Newbie laying sandstone patio

[indianjoe]

Dear all - some advice would be much appreciated.

Have read quite a bit but am still going round in circles a bit.

I am laying a 30m2 patio using 600 x 300 x 22 sawn polished rainbow indian sandstone.
Have already laid hardcore base and whomped this flat. Next step is sand/cement base. arranging slabs.

I'm wondering what to use for jointing. The slabs are only 22mm thick & I'd like nice thin joints. If I use a normal sand/cement mix my understanding is I need a reasonably wide joint 8-12mm? So I was looking at using Rompox or NCC compounds as I though these would allow athinner joint but also save money as the slabs are small and there are a lot of joints. A mate of mine is laying these and although he's got a lot of building experience he's not worked with sandstone or these compounds before.

I've read that the min depth is 30mm for these - is there an easy solution to getting thin (3-5mm) joints i.e. a compound you've used that just works (if base & stone put down) and just jointing to be done.

I don't want to rely on newbie instinct but I was imagining simply digging out 8mm channels in the base to give the 30mm depth - or am I missing the point?

 

[Nige F]

have a look at www.pavingexpert.com

 

[r896neo]

He should be laying them on a full bed of wet mortar between 25 and 50mm deep so the easiest way will be to rake out the joints the day after laying while the mortar is dry but still not too hard.

To be honest the gtfk or other slurry types can be applied to smaller joints fine, the rompox easy, marshalls weatherpoint and other brush in and strike types don't work as easily with joints under 10mm as its harder to strike, i would imagine they are also a little more depth sensitive.

Really raking the joints is an easy process and will only take an hour or so on 30m, then a quick blast with the leaf blower to clean out the loose stuff, or just brush it carefully. Make your self a few bits of wood with a screw 30mm protruding through the end and that is perfect for raking out.

Jointing compounds have really come on and for easily stained natural stone they not only look better than mortar due to their colour but are so quick to use in comparison to conventional pointing. In a professional context they really make sense cause they save so much time but for diy they are pretty dear and you could easily spend 80-100 quid for 30m but it will only take 30 mins as opposed to normal pointing where the materials cost buttons but it could take a long day.

 

[indianjoe]

Wonderful! thanks guys - great tip with the DIY rake - will do that.

I had been having a good trawl through paving expert and it has been brilliant at getting me 95% there but it was the confidence in that last 5% as I get to the 'right now are you sure you wan me to lay these 3mm apart?'

I totally appreciate the 'false economy' bit and will buy 50kg of compound at £120 rather than spend 4 times that on labour for conventional pointing.

I was also a little nervous of staining the stone.

I'm down to two GTFK products the VDW840+ or the VDW 805. But have also noticed something called 'SIKA block paving fix' which claims to be suitable for all applications - has anyone got any knowledge of this?

The other complication I've got is that the stone needs a bloody good wash. I mean pressure wash with a patio attachment, as it was left outside for a while and the are marks that are only coming out at pressure.

I'm thinking that the best time to do this is pre-jointing once the raked bed/paving is down and gone off, as this will clean the stone and get rid of bits in prep for jointing. -This shouldn't affect a solid base should it?

So, the chain of events now is bed in gutter, lay sand/cement base on hard core, coat back of stone with slurry, lay stone wait 24hours, rake for depth , wait 5 days or so and pressure wash, dry over 48hours and then joint with GTFK compound - then seal with Resiblock colour restorer.

Again- thanks for the help.

 

[r896neo]

Personally i don't bother with the slurry, i don't think it is neccessary and i lay on 5:1 plastering sand : opc with no problems.

Apologies but re reading your post you want to lay these with a tight 3-5mm joint? That will not work and will need to be at least 8mm or so as the variation in size and shape of natural stone will make it impossible to go smaller. If you are using a random pattern of 3/4/5 sizes it will be even worse as you will need to even out the joints as the bigger flags are say 600mm wide so 600mm plus a 10mm joint is 610 but if you then lay 2 300 flags along side you have 2x300 plus 2 x 10mm so 620 hence the bigger joints.

Sorry i didn't pick that up before. Steer clear of the sika product and go for the gtfk, rompox or marshalls weatherpoint 365.

 

[indianjoe]

Thanks for the info - stone is calibrated so all dimensions are spot on, they are like wall tiles! 600 x 300 x 22, polished with completely straight edges. Had them stacked after giving them a brush down before laying and they are perfectly lined up - no bevel in the edges at all.

This means that the joints can be a tight & equally spaced, purely from a pattern PoV. Have alread gone for 3mm, fingers crossed this will be ok. If physical dimension uneveness is the only reason not to go this small, then I should be ok. If there is a chemical setting reason, I'm screwed.

Is the Sika stuff really that bad? I'm sure there is a reason that it is £20 a tub opposed to £65-75 for GTFK and also that NCC stock Sika but not this product - but was just wondering what the exact reason is? Have you used both and GTFK was just noticeably better all round for using and finish?

 

[r896neo]

I personally have not used the sika but know a few people who have and in their opinion it didn't set as hard and is more prone to algae growth.

i would advise a bigger joint to get enough jointing material in there but if you are going to try the 3mm joints you definately need a slurry apllied mixture as it is self compacting to a degree. You will never get any of the brush in products to flow into a joint that small and they certainly won't compact but rather stick to the sides and leave voids. (apart from basic kiln dried sand)

 

[indianjoe]

Many thanks for the tips - much appreciated.

Have taken your advice and gone for the GFTK product. had a quick chat with NCCstreetscape and they recommended the 840plus. Green joints have their place but my patio isn't it.

Know where I can get a good long handled squeegee?

If you can stop the temp dropping to freezing I'd be eternally grateful