I'm laying 2" x 2" tiles over a raised concrete patio slab that is 11' 6" by 16' 1 1/4". The tiles come in 12" x 24" sheets with the individual tiles joined by little blobs of a rubbery substance. Across the width of slab I think it will work out nicely. But going the other way I've got to either make the slab 3/4" longer or gain 1 1/4" over the 16' 1 1/4" dimension. If I put the extra space between the sheets of tiles that works out to adding about 1/16" (1.2 mm) between each sheet. Since the tiles are spaced 1/8" (3 mm) apart in the sheets this seems like it would result in a noticeable difference.

So, I'm wondering how large a difference would be noticeable? For example if I cut the sheets apart in the middle, I could increase every third by a bit more than a 32nd of an inch. Would that stand out?

  • Just cut 3/4" off one side, or 3/8" off both sides.
    – Ecnerwal
    Aug 12 '15 at 2:55
  • I think I would notice the difference and it would really bug me, so I was hoping to not have to cut tiles.
    – dlu
    Aug 12 '15 at 4:51

To put this in perspective, with my current browser settings, 1/32" is only slightly wider than a capital 'I'. It's narrower than a piece of aggregate in sanded grout.

Consider the following (scaled as 1 pixel = 1/32"):

Scaled tile layout

Can you tell at a glance which gap is a pixel wider? Keep in mind that it's even less perceptable with lower contrast. How about this one?

enter image description here

Do a dry layout and have somebody else (preferably somebody who doesn't know about the spacing) look at it. I'm guessing it isn't going to be noticable at all. Truth be told, even a fantastic tiling job isn't going to maintain spacing tolerances of 1/32" on any consistent basis.

  • 1
    @dlu - Messing with the spacing happens a lot more often than you'd think, especially when tiling walls or floors that are badly out of square. It usually ends up making it look more square.
    – Comintern
    Aug 12 '15 at 5:05
  • I'm sure – I also suspect that there is quite a bit of art to it. Years ago I worked on a job in NYC that had white tile everywhere and we weren't allowed to cut it. I was very thankful that I only had to make the electrical work.
    – dlu
    Aug 12 '15 at 5:19
  • Awesome visual. Very helpful to get the concept across. This feels good to know, might make the difference between needing to run an extra single column of tiles, or evenly fill an odd sized space! Aug 12 '15 at 13:40

Note that the math is not that easy. You have a HUGE surface compared to your tile size. Even coming in sheets you will have natural variance - even between tiles on the same sheet.

The side that you have calculated out perfectly may end up being right in the middle of a tile. That is unless you do the following:

  1. Plop down your thinset for the one row where you think your tiles will line up across exactly. So let's just say you are doing the bottom of the patio.
  2. Set all of your sheets for that row.
  3. Go over the sheet spacing. Maybe everything works out maybe it doesn't. At the very least you can move the sheets before they set. (you may have to cut a couple sheets mid sheet)
  4. So now we have the bottom laid out and spaced evenly with no cuts. Now we will do one of the sides. So spread your thinset going up the right side for one row.
  5. Follow the same principles of setting the tile and then lining up your tiles evenly based on your endpoints.
  6. Fill in the rest of the patio based on your initial "L" baseline.

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