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This is a follow up to this question: How do I install steel dowels into the side walls of my brick bbq?

I have fit the dowels and they are working perfectly. However, the tiles on which the hot coals are placed are lifting/warping.

Here is a picture from before the dowels are installed.

enter image description here

I think the reason the tiles are lifting is because they are tightly packed together and the heat is causing expansion which leads to warping/lifting.

Apparently the tiles are heat resistant (although some of them have cracked). My parents had a similar installation and their tiles lasted more than 20 years with no lifting, cracking or warping.

How do I achieve a similarly long lasting installation? Is it just a case of using high temp mortar with more spacing in between?

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  • So are they buckling or warping? (I've never heard of ceramic warping.) Do you have extra tile (or can you procure any)?
    – isherwood
    Commented Mar 25 at 13:58
  • Did you lay the tiles and not leave sufficient time for the mortar to dry? It's another reason to fit the tile dry.
    – RMDman
    Commented Mar 25 at 14:04
  • @isherwood each individual tile is not warping, but the surface they form is warped because they are pushing against each other and have no room to expand other than up (at least this what I suspect). I probably could have found better words to describe this. I do not have any extra tiles, happy to procure new set. Commented Mar 25 at 14:35
  • @RMDman, I did not lay the tiles myself, but I also did not give it much time to dry. Commented Mar 25 at 14:36

2 Answers 2

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I want you to take a really close look at these tiles. Tightly packed tiles

Look a little bit closer. At the gap between the tiles, do you see how thin of a gap there is?

Your tiles are too tightly packed.

A lot of people think that mortars purpose is to glue tiles together. And it does that, but it has another use which is not mentioned but is just as important. Mortar is stretchy, even when it is completely 'dry' mortar is stretchy (compared to tiles). This allows mortar between bricks/tiles/etc to compress and expand as the tile expands and shrinks with temperature changes.

But in your pictures it looks like you barely have a 1/32" gap between tiles. They don't have room to shrink/expand as they warm up/cool down.

Ovens provide a very large change in temperature which causes oven bricks/tiles to expand/shrink significantly.

The fix.

Tear our your current tiles... Put a minimum of an 1/8" gap between each tile. And re grout them... It will work so much better.

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The firebrick in my wood-burner are not mortared in. They're set around the walls and held in place by a metal channel on top (which wouldn't really be necessary given the floor arrangement). The ones on the floor are just laid loose. Ash ends up filling any voids and providing some insulative value.

I'd consider two options, both of which avoid mortar altogether:

  • Overlay a second set of tile on the floor, staggering joints. Leave them all loose with small gaps at the outside of the floor.

  • Add a layer of the same firebrick we see around the walls.

One consideration is that loose tile is prone to cracking under impact. Maybe a bit of sand as a bed would help with that.

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  • Those aren't fire bricks. They are extra granite paving slabs from my garden. I only used them to prop up the grate. I have since installed steel dowels. The steel dowels are at at nice height and a second layer of anything would mess that up. So if I go with the loose fit idea, I will likely just rip off the current tiles and lay down some new ones. Commented Mar 25 at 14:39

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