Pointing on a new patio....

[danmun]

About 3 months ago we got a new patio laid by a builder at quite a hefty cost due to the size of space, about 60 square metres. We used sandstone slabs, 4 different sizes. All looked lovely when finished.

At the time I admit I was puzzled with the pointing, it was a dry sand/cement mix and not the older way of wet cement pointing. I was assured this was the "new" way to do this and it would set in time to form a hardish, although not solid, pointing.

We live in Kent and in the past 6 weeks have received a lot of snow as has much of the UK - anyway, I digress, but today I went out on the patio and I can feel movement in some slabs, only a little bit, but certainly movement. Also the slabs around the edge have started to come up and a lot of the pointing is now soft to touch and can be brushed out using only my finger.

My question is, is this method of Sand/cement dry mix the best way to point this type of patio? I want to talk to the builder to get him back to do it as not happy but wants some thoughts on alternative pointing methods.

Also, the slabs around the edge are not flush with the walls, apparantly you no have to leave a 2 inch gap for expansion - is this true?

Thanks for reading this essay and look forward to your thoughts and comments.

Dan

 

[Chukka63]

get the builder back.the pointing needs to be moist and compressed into the joints.never heard of a 2" expansion gap.the edge slabs really need some haunching against them unless you have grass etc to help hold them in place.

 

[Thermo]

Indian sandstone will not expandand contract to any extent. Did he perhaps leave a 2" gap because he laid it out wrong or didnt want to cut them? Got any photos?

as for the dry brushed in pointing, absolute pony. Its the new way to do it quick and cheap to get your money and then get out of there. As chukka says is the only way to do it.

i wouldnt be sure i wanted him back.

 

[WabbitPoo]

If the slabs are loose, it could also be the fact that he was hoping the pointing (such as it was) would hold the slabs rigily in place. This indicatres he laid them on a sand bed. Wrong!!!! They should be laid on a wet mortar bed.

As for the 2" gap, it could be that the pattern and slab sizes would not fit properly in the space, in which case there should be an even gap all the way around (if he wasnt going to cut slabs to fit) and this is best filled with gravel for decoration. Slabs dont expand much.

 

[danmun]

Spoke to builder today. He said reason for pointing and some movement in slabs around the edge was the hard frost we have had. He is coming back to fix the errors.

The gap around the edge is because of a rule saying you can't fix slabs right up the house???

 

[Thermo]

ask him to specify that rule. if there is an issue with the proximity to the damp proof course, then fine, although a gap of 4" should be left and backfilled with a free draining material such as pea shingle.

 

[danmun]

Thanks Thermo - I think that is exactly the answer, it's something to do with the damp coursing and he hasn't concreted the gap, it's been filled with slate chippings...does that sound above board?

 

[Thermo]

sounds ok, we normally leave a 4" gap, but that should be ok.

 

[WabbitPoo]

Spoke to builder today. He said reason for pointing and some movement in slabs around the edge was the hard frost we have had. He is coming back to fix the errors.

The gap around the edge is because of a rule saying you can't fix slabs right up the house???

First he says its an expansion gap (!) now this.....? Guy's a cowboy.

 

[Thermo]

love to see some photos of it out of curiosity

 

[ashymoko]

Sounds to me like the bloke knew how to do it but just couldnt do the practical side very well.
dry bedding is the best way to lay slabs the reason the slabs are moving and the edges are crumbling is purely dow to lack of cement in the mix, if the slabs are laid on a screed bed then its best to not give it any heavy traffic for the first couple of days especially the edges. 2" is the correct gap to leave up against the house below dpm, if its above it could do with bein a bit more and some dpm put horizontally across the brickwork before filling with a choice of easy draining material.
The grouting should be done with the same drymix as the slabs have been layed on, lightly sprayed, then left to set overnight.

 

[Thermo]

well you wont be laying slabs for me using that method, thats for sure

 

[danmun]

I'll try and stick some pics up Thermo.

Generally I think the fella is ok, he was a recommendation from a close friend, he's known him for over 15 years, so don't think he is any bother, think the pointing was the issue mainly, I just thought he would have used a wet mix rather than a dry sand/cement mix.

 

[ashymoko]

well you wont be laying slabs for me using that method, thats for sure

Lol, well its a good job im recognized by brett paving as a recommended builder, thats why im in their leaflet and thats why i wont be needing to lay any slabs for you!!
As i like to do the job properly!!

Danmun the reason he didnt wet point them up is because it would have looked hideous, especially on sandstone slabs. if drymix is applied as i suggested and mixed with enough cement it will dry hard and solid and wont crack. Leaving a much better natural finish than a wet pointing attempt.

Ask any true landscaper and he'll tell you the same. As will all of the top slab suppliers such as brett, marshall, etc.

 

[Thermo]

well agree to differ, personally i prefer a wet bed to lay them as there is no movement, and i prefer a slightly damp pointing mix, certainly not brushing it in. If its done properly then there is no staining. Ill carry on laying the way i do, that way i dont get any complaints from customers, who also employ me as a true landscaper.

how exactly do you lay indian sandstone on a screeded bed when all the slabs are off differing thickness anyway?

sorry i disagree with you about a 2" margin as well, since none of our local bco will accept anything less.