making a garden mosaic using lime mortar?

[Becka]

Hello,

Doing up my garden at the moment, I've finally got rid of the vast quantities of concrete and asphalt and dug a pond am now sorting out my new design. In the process of digging over the garden/pond I've found large quantites of broken clay roof tiles and thought rather than send them to the dump I might do something creative with them and came up with the idea of a mosaic made with tiles and flint cobbles (also in plentiful supply) with areas for planting thymes and camomiles and the like in it to use as the base for a little table and chairs/ washing line area. Having spent months battling with concrete I'm very uninclined to use it here if i can avoid it but clearly it will need to be set in something which is why I wondered about lime mortar? is this feasible? and if it is what kind of mix etc would be required? or are there any other alternatives if that is a dumb idea?

many thanks in advance,

Becca

 

[Gervase]

Nowt wrong with lime mortar - it's been what mosaics have been set in for farsands of years.
I'd use either a hydraulic lime (NHL3.5 in the bag from Jewson's) or a fat lime with a pozzolan (metastar or brick dust, 10 per cent by volume added to bagged hydrated lime), as you'll need a firm bed for the mosaic and then a hard-setting lime cement grout for the tesserae.
You need a hydraulic lime or pozzolan because you'll end up with a fairly thick bed of mortar and much of it will be behind your tesserae - so a normal carbonation set would take months, whereas a chemical set will take just a couple of days.
Make the bed out of 3:1 sharp sand and lime laid down on a really well compacted hardcore base blinded with a thin layer of sand, let that harden and then fix the materials and grout then with 1:1 fine sand and lime.
Keep the mosaic damp while the lime cures, and when it's almost hard you can rub up the surface with a tight wad of hessian or similar to expose your tesserae and make the grouting recede a bit.

 

[DaveBrigg]

"let that harden and then fix the materials and grout"
Just checking - does that mean that the tiles cannot be set into the bed of lime? I was hoping to lay some reclaimed stone slabs outside, and was going to drop them straight onto the lime / sharp sand mix.

 

[Gervase]

Slabs should be OK, but using small pieces means that getting the final levels right can be an absolute sod - having a solid base makes that easier.

 

[Becka]

thank you, that sounds great especially as all I'd have to buy is a new bag of lime, hardcore i have in plentiful supply thanks to the concrete smashing and I've dug up tonnes of bits of buried brick so makinf brick dust should be just a matter of bashing them with something? Now I just need to come up with a good design