Should you use silicon or grout around outside patio tiles?

nieldy

Hi, we have just had our outdoor patio re-tiled with new tiles after we had a significant water leak and quite a large area of tiles were destroyed trying to locate the leak. The tiler has done a good job from what I can tell, but I wanted to check about his use of silicon around the edges (pretty sure it's silicon by the feel of it).

Initially I had asked if he could use silicon or caulk around the edges of the tiles where they meet the brick wall, because I read that was a good idea (mainly from AI search results TBH).

But, then I talked to him later and he suggested grout normally looks better and the also the previous tiles had grout on the edges. So, I said to go with grout instead.

But now that the job has been completed, I can see he used silicon… probably he forgot the last conversation.

I've searched on this more, and there seem to be mixed views on grout vs silicon for outdoor tiles against brick.

Just wanted to get another opinion (and hopefully reassurance) that what he's done is ok. I do think grout would have looked slightly better, but the silicon is colour matched and doesn't look bad (see photo below).

I guess I just want to check if this is something worth raising, or if I should just let it go.

Cheers,

Stephen

EricL

Hello @nieldy

From what you've described (and from the photo), I actually think this is one of those situations where the tiler has probably made the better technical choice, even if it wasn't what you last discussed.

The joint where the tiles meet the brick wall is what's called a change of plane. The patio slab and the brick wall will expand, contract and move slightly at different rates as temperatures change and as the ground moves over time. Because of that, a flexible sealant (silicone or polyurethane sealant) is generally considered best practice, especially outdoors. Grout is rigid, so it's much more likely to crack or separate along that joint eventually.

Looking at your photo, the bead appears to be neat and consistent, the colour match is quite good, and it blends in well with the surrounding tiles and brickwork. While grout may have looked a little more seamless initially, there's a reasonable chance it would eventually develop hairline cracks as the wall and tiles move independently. A flexible sealant is much better able to accommodate that movement.

The only caveat is that it should be an exterior-grade, UV-resistant, neutral-cure silicone (or an equivalent flexible tile sealant) rather than a basic interior bathroom silicone. Most professional tilers will use the correct colour-matched sealant for this type of application, so I wouldn't be overly concerned.

Overall, I don't think this is something I'd be raising as a defect. In fact, from a durability point of view, it's arguably the better finish. The patio looks like it's been finished neatly, and I think you can feel pretty confident that the silicone around the perimeter was an appropriate choice for an outdoor tiled area against a brick wall.

If you need further assistance, please let us know.

Eric