Indian stone and leaching (again!!)

[docb]

Hello All

I am planning on laying 40 m2 of 22mm sawn teakwood Indian stone over the weekend.

the stone has been delivered, and the first few off the pallet show that the stone is highly porous.

the stone has been purchased for its look, being contemporary and possibility for tight straight perfect joints.

I am now really concerned abot leaching/picture framing. I was going to use a semi dry mix, screeded, but have a read a few people on here recommend a moist mix, due to better adhesion to the underside, and ease of laying.

Will a moist mix give me problems from leaching? My life would be a living hell if the prize slabs, purchased for their colour and appearance, were stained in some way.

Also i am assuming that there will be no way to run a plate over a moist mix, so with no compaction, how is the moist mix a better option than a semi dry? isnt it more likely to drop over time?

Is the moist mix a "lay by slab" rather than a screeded mix?

thanks in advance

Doc

[London Stone Paving]

Doc

Teak wood is a very soft stone which is better suited to carving than paving. First of all you cant really use a screed for this material, the slabs need to be laid individually as you rightly pointed out.

How thick is the material? I'm guessing it will be 20-22mm. In my experience the dryer the mix the harder you need to hit your slabs to get them level and also to compact the bedding layer sufficiently.

You are better off going for a wetter mix which will take a lot less force to compact it and get the slabs level. Dont worry, it wont sink as long as you put the right quantity of cement in and compact it properly.

On to the leaching. The softer the stone is the more chance of leaching. We recently laid some Portland limestone at our display and its been completely ruined by leaching. Using a wetter mix will increase the chance of leaching but in this situation you need to use a wet mix. If you apply an SBR or some kind of bond bridge to the underside of the stone this should stop any leaching.

PS Easipoint is better than Romex for this job if you want a contemporary finish

[docb]

great stuff, thanks LSP

the slabs are 22mm. i will try and seal from the underside with some SBR. just another question, but the SBR wont leach through will it?

thanks again

Doc

[DNgroundworks]

but the SBR wont leach through will it?

Nope

[docb]

good grief, that stuff is expensive....

is it all the same stuff, some vastly different prices around

can it be watered down for sealing the underside of slabs or does it have to be neat?

[London Stone Paving]

Dont know but I am sure somebody will check in soon who knows the answer

[lutonlagerlout]

we pay around £16 for 5 litres
i dont seal the slabs with it but i do add it to the wet mix about 100ml per mix
i find it adds a lot of adhesion for not much money
LLL

[docb]

OK bit of an update,

had a bit of an experiment over the weekend. watered down in 5:1, 2:1 and neat on 3 different slabs.
then put a soaked grit sand bed down on a soaked board, and dropped the slab on top and tappped down a bit to get most of the back of the slab in contact with the soaked sand.

unfortunately both the 5:1 and the 2:1 didnt stop the water pulling through to the top. the neat did (as expected)

I am going to try 1:1 tonight.

LLL, I appreciate for adding to a mix you wont be using much, and therefore it is a small amount of additional cost compared to the result you are after. but i need to seal the backs of 40m2 of paving, which is going to eat up quite a lot of the stuff.

thanks again for all your help

Doc