Stonemarket horizon sandstone - Client choice

[Rich H]

I have a new client that wants a 100m2 patio laid with Stonemarket Horizon Sandstone. At first glance, they look like tiles which are butt jointed, so I was thinking I would lay them on a screed bed. The mechanical spec though states 18-22mm thickness, so I think the screed is out the window. Individual bedding with these 'tiles' would be a right pain in the neck.

Anyone laid this stuff before or similar with any tips for a swearing-free job?

[lutonlagerlout]

no such thing as butt jointed rich
5mm is minimum
make sure your supplier has got them,i needed some capital sandstone from stonemarket last year but they had stopped doing it
LLL

[Tony McC]

Check with StoneMarket because I seem to recall that Horizon was one of the products they planned to offer only as calibrated, so a screed bed would be ideal.

Don't butt-joint: ensure you have AT LEAST 3mm between each unit otherwise they'll move and they'll spall on the arisses, which is the very last thing you want with this honed sandstone.

[Rich H]

Yes, sorry they are 'laid with minimal joints' on closer inspection. They also specify the use of white cement for the bedding course, by christ. Wouldn't think that's necessary with a sharp sand mix, but that's the spec.

The horizontal cuts are calibrated - they state them as exactly 480mm x Xmm - but the thickness is stated as 18-22mm. I think I'll take your advice and check, it'll be a hell of a lot easier than individual bedding with these tolerances - especially over a 25m run!

Thanks for the feedback, lads.

[bhwh]

Rich

I am just about to lay some of this and quite unsure about the best method of bedding. How did you get on in the end?

Cheers

Ben

[Rich H]

Haven't done it yet. A couple more weeks of ground works and prep to go yet. You can be the guinea pig!

I called Stonemarket and said I wanted some technical advice on jointing, was on hold for an eternity and the very nice lady that answered in the end wasn't someone who could help with technical points. She said she would get someone to call me back. They didn't.

[bhwh]

Ok. Having chatted with guys on diynot and re-reading stonemarket technical docs, I'm going to go for an individual dryish mortar bed with white cement. But then I've quite a bit less than 100m to do!

I'll let you know how things go.

[Tony McC]

I suspect the thinking behind the requirement to use white cement is that they expect the flags to be laid on a wet mortar, which would carry cement particles into the body of the flag and possibly cause 'picture framing'. This would still happen with white cement, but they seem to think it would be less noticeable than if it were standard 'grey' cement. I'm not so sure.

However, if you are using a semi-dry bed, or even a moist mix, the risk of picture framing is dramatically reduced and I'd be less inclined to use an over-priced white cement, especially if I was planning to use a polymeric jointing product.

I know some of the tech s'ports at Stonemarket: I'll see if I can get a reply for you, or at least an explanation for the white cem.

[bhwh]

Tony

That's a very kind offer. Any tech advice you can get would be appreciated.

As a relative novice, I understand the thinking about white cement and pic framing but hadn't realised yet that there is a considerable price difference between white and grey cement.

I look forward to any feedback you can give. By the way, I'm starting to lay on Monday...so I hope I make no errors in the meantime. The stone has cost near £500!

[Rich H]

I think the cost for my little lot will be about £3800! The slabs are more like tiles really, at 18-22mm thick, so I can see the worry with a soft sand mortar bed. I'd always use a sharp sand mix in any case which has little or no colour anyway. As for picture framing, I reckon if it happens it will happen whatever cement you use!

[bhwh]

Ok Rich so is a bit more than me!

Started yesterday...only thing I need to watch when working today is that any excess mortar that gathered in the joints has created a bit of pic framing effect as it dried. So i'l be careful not to let this happen today. And that is with using white cement also!

Cheers

Ben

[Rich H]

After speaking to Stonemarket I opted to lay on a semi-dry sharp to mastercrete mix of 4:1, individually laid with typically 70-90mm bedding course over existing concrete and new very well compacted Type 1 of 100mm over chalk.

Stonemarket would not give me a recommendation on jointing. They were worried about colour from a polymeric leaching into the slab edges (??) and when I said I thought the joints were too narrow for it anyway he said, "oh yes, you need 3mm for the pattern to work." The only solution seemed to be KDS so that's what I've done.

The calibration can't be too good, as there is quite a variability in slab size, +/-2mm at least, and sometimes different dimensions on opposing edges, requiring repeated string line set ups. The thicknesses were highly variable (despite being told that all the slabs in a given crate would have been cut the same) which slowed down the laying a bit. Lastly, there were many rejects, not because of natural flaws but because of indelible staining or rust spots.

Anyway, you be the judge. Haunching on the radii still to do, of course. I'd be interested to see pics of Ben's job.

[Tony McC]

Bollocks you need a 3mm joint! They can be laid with a 10-12mm mortared joint no problem! In fact, I think they'd look better with a wider joint because that would emphasise the individuality of each flagstone. Close-jointing, especially when used with soft-coloured stone flags, tends to create a homogenous-looking pavement.

Still, it looks grand in those photies.

[Rich H]

Thanks, Tony. It was the homogenous look the client was after. He was actually a little disappointed that they look, to him, so variable!

[lutonlagerlout]

nice work there rich

and

Ok. Having chatted with guys on diynot

from bhwh

it is heresey to mention that forum on here mate,next thing you will be buying tommy "5 spot" walsh's book

i asked a simple plumbing question on there once and the response was patronising in the extreme. stuff 'em

LLL