Using lime mortar under limestone

[joe_thomas]

Hi all

I’m looking for some advice on how best to lay a mortar bed under limestone tiles.

’normally’ I’d say use a notched trowel for the adhesive, but assuming this won’t work with the consistency of the like mortar.

Just lay a continuous bed of mortar the desired thickness then tap the tile down gently?

Any advice welcome, only things I can see online are related to tile adhesive, not lime.

Cheers.

 

[Stevers]

Pads were used when concrete slabs were the norm, but these are not suitable for thin slabs/tiles of natural stone due to lack of support. Furrows (large V grooves formed with the pointing trowel) are probably the way to go to provide good continuous support, but still allow tapping down for levelling. The workability of the mortar will increase with the proportion of building sand in the mix. Sharp sand would be unhelpful if a thin bed is required.

 

[Kearn]

Mix up a weak ish NHL 2, 3:1, with some sharp / boulders sand (minimal aggregate) and fibres. Then lay it as a continuous layer as thick as required and tamp the slabs down level. You don’t want air gaps, the mix will squidge adequately. You can get away with a decent thickness to take up inconsistencies, this bedding layer was up to 40/50mm in places.

Depending on the rear of your slabs, you may need some adhesive otherwise the lime won’t adhere to a flat/smooth surface as most new cut slabs are.

 

[joe_thomas]

Mix up a weak ish NHL 2, 3:1, with some sharp / boulders sand (minimal aggregate) and fibres. Then lay it as a continuous layer as thick as required and tamp the slabs down level. You don’t want air gaps, the mix will squidge adequately. You can get away with a decent thickness to take up inconsistencies, this bedding layer was up to 40/50mm in places.

Depending on the rear of your slabs, you may need some adhesive otherwise the lime won’t adhere to a flat/smooth surface as most new cut slabs are.
View attachment 14673

Those look great!

Thanks for the replies. Looks like I'll be laying a continuous mortar bed, a bit looser than the limecrete I mixed.

I'll need to use NHL5 as that's what I have, figure that's not an issue as the slab is 5 anyway.

Cheers

Joe

 

[joe_thomas]

Mix up a weak ish NHL 2, 3:1, with some sharp / boulders sand (minimal aggregate) and fibres. Then lay it as a continuous layer as thick as required and tamp the slabs down level. You don’t want air gaps, the mix will squidge adequately. You can get away with a decent thickness to take up inconsistencies, this bedding layer was up to 40/50mm in places.

Depending on the rear of your slabs, you may need some adhesive otherwise the lime won’t adhere to a flat/smooth surface as most new cut slabs are.
View attachment 14673

Hi Kearn,

When you mixed your nhl, did you make it wetter than you would have done for a limecrete floor for example? I'd imagine a wetter mix would work better for a mortar bed as it'll be easier to work with, let the tile sink into the mortar to fill in any gaps.

Thanks.