Pointing chamfered slabs - Using polymerics with chamfered slabs

[onceinawhile]

This is a brilliant site, but after checking past posts I still feel need of some advice about pointing my recently relaid patio – in a nutshell, what pointing to use with chamfered 38mm slabs which butt at the bottom and leave 7-10mm joint at the top?

I just looked at eg the Aspects Easyjoint video and it states very clearly that there should be at least a 3mm gap between the bottom of the stones, if they are chamfered……….. I have no real gap.

Fuller story is that we have 15 sq metres of 450 x 450 ‘riven’ concrete slabs that I first relaid 25 years ago when we moved into the house. I didn’t mortar the joints and they had become uneven – ants and weeds at work – so I recently relaid them again. We did look at getting a new patio but my wife thought about the carbon footprint and I thought about the cost!

The substrate is just well-packed clay soil with an inch or so of sharp sand. I don’t have use of my legs, so didn’t feel up to digging it out and putting in hardcore. But I want to stop the ants and weeds this time and had thought to use a polymeric like Romex or Rompox.

(I should say that thanks largely to info on this site, I have put in some very nice Marshall’s 50 mm sandstone steps down to the patio – but these on a 6 inch concrete base…… and they also await pointing.)

[Carberry]

Sounds like your slabs are upside down.

[onceinawhile]

I'm not quite that stupid, Carberry!

They slabs do only have the riven effect on the top. These slabs are wider at the bottom than the top - butt them together at the bottom and you have an avge 8/9 mm gap to point. I wouldn't want a gap wider than that, but the resin-based fillers seem to specify a continuous gap to the substrate, ie slabs not butted at any point. I just wondered if anyone had experience of using a resinous mortar with chamfered slabs, and whether the mortar is likely to stay in place.

[Carberry]

Had to check, you would be surprised at how many supposedly qualified people lay upside down slabs. It isn't ideal but the pointing will hold.

[onceinawhile]

Thanks for your advice. I will probably get the gtfk Easy Joint. Not cheap, but I saved by not buying slabs. If anything goes wrong, I can pass it on!

[DNgroundworks]

May i ask, how did you manage to lay flags if you dont have the use of your legs?

[onceinawhile]

Hi DNgroundworks. I just have to get out of the wheelchair and work on my backside - sunny weather only! That's one reason why I discarded the 600x600x50mm slabs - over 40 kg each, and too heavy. But groundwork is not my problem - ceilings are the challenge.

[DNgroundworks]

Wow i bet that was serious hard work! fair play. Ive used the gftk 800 slurry, fantastic stuff.

[onceinawhile]

Not having used any of these products, I was nervous about cleaning off slurry, but is that what you would advise?? Had thought to use the 840plus dry. (84 quid inc for 25kg from PavingExpert..... which would be about enough.)

[GB_Groundworks]

carberry they are concrete not indian stone, ive never seen anyone lay a concrete flag the wrong way up

[haggistini]

Hi DNgroundworks. I just have to get out of the wheelchair and work on my backside - sunny weather only! That's one reason why I discarded the 600x600x50mm slabs - over 40 kg each, and too heavy. But groundwork is not my problem - ceilings are the challenge.

FairPlay to you sir ! I shall be informing a few people tomorrow of your ability to lay slabs in your position......amazing!
As for the GTFK call me tomorrow and I'll talk you through how I would go about using it !

[jonnyboyentire]

I would use the 800 personally. Strong as the proverbial. Knocking it up could be a problem though for you - we use our mixer.

[onceinawhile]

Thanks guys.

Jonnyboy, I have a drill paddle but would prefer dry mix because of the speed of working required with the wet mix. Thge alternative to a dry mix for me would be to buy a gun and mortar the joints slowly.