I have a slate walkway that is a concrete base with slate tiles laid on top. The tiles are about 10 ins by 20 ins and 1/4 to half inch thick. There's a section of about four tiles that comes loose every year. I've had it fixed several times, but always the same group of tiles comes loose. We hardly ever get a frost. I suspect it may be related to those tiles getting very hot in the summer with the sun shining on them for a few hours, the tiles expanding and coming loose from the tiling mortar or cement that is used to stick the tiles to the concrete. What would be the best way for me to fix them?

  • Using mortar sounds like it is cracking from the expansion so I would use a weather resistant mastic some of these are a lot more flexible than bedding in mortar and may solve your problem just make sure it is waterproof. – Ed Beal Dec 6 '17 at 23:02
  • Why are only these 4 affected? Are there weatherproof mastics? Could you restick with silicon seal? Would have to be thin so there was little movement, and would have to be very even so that it gave full support. – Sherwood Botsford Dec 7 '17 at 15:22
  • @Sherwood Botsford I think these four get the direct sun for longer than the rest of the path. The rest of the path gets the sun, but not for so long due to trees providing shade as the sun moves. The four that come loose get several hour of continuous sun in the middle of the day and the afternoon, when the sun is hottest. We live in California, so there's plenty of sun. You and Ed Beal suggest weatherproof mastic, so I'll look for that. I'm not a pro, so I did not even know the terms for these kind of things, so thanks for the suggestion. – Flynn Dec 7 '17 at 19:38
  • @Ed Beal Thanks. That sounds good. I'll try it. – Flynn Dec 7 '17 at 19:39

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