Patio and pointing


28 Jul 2012
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West Midlands
United Kingdom

I hope someone can offer some advice.

I am having a patio done with Rutland Oakham paving kit which has 600x600 and 600x300 slabs.

The guy has used sand & screed and cement in a dry mix which has semi hardened but its not solid hard.

Now some of the slabs do move slightly and he has gone around and fixed with basically adding more of the mixture underneath and as I find more his fixing them.

My issue is with pointing now. I tested a few slabs with various building sand and cement ratio of 3:1 and sharp sand and cement with a ratio of 2:1 but both of these pointing has crumbled after couple of days.

I am thinking its because the slabs are not stuck to the base that they have a slight give and hence the pointing is not sticking. He wanted to use a wet mix for the pointing which I refused due to possible staining on the slabs etc hence my own tests.

So what are my options? Do I need a solid pointing or can I use a flexible pointing mix...the gaps range from approximately 5-10/12 mm. Or should I get the guy to re-do this with a full bed of mortar?

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Nothing wrong with laying on a dry sand and cement mix, but they need to be laid so there is no movement. Sounds to me like the problem is with the laying, not the method. They don't really stick to the dry mix, but that doesn't mean they should move when you walk on them. There is no point (!) doing the joints while they are still moving.

Paving expert has loads of info on how to do the laying and the pointing.
Thanks for the reply.

I think the issue is that the are differences in the slabs and some edges are higher than others so when you step on the edge the slab rocks slightly. Majority are fine just some that are not flat from underneath and stepping on the edge moves the slab.

Where I have done the pointing, the slabs don't move yet the pointing is very crumbly and comes away with a hard finger push after couple of days.

Is this because the sand cement was not mixed properly for the pointing? I have used 3:1 building sand and cement. 2:1 sharp sand and cement semi dry mix and in both cases it set hard by the second day but by the third day it came away and crumbled under slight push.

Am I doing something wrong?
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either the frost has got it or if you've had no frosts then maybe it wasn't wet enough.

Wrathkeg is right about the movement, the flags should not move at all and if they do the pointing will not last.

Personally I lay wet cast flags like yours individually rather than on a screed bed as the riven nature makes them slightly different thicknesses.

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