Author Topic: Laying paving question  (Read 444 times)

caerau

  • SR x 3 - PBP fail but 1090 km - hey - not too bad
Laying paving question
« on: June 09, 2019, 01:06:24 pm »
Hi all, our back garden is partially slabbed with paving already, but we have an annoyingly large area of it that is sharp stone instead and this has always prevented us walking say barefoot in that area.  So we're thinking to replace the gravelly bit with standard 900x600 mm paving slabs.
Would just give us more room for manoeuvre in the garden allowing us to move our table away from the only area that is slabbed...



Now in my opinion, I reckon I can just shovel and dig out the top layer of gravel/aggregate that's on the surface and just lay the paving slabs on top and that would be just fine.


But... I read that you should dig out the area and set a good base with cement/sharp sand first.  But the gravel that's there already goes quite deep and has been compacted in already for lots of years.... so do you think I could get away with not bothering with laying a cement base?


I *can* always lift the slabs and lay a cement base afterwards if it really does go tits up...


What do our DIY gurus think? 


Cheers for your thoughts.
It's a reverse Elvis thing.

caerau

  • SR x 3 - PBP fail but 1090 km - hey - not too bad
Re: Laying paving question
« Reply #1 on: June 09, 2019, 01:20:34 pm »
Here's the area I'm talking about for more info...  also - when I'd explored downwards through the stones - I don't see an obvious cement/sand base under the paving slabs already there...

It's a reverse Elvis thing.

Blazer

  • One too many mornings and a thousand miles behind
Re: Laying paving question
« Reply #2 on: June 09, 2019, 02:35:36 pm »
I'll watch with interest for someone who knows what they are talking about but...

I'd understand the sand / cement layer makes it easier to get a level base to lay the slabs especially if you already have a weight bearing sub layer.  I guess it depends how big your current aggregate is as to whether it is 'easy' to lay slabs level directly on top.  If it is sufficiently small aggregate then I'd lay direct on top (see opening caveat).  What are you doing to prevent weeds creeping through?  Are you pointing the slabs or butting up?

I've usually gone with a dry sand/cement mix of around 40mm depth as it then pretty easy to level and lay each slab but I appreciate that is more cost and faff.

Pip pip

Carlosfandango

  • Yours fragrantly.
Re: Laying paving question
« Reply #3 on: June 09, 2019, 08:10:04 pm »
I've laid a few of this size concrete slabs in the past. They are extremely heavy and only just manageable by one person. The weight makes them difficult to lay, because they're difficult to manoeuvre and you may have to lift them to level. They will move any loose base as you move them into place. You'll have to cut them as well. I laid mine on dry mix. If you're not diligent levelling them they look pretty awful. I'd advise getting the smaller size, much easier to manage.

Get them delivered, you'll only manage 3 or 4 in a car, the suspension will be on the stops.

Have fun.

caerau

  • SR x 3 - PBP fail but 1090 km - hey - not too bad
Re: Laying paving question
« Reply #4 on: June 10, 2019, 11:50:44 am »
Cheers for the interesting points.  Yeah, without trying to be conceited I am quite a bit physically stronger than your average person (what makes me rather unideal for cycling has its benefits elsewhere, I have deadlifted 200 kg in the gym in the past and bench-pressed 150) - but I think you're right, they will indeed be very heavy nevertheless.  I have proper tools for the job, I've built up loads of DIY tools over the years but I'll need a stone cutting blade for the old circular saw for sure ,there is a drain in the way by our back door.
Looks like enough slabs is going to cost us about £400 anyway - so we're looking at seeing what our local slabbing firm will quote - there's a firm that's paved over half the neighbourhood's driveways recently with ads outside every house - I think they are cheap or it wouldn't have been quite so viral.
We'll see what they quote, but it's always more satisfying to do the job yourself I find.  No hurry either so I don't *have* to lay them all the same day.


I don't even possess a car so carrying them on my bike seemed a little unlikely anyway ;)
It's a reverse Elvis thing.

Re: Laying paving question
« Reply #5 on: June 10, 2019, 11:59:46 am »
.... with standard 900x600 mm paving slabs.
.

As carlosfandango says, those are real beasts to lay. You don't say how deep the current slab/gravel edge is - from the photo it doesn't look as if it would be deep enough to use those slabs which IIRC are around 50mm thick or more. If it is stable  and you have a few inches of gravel, then removing sufficient to allow a layer of sharp sand will likely be sufficient. You will need an 8in grinder with a diamond blade for best results, a 4in grinder isn't really going to cut it well enough.

caerau

  • SR x 3 - PBP fail but 1090 km - hey - not too bad
Re: Laying paving question
« Reply #6 on: June 10, 2019, 12:16:51 pm »
There's already a bunch of standard 900mm/600 mm slabs there, just only outside the French windows (where I took the photo from - you can see the edge of them in the photo). 


I've dug down next to the existing ones and there appears to be no base that I can determine - they have remained stable and flat for the 12 years we have lived there - which is what leads me to believe that the aggregate is deep enough already - certainly, the aggregate doesn't disappear to ground soil as I get below the current slabs - I suspect it's deep enough - there shit-tonnes of it below the raised beds and bottomless pot staircase at the back of that photo too - I think they used the aggregate liberally to foundation much of our rear garden area (and the front too as there are hundreds of bottomless pots going up the slope there too).


If I do go through with this - seeing as I forgot to mention - I would just weed any weeds ;). And we'd just butt the slabs up against one another as they are already (the ones already there).
It's a reverse Elvis thing.

fuzzy (retd.) AAGE

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Re: Laying paving question
« Reply #7 on: June 11, 2019, 09:33:48 am »
I have been doing a fair amount of DIY slab laying recently, of cheap B&Q 400 X 400 slabs so not as hefty as yours.

Previously I have dug out 4 inches below finish level, 2 inches of ballast sub base topped by sharp sand as the bedding medium. Just sand makes levelling easy BUT, hasn't held it's level or stabilitiy over time. I think this is more a case of lightweight slabs will move easier than big buggers.

My more recent activity has replaced the sharp sand with a mortar mix. A bit (lot) more tiring as I have been mixing the mortar by hand and a bit more involved at getting the level right. The slabs have been more stable however.#

Looking at your area, I reckon that you need to skim the top of the chippings down to at least a slab depth plus an inch (2 preferably) below the desired finish level, a thin layer of sharp sand on top of the remnaining stones which you need to compact in the provide your stable sub base then an inch or two of sharp sand as the medium to lay the slabs on.

I have no experience of cutting slabs so can't advise there.
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