Patio - level or sloping?

[Bill's son]

a

Thank you

Bill's son.

[surreyhillslandscapes.com]

Firstly you need to at least start with something else than building sand for base...

[Bill's son]

So assuming I get rid of the builder's sand base... by mixing it with cement, would thi sbe half suitable?

I really have no other option but this right now.

[Rich H]

All the detailed answers are on the main site.

In short:

1. Use a sharp/coarse/grit sand & cement mix, semi-dry and individually bed each slab.
2. You definitely need a fall (slope) or you will have (a) puddling of water and (b) green algae and moss all over it within months.

[Bill's son]

Thanks Rich H.

Someone told me that if I didn't use a bed of mortar that the water would drain into the joints.

I have read the main site, and amzaingly comprehensive it is, but... I still don't understand how to compact the base while getting it on a slope???

If you use a compactor, does it not effectively level the ground?

Or, cruically perhaps, is the fall put in when laying each slab?

And if so, is this done by careful use of the spirit level? It seems to me that using a series of wooden pegs is impractical if you have a compactor running all over it.

Many thanks

Bill's son.

[Tony McC]

If you have an uncompacted laying course laid to a fall, then compacting it will maintain that fall. Compaction does not "level out": it compacts. So, if one end is, say, 50mm higher than t'other before compaction, it should still be 50mm higher after compaction. If it's not, there's summat seriously wrong with the sub-layers!

So: you excavate the sub-grade to create a fall. If you;re using a sub-base, then you construct that with a fall and compact it. Next, your laying course, again laid to a fall, and finally, the flags themselves, all laid to a fall, using a taut string line to guide line and level, and not a wooden peg to be seen.

Oh: and wazz that bloody building sand in the skip!

[Bill's son]

Ok, I hear you, Tony, just one thing... is the building sand beyond help?

I mean, can't I just mix in some cement to harden it up? Mix in cement, make sure it's got fall, and whack it?

Bill's son.

[Tony McC]

I'd be happier to see it trundling off down the road on its way to landfill, but, to be honest, if you mix it with cement at roughly 4:1, you could use it as bedding....but don't come crying to me if you end up with extra helpings of efflorescence and/or picture framing.

[Rich H]

After you've dug out, you can use pegs to set the level of the sub-base. If you've got a 4' or 6' level, place the pegs within that distance from one another. Most paving will be level in one dimension and falling in the other. As a guide, many people just align the edge of the bubble with the line on the glass. I like a greater fall with such riven slabs, but you'll have to work with the land as you have it.

Set the pegs at the finished paving height less the thickness of the slabs and the bedding course. With most IS, that's going to be about 6-8cm. Lay the sub-base just proud (3-5mm) of the pegs and then compact it, taking care not to compact the pegs as well. Once this is done lay the 'level row' of slabs first to set a datum for the rest. You can now lay the slabs to the fall using a string line as a guide for each row of slabs, which will save you forever messing about with the level.

[Bill's son]

I took delivery of the stone today - bloody great things.

It's begining to dawn on me why they are not laid on mortar - which was my original plan (remember, I have only ever before laid little cheap concrete slabs with four or five dobs of morter underneath!).

I also mixed up the builders sand with five bags of cement and laid this back down within 50mm of the top of the pegs that I set in, going from one side to another and creating a fall by putting the bubble just to one side of the line on the spirit level.

I tried to compact the lot but it was so dry the machine just dug in and made a mess of my level. So I dampened the site and tried again but it wasn't much better - so I tamped it down with a block of wood, making sure that there was 50mm of space below the top of the peg.

Next step is to lay the bedding proper - i have coarse sand for this, and put the flags on.

The flags vary in size. Some are massive and blooody heavy, some less so. They vary in thickness too from 25mm to 40mm.

Any more observations please?

Bill's son.

[Rich H]

Now's the time to read the main site under 'individual bedding'.

http://www.pavingexpert.com/layflag1.htm#indhow

Only the 900 x 600 ones are proper heavy and it's better if you have two people to lay those if you're not used to them.

You'll find opinions vary but for these slabs I add the following to the mixer: half to 2/3 bucket of water, six shovels sharp, three of cement, six of sharp again (for small mixers use less in proportion!)

Shovel the mix out of the barrow onto the sub base where you want the slab plus a bit of an overlap, feather it with a spade or trowel and lay your slab where it should be. Consolidate it with a maul or mallet, checking height and level before you move on. You might want to butter the edges a bit before laying the next slab to cut down your pointing time, too.

[Bill's son]

Ok, we'll have a bash at this tomorrow (Good Friday).

I have a big bag of grit sand on the drive and some cement ready too.

Thanks so far.

Bill's son.

[seanandruby]

using the brickwork as your starting point with your levels. measure the width plus 200 ml or so each side. come off square to the wall and pull a line. bang in a pin and tie you line to it. now using a spirit level adjust the line so that it is level. now measure down (50/ 60 ml or whatever your fall will be) from the line and mark it and tape it, do the same with the other side and re-tie the line to that you now have your fall using the lines as a reference. to get your cross fall, or level use another string line to go from one side to t'other. it sounds like you are using pegs for every row....not necessary and time consuming. re-building sand it is a no no. knock up enough mix to get you going , then a bit more as you get confidence. don't be scared as it can seem daunting.

[surreyhillslandscapes.com]

The lines here are set at paving height with a fall away from the house, each slab is layed on a ring bed of mortar with a small void underneath the slab so the mortar has somewhere to go when the slab is knocked down, when your knocking it down use a long straight edge to check you slab against the height of your lines and you should have no worries, hope this helps..

[Bill's son]

The bedding mix - should it be mixed wet? ie, 10:1 coarse sand:cement with water, or left dry? (or damp from the sand perhaps?)