The Brew Cabin

Exactly 4 years ago, a brickie "friend of a friend" layed me a patio of about 3 X 10m, on heavy clay, in wettish conditions. He dug out and compacted about 60mm of hardcore and then blinded with 35mm ofsharp sand, before laying the 40mm x 600mm x 600mm flags on mortar spots, without using a line or spirit level ! Suffice to say that within a year, all the pointing was breaking up, about 30% of thee flags were rocking, and the patio resembled a cross between a graveyard and an earthquake zone ! I ended up relaying all the "rockers", and re-pointing the lot. I can only presume that the combination of wet weather and spot laying resulted in the rocking flags, but i'm not sure why the pointing fell out.
Anyway, i'm shortly having a conservatory built, which will reduce the patio to about 3 x 5.5m, so i thought i might re-lay the patio myself, with random, riven buff flags.
Here's the plan !
If i can get the old flags up and remove the blinding layer without damaging the sub base too much, i hope to relevel the sub base with a vibrator plate, screed a 10:1 40mm bedding layer, lay the flags, and then dry point 4:1.
1)Will dry pointing be suitable, as it seems a lot quicker than the wet re-pointing that i have had to do.
2)Once the 10:1 bedding is mixed and is down on the sub base, how long will i have to lay the flags before it starts to " go off " and is no longer workable (probably depends on weather conditions i guess)
3)Would you advise screeding across the whole depth of patio ( 3metres ) by 1.5 metres or so across the width, flagging, and then repeating, or perhaps using another technique ?
4)Is it advisable to dry point as i go along, so the bedding doesn't go off before i get to point, as i don't anticipate being able to finish the whole patio, and then point it within the same day
5)The patio unavoidably slopes towards the house, so i already have a gutter channel layed between the patio and house. Will dry pointing be waterproof enough to withstand the water moving across the surface to the drain, or will some of the water seep down through the pointing and end up causing more problems with rocking flags?

Apologies for all the questions, but i want to do the job properly, and once only !
You're comments and advice would be greatly appreciated ! !

Finally, may i congratulate you on just about the most informative, relevant, and professional website i have visited for a long time. You are a credit to your trade.

Mark.

Brickies! Pah! ;)

Will dry pointing be suitable?

Yes, if done on a dry day. Don't expect it to last for ever, though. You get a better lifespan is you have buttered joints that are dry-pointed within an hour of laying.

Working time with 10:1 semi-dry bedding?

Around 4 hours. After that, you can reinvigorate it by adding a spadeful or three of fresh cement.

Screeding?

Yes - screed across the shortest dimension, remembering to allow 6mm or so for compaction. With less than 5m² to lay, you should be able top cover the ground before lunch time. :)

Point as I go?

You can do, but with such a small area, you could leave it until you've all the full flags laid, then go over it again when you've done any cutting-in.

Is dry pointing waterproof?

Not 100% but it will be satisfactory for what you want. Like the sand jointing used with block paving, dry-pointed joints develop a crust of crud that forms a pretty damned effective flexible waterproof seal after a few weeks.
If you want 100% waterproofing from day 1, then consider wet-grouting.

Good luck - let us know how you get on. :)

Tony,
Thanks for the info, i forgot to ask......
1) Are flags laid on a COMPLETELY dry 10:1 bedding mix
2) As i have nearly 16metres sq. to lay, not 5m sq. surely i must dry point as i go, as i'll never finish laying that lot in 2 days, let alone 1/2 a day ! ! !
3) As it will be difficult to remove all the existing blinding/bedding sand, would it be a good idea just to scatter some cement and rake that in before compacting it, and then laying my 40mm 10:1 bedding ?
4) Do i actually compact the 40mm 10:1 bedding layer and then add 5 - 8mm loose for compaction by the flag, or do i compact enough 10:1 to finish up 40mm thick after the vibrator plate, and then add the 5 - 8mm flag compaction layer ?
5) If i decide to "wet point", is it better to point to a flush level, or a few mm lower than the flag surface, as i've seen both methods with the riven flags i intend to use, but the flush pointing on my current crappy patio is all cracked and hasn't adhered totally to the flag, as if it has either shrunk, or frost/water has got under the edge of the flush pointing ?

Thanks again for your help already,

Mark.

(Edited by manic1 at 11:16 pm on Dec. 17, 2002)

Taking your points one at a time...

1 - it's not completely dry: it relies on the inherent moisture of the sand, so we call it a semi-dry mix. There is no water added during the mixing process.

2 - 16m² is still only 80-odd 450x450 flags, so if you can lay 10 an hour, you'll do it in a day. Dry point as you go, if you prefer. It won't do any harm.
Just to make you feel really inadeqaute, a professional flagger would expect to lay 16² in less than 3 hours. :)

3 - I'm not sure I follow. It's best to clear the entire site before starting to lay. YOu need to in order to get the plate compactor in to consolidate the sub-base.You can put out the bedding as you need it, stirring/raking cement into the sand as you require, if that's how you prefer to work.

4 - lay 50-60mm of bedding; compact lightly, screed off to 6mm or so high, and then lay flags. Only trial and error will determine exactly how high to levae the screed to allow for consolidation, but, with a 40mm bed, 6-8mm will be about right.

5 - point to slightly below the surface. Bucket handle pointing is best; that's the rounded, concave finish that's easiest achieved with a pointing bar or a short length of copper pipe.