How do you get thin grout lines between paviours?

[inwood]

I need to relay a few loose internal paviours which have 'worked loose' during building work.

The grout lines on the rest of the floor are tiny (1-2mm). I'll be laying the tiles on a bed of lime (naturally!) but need to know how to grout the joints. The joints sizes are similar to what you'd see on a Viccie encaustic floor.

I was thinking of laying the tiles, waiting a day or two for the lime to set enough to hold the tiles and then dry brushing some NHL 3.5/fine sand into the joints, brushing away the excess and then lightly misting the tiles, to wet the joints.

Is this the way the joints would have been filled traditionally, anyone know how best to go about it without staining the tiles?

 

[Anne]

That might work, but if you wash off any excess lime when its still wet it shouldn't be a problem. Also could use two peices of cardboard on each side of the line so should any fall it won't hit the paviours.

 

[Andrew Bodenham]

I'm sure you know this, but if you use a hydrated lime mortar to bed your tiles it will take ages to harden up; being under the tiles the rate of carbonation will be negligible. I've not tried it myself but I'd guess that a hydraulic lime would be better for this application.

I grouted some tiles recently with a hydrate / sand mix applied wet, and it worked fine. Just make sure that you use the finest sand possible, and work the mix well in with a stick / scraper blade / whatever. A fine sponge worked well for taking off the excesss and residue. If you don't want the relatively bright colour of fresh mortar perhaps you could mix in some earth, stone dust or pigment to take it down a bit.

 

[Penners]

I defer to Andrew's knowledge on the choice of technique and mortar mix. But just a word about sweeping in a dry mix, if you still decide to do this.

Make absolutely sure that you get the joint lines properly filled up with the dry mix before you spray them. It's very easy for them to look full, but then when you wet them you suddenly get holes appearing where the mix is washed down into unseen voids.

Plenty of tapping on the tiles to cause vibration, or even packing the dry mix down with the edge of something a tiny bit thinner than the gap, is advisable.

Kiln-dried sand will also flow better than alternatives, as it's so dry.

 

[inwood]

Thanks all for the advice. Andrew - yes I was intending to use hydraulic lime. I'm presuming when you did your grouting with the hydrate/sand mix you managed to avoid staining the tiles with the lime fairly easily - that's basically what I was trying to avoid.

I'll definitely use a kiln dried sand as well.