Laying basalt patio - special tips?

[Confused.com]

Hi all

Having read several posts/horror stories here about the special precautions required for laying and pointing silver/graphite granite pavings slabs, I was wondering if the tips provided apply equally to their darker, more dense geological cousins, basalt?

The slabs I am contemplating are sawn, 25mm thick and flame textured.

Thanks

[London Stone Paving]

Great choice of stone. Basalt is hard as nails and in my experience because of its cost, is always cut accurately.
No special precautions are required. Usual installation method.

Full bed

Bit wetter than semi dry because its such a dense stone so you want to ensure a good level of adhesion

SBR wouldn't do you any harm with this product. 100ml per mix and properly mixed/diluted in a bucket of clean water before being added to the mix (credit mick g)

Gaps 6-8mm

Clean up any mortar spills straightaway

Happy days, its a great stone

Steve

[lutonlagerlout]

sorry but i disagree with adding SBR to the water

we always add it to the mix as that way you are certain of 100ml in every gauge

if you add it to the water and the sand is a little wet (like it is right now) then you may only use half a bucket of water

so only 50ml

also at the end of the day noddy the hoddy has got a bucket of water with SBR in it and no where for it to go

why they do this I have no idea,same as 3 bags of cement being open simultaneously

but anyway we find better to add to the mix

cheers LLL

[mickg]

>>>>at the end of the day noddy the hoddy has got a bucket of water with SBR in it and no where for it to go
not if noddy the not right uses his pea brain and thinks I best not pour any more SBR into a bucket because I dont need to mix any more today - not rocket science is it ???

also common sense prevails, if the sand is wet through then we change the mix accordingly and not by choice but glug glug into the mixer

[lutonlagerlout]

we like to try and *keep it simple* for obvious reasons

the last hoddy we had thought it would be a good idea to gauge mortar dye by adding it to the water

you can guess the rest

LLL

[Confused.com]

Cheers everyone. Can I just check jointing material though, as I see one large supplier/manufacturer of granite slabs specifically says NOT to use their proprietary brush-in pointing with their granite range.

Again, is this just the lighter granites and their particular mix that are incompatible and cause picture framing or a wider no-no on using brush-in with this family of stone?

Thanks again

C.com

[Tony McC]

I'm fairly certain we've discussed this before. The lighter granite to which you refer is the G603 silver grey, sold under various fancy names by all sorts of suppliers, and it is notoriously porous, so much so that it actively sucks-up the resin binder from polymerics and slurries and creates the unsightly 'picture framing' effect. It can do the very same thing with cement mortars. On the most porous pieces of G603, the surface of the paving can also absorb the resin which can result in unsightly darker patches, varying with the natural porosity of each part of the stone.

There have been various attempts to forsetall this effect. Pre-sealing the granite to prevent or limit absorption of the resin is a popular tactic, but has limited success. Whenever a piece of granite is cut, the 'seal' is breached and the resin can get into the granite. Also, with *some* mortars, particular sealants prevent a really good bond between mortar and stone.

Generally speaking, by thoroughly soaking the stone prior to jointing, and I mean soaking to and beyond saturation point, the thirst of the stone is quenched and less resin (or cement paste) is absorbed, which in turn prevents or minimises the dreaded picture framing effect. It also acts against surface staining, but because we are dealing with completely natural materials, with unpredictable porosity, results can't be guaranteed. This is why many contractors opt to use a dry-ish, just-about-damp cement mortar to hand point G603

[John156]

Laid Black Basalt two or three times. No problems with picture framing from my experience. I've laid it with and without SBR in the laying Course. Always with a wetish mix. I've used sand a cement and an external grout which I think was cement based with no problems. To be on the safe side you could include SBR in the mix but just be clean when your laying to avoid stains.

[Confused.com]

Cheers john and of course Tony - I feel a bit less confused.

One further question though as I have seen this quoted in John's reply and sporadically on this site but never knew why: "EXTERNAL GROUT" - what's the deal versus the sand/ cement versus brush in epoxy based stuff and why should basalt warrant its use?

Or have I missed Tony's page on this somewhere?!

[John156]

I only used an external grout as Client and I wanted a certain colour and the joints were very thin. External grouts are normally made up of very fine sands. Another time we used fine sharp sand and cement which we always use. Both times had no issues. Hope this helps.

[Tony McC]

Basalt paving does not necessarily warrant the expense of a quality resin slurry grout. If you or your installer feel confident using a cement mortar, then there's nowt wrong with that. Resin slurries are great for surfaces that would be tricky to keep clean using cement mortars or for when the surface just never seems to dry out because of the weather.

There are quite a few pages on the main website looking at resin mortars and their potential advantages, but I'd suggest this one gives a reasonably comprehensive overview.



Edited By Tony McC on 1393091790

[Confused.com]

Couldn't be clearer than that. Thanks again one and all.

[rash]

Hi Tony et all

It's been a while since I was on here last (Aug 2002 to be exact!) ... a house move, two kids and a home extension in progress have now brought me back

I'm having some work done to the rear and side of my property and for a new patio we've been taken by the look of black basalt paving - thinking of getting the plank paving style.

Is this product quite forgiving in the way it's laid? At present, I'm thinking of asking my builder to lay the patio at the end of the house build project as it was included in the quote as part of my build ... but I'm a bit wary after reading this post. I'm no paving expert (and I don't think my builder is either) but would a competent person be able to lay without too many issues ... or would the advice be to get a specialist in? ... or dare I attempt to DIY ?!

Also, on a side note - we're looking at an area of 30m2 ... how much would it cost to get something laid of this size in the London area - i.e. what are the current expected costs for all the MOT, mortal, cement, additives, laying etc that go on TOP of the cost of the slabs themselves - I know it's a ridiculous thing to ask but any rough figure would help me out here!

Great to be back - and even more to find that this place is still alive and buzzing! :p

[lutonlagerlout]

ballpark £100 per metre +flags
LLL

[Tony McC]

Don't, please don't let the builder balls-up the basalt. Strongarm him into bringing in a tradesman.

He wouldn't have done the lectrix himself. and he may well have brought in a plasterer, so make sure he brings in a specialist to lay your relatively expensive paving.