Patio groundwork

[Moojuice]

Hi Folks,

This question relates to a few categories but I'll post here to start. I'm a competent DIYer but haven't done anything like this before except for a loose paved shed base so apologies for stupid questions and wrong terminology!

The problem: My patio is to the rear of the house 13x3m. The house is on a downward slope so the patio is raised on a bank then has steps from the centre going down to the lawn. It is currently paved with horrible 20x20cm pebble dash effect slabs. The base (or lack of it) is concrete at the steps and a couple of the corners which are sound. The rest of the base is just rubble and earth so predictably it has sunk in places and is generally very uneven and rain pools in the low spots. The slabs on the earth are not mortared in any way. It's original to the house (40 years) so the uneven base is now very compacted and firm.

Plan A: Initially I thought of building shuttering around it, levelling with suitable aggregate, compacting and then filling with concrete (100mm deep) reinforced with steel mesh (possibly overkill but I don't want it to break up). This would then be a good firm base to lay exterior tiles on. Tiles would be easier to cut / lay especially on the steps.

Question 1: Is a slab of this size possible without breaking up due to expansion & contraction? If not I assume I need control joints every 3ish meters which is going to look really ugly due to the close tile spacing. I'm confused here because I've seen larger concrete slabs with no control joints that don't seem to have any cracks but everywhere I've read has said they are necessary.

Plan B: Level, aggregate & compact and then use mortar and chunky flagstones. The steps could be tiled in a different material which is not ideal.

Question 2: If a concrete slab of this size expands and contracts, why wouldn't the mortar? I assume it does but because the gaps between the stones are chunky it is less noticeable and would only need re pointing after the initial cracks?

In a nutshell, I need a solution that is not going to break up, is hard wearing but is also fairly easy to fit. Would either of the above work or is there another way of doing it?

Any suggestions appreciated.
Thanks,
Alex.

[lutonlagerlout]

I think you are over engineering it

have a look here

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

generally 100-150 of subbase and then 40-60mm of bedding is adequate for patios

most on here have used this technique for donkeys years with great results

expansion never seems to be a real issue with patios,why ?
I dont know

cheers LLL

[Moojuice]

Over engineering, over thinking it? Guilty on both counts, standard for me! Granted what you suggest is easier and would work (I've read the page already) but I'd like to do the steps and other tricky areas in the same surface which is easier in tiles. And I can't put tiles on subbase and bedding. So, my preference is the concrete slab but will it survive in one chunk or am I stuck with building a patio as you / the link suggest and doing the other bits separately?

Cheers.

[seanandruby]

The name is in the site ' paving expert', not tiling expert ???
Just use flags/slabs using the spec shown on the index, it's all tried and tested. A cut is a cut is a cut whatever it is on :;):

[r896neo]

If your doing it yourself i would pave it.

If your paying someone very good to do it then you could do the concrete and tiles approach.

Outdoor concrete is a very cruel mistress, especially when using a thin bedding such as tile cement. Your falls etc have to be spot on and your finishing done to a good standard without creating dishes/ bumps which is easy to do when floating etc.

Then throw in the general headaches of concrete outdoors such as weather, temperatures etc and its not an easy prospect for even a good diyer.

You'd certainly need one joint in the 13m length. perhaps 2 but i'm not a concrete expert.

[Moojuice]

Ok, fair points on the concrete. I've seen loads of 'how to' vids on youtube where huge concrete slabs are poured easily with no joints of any sort but you never see the result a day / week / year later. The above advice sounds more realistic. I'll go ahead with that advice and just rethink how to do the steps and other bits.

Thanks again for all the comments.

[GB_Groundworks]

Because the large pours have engineered solutions for contraction it's not just by chance

[Captain Concrete]

I do a fair bit of concrete for a very good patio man he uses screed rails every 4m mainly not for expansion but for screed rails to tamp of and to get the correct falls I will declare a conflict of interest as we sell the screed rails.

http://www.proformconcrete.co.uk/galleri....ed-park