I have an above ground exterior concrete slab that we'd like to surface with 2" x 2" porcelain tiles. The slab is just a little too small – about 3/4" in one dimension. I'm wondering if it would work to build a form around the short end and pour in the missing 3/4" of concrete? I don't think it would be possible to accommodate another full tile (e.g., to add 2 3/4" rather than just 3/4").

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    Related. Also, my answer here, describes how to reinforce it with Tapcons instead of bar stock. Another option is to cut the tiles. – Mazura Aug 12 '15 at 1:33
  • My hope is to not cut the tiles. I've got about 16' so I figure I could mess with the gaps between the tiles, but I'd rather not… – dlu Aug 12 '15 at 1:58
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    Assuming 2" tiles over a 16' span, you can make up 3/4" by adding just .2mm to each gap. Wouldn't be noticeable in the least, even if you were looking for it. – Comintern Aug 12 '15 at 2:05
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    The problem is that the tiles aren't 2" tiles at that level. They come in sheets that are 12" x 24", so I think I'd be looking at making the gaps about 1.2 mm smaller between sheets. The gaps between tiles on the sheets are roughly 3 mm (1/8") so I think that would be noticeable. – dlu Aug 12 '15 at 2:19
  • Are you sure those tiles are OK to use on a slab / floor ? Seems like it would be tricky to get enough mortar down to hold them without it coming up between them. I ran into that using 1 in glass mosaics on a wall. sorry for not answering the question. If you reinforced the joint and used an additive to make sure it sticks, you could probably expand the slab that much. – BrianK Aug 14 '15 at 4:14

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