people usually do.
  • On tile only (a.k.a. back-buttering): takes more time, and not practical for very small tiles. But sometimes it makes sense.
  • Both tile and wall: I'm not sure what the point is, but it should be OK as long as you ensure you don't wind up with too much mortar.
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The most important is to have enough thinset behind the tile to ensure proper adhesion over most of the surface. This can be achieved with both methods (thinset on wall or on tile), as long as the comb trowel's teeth aren't too small.

How much thinset to use depends on the flatness of the wall, a flatter wall (drywall) requires less thinset than something rough like brick. However when applying thinset on the wall with a large trowel, it will automatically put more mortar in the holes and less on the bumps, which is nice. Buttering just the tile doesn't do that, if you butter a tile and stick it on brick it'll just fall off, so it's best to do it only on flat walls.

If you're laying small tiles on drywall, even if you don't need waterproofing, you have to mud the drywall joints before. With large tiles it can be skipped (although that feels cheap) because the tile is much wider than the thinner part of the drywall at the edges, so it will bridge the gap... but with smaller tiles, the one that ends up with its edge close to the edge of the drywall will end up sticking out.

Applying thinset to the wall also forces you to actually look at the wall and feel it under your trowel. If you butter only the tiles, you should skim the whole wall with a trowel first to check for bumps or leftover bits of plaster or mud that stick out and will turn your tile into a see saw. There's always something, and it's much easier to remove when it's not buried in mortar.

To butter small tiles it's easier to put them in a grid on a table with the edges joined and apply the mortar on the whole bunch at once. Otherwise you'll end up buttering both sides. Then swipe a sponge on the edges before putting the tile on the wall, because it's much easier to remove extra mortar when the edges are accessible, rather than later when you only have the width of the joint to work with. Also you need several sponges and buckets, because you will spend a lot of time cleaning mortar off your hands (and everywhere else). Buttering the tiles tends to be a lot messier than just the walls...

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Both methods will work, but they depend on your skills.

On the wall is easier and the whole surface of the tile will adhere.

On the tile the typical problem is not to have uniform and not enough mortar at the edges of the tiles, without contaminating the front of the tile.

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"Back buttering" the tiles will work perfectly fine... I've done it MANY times for a variety of reasons and never had a problem

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  • I suppose it depends what one means by "back buttering." OP seems to want to use a notched trowel on the tile instead of the wall. To me, back buttering is spreading a thin flat bond coat of thinset on the tile, with notched-trowel thinset on the wall (substrate).
    – Huesmann
    Feb 11, 2023 at 21:08
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I’m with Huesmann. Back butter to me means thin coat. I always apply the thinnest coat on larger tiles and I’m not against doing it on 4” or 6”. And mortar rake the walls/floor. It far outperforms one on either. The super thin, wet and level coat sucks up to the mortar coat. You won’t be sorry you did it and it doesn’t have to be messy.

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