The Brew Cabin

Tony,
We have apatio measuring about7m80x3m80 and it has old concrete flags laid years ago. My wife would like the small border/flower bed removing and additional flags laid. She has chosen Marshalls heritage and these need to be laid on the 10:1 mrtar mix. Can I lay the old flags on sans and only use the concrete for the new ones?
My wife would like the new ones placing randomly around the the patio.
Mozza

You can, if you wish, but to be quite honest, you'll find it a lot easier to lay them all, old and new, on the 10:1 semi-dry mix - it's a lot more forgiving of incomplete consolidation than is unbound sand, which is why I recommend it for DIYers.

Tony,
Thanks for the reply; can I ask a littlemore..
1) the patio is enclosed by two walls and the house wall.I'm going to slope away from the house and lead rainwater to the far wall and then knock the odd brick out and put pipes through. Is this okay?
2)How level does the ground need to be before I get to the serious bit of the job? I followed your advice the the brickweave drive but that was levelled to the Nth degree.
3)When I am laying the slabs-the old ones are 45mm thick and the new ones are 38mm. Can I put down an even thicknesss of the dry mix amd just tamp them down to level or do I need the mix to be thiccker for the 38s?
4)When I am staggering about with the flags I will be standing on the ones I've already laid.Will this push some of them down more and make them all uneven?
If so how do I fix it?
5)If I butter the edges as I lay will this reduce the time I have to before the mix goes off?

Regards,
Mozza

1 - Why not use a length of linear channel and then simply make one hole through the wall for drainage?

2 - the sub-grade needs to be roughly level, allowing for falls, but ±30mm is fine

3 - With only 7mm difference between new and old, I'd not worry about it at the prep stage but allow for a slightly thicker bed under the new flags. If you lay the old flags on, say, a30mm bed, then the new ones will take around 37mm - nowt in it, really! :)

4 - if you've used a semi-dry mix for the bedding, there shouldn't be a problem, but try to avoid standing on the edges of the flags. If you use a moist mix, more care is required, and it's best to lay a decking sheet (2400x1200mm sheet of 18mm ply) over the flags to help spread the loads as you work, moving the sheet up as you proceed.

With wet mix, it better not to work from the just-laid flags at all, and to find some way of working from the sub-grade/sub-base.

5 - Buttering has no effect on working time of the bedding, but does reduce the amount of time you need to spend pointing the joints.

Thanks again Tony,
There are two things that I find ball aching about this work viz humping the soil about and getting the levels right. The first one I can do but it expands the time for the job;the second one makes my head hurt-if I get the level right in one place I find it really difficult to get the fall right and even.I was afraid that if I put a long drainage channel in based on your 1 inch fall per metre I wpuld have to produce an 8inch grade for the 8 meters and the amount of soil I would have to move would be garganthian. I thought the best way would be to have smaller lengths sloping toward the drianage pipes (if that is making sense).
I'm still slightly concerned about moving my 13stones and a flag across the newly laid flags.I assume that I tamp down to level and not to the bottom of the available mortar voidage-which will be supportive when it has set but will still have some spare compressive capacity when laid.
I'm also having trouble with a ramdon pattern. I have to acccomodate the 50 2'x2' flags and I don't even know what DXF is let alone understand it. Can I download it from any where.

Regards,

Mozza

If you use a linear channel drain, it can be laid with very little fall - 1:100 is fine, and that will save you a lot of 'humping' compared to that required to have the paving laid to a fall of 1:40. Over your 8m length, you could get away with as little as 40-50mm of fall (1:200) as the channels will allow water to flow under hydrostatic pressure (water that falls into the channel "pushes" the water that's already in there towards the exit point).

If you're still fretting about walking on the flags, use the decking sheet idea - it really does work!

You can't make a random layout from just 600x600mm flags - you need at least 2 differently sized flags to make random layouts. You could opt to split some of the flags into 2 @ 300x600mm, which would then enable a very rudimentary random arrangement. However, you need to introduce at least 3 sizes to get anything that looks half-decent.