Terracotta tiles on a Limecrete floor

[CarolineTheChemist]

We’re currently in the process of installing a limecrete floor in our Oast house and now navigating the tricky area of finding a breathable finish.

I’ve chosen some natural terracotta tiles to go in the downstairs bathroom and hallway. They’re 20mm thick and I know they will need sealing to prevent staining.

Does anyone have any advice on what kind of mortar we should lay them on and what kind of grouting can we use to maintain the breathability??

Our builders are not experienced with lime so we will need to direct them!

 

[Cubist]

As the tiles will be laid to a limecrete floor I would suggest you use a lime based mortar for both the adhesive and grout as this will achieve a better bond to the limecrete to resist separation and aid breathability. As I understand it most tile sealants will inhibit breathability to some extent, none are absolute in my limited experience, but there are some on the market that claim the capability.

 

[88v8]

I’ve chosen some natural terracotta tiles to go in the downstairs bathroom and hallway. They’re 20mm thick and I know they will need sealing to prevent staining.

No sealing needed.
An occasional wash will be ample to keep them clean. Clean, that is, not new looking. After all, you want some patina to develop, otherwise what was the point of buying an old house ...

As Cubist has said, lime mortar for laying and grouting. NHL 5 and sharp sand, ratio 1:4.
Reason for using NHL 5 is that it goes off faster than NHL 2.

When laying the tiles, damp the sub-floor. This will aid calcification of the lime.
Leave a few days before walking on the tiles.

Then point/grout with NHL 5. If the gaps are large, use sharp sand. If small use silver sand which is a 'sharp' sand but finer. Same 1:4 mix.
The pointing must be done wet, not dry-pack. Clean it off the edges with hessian sacking as you go.

Sealing... as I have said, none required, but if you are ocd about stains then seal only the tiles, not the pointing. Not the pointing!!
Fiddly? Yes, but a tiled floor does not breath through the tiles, it breathes through the pointing.
If you seal the pointing, you might as well not have bothered with the limecrete floor.

Ivor

 

[jamest]

Your builders are likely to be familiar with regular tile adhesive, so they might appreciate something similar (i.e., not direction needed!). If so, I can recommend the Adhere Cal NHL-based tile adhesive (Mike Wye sell it, other retailers are available). It mixes like a regular, good quality tile adhesive, is nice and sticky and cures quite quickly - I've used it for sticking down terracotta on the floor and it works very well. You can grout with it too. I actually grouted mine with lime putty mortar, but that is not an approach I would recommend to anyone!

 

[CarolineTheChemist]

Thanks! I did see someone mentioned the Adhere Cal stuff on another post, so glad you've suggested it for me too.