Advice for base please

[Neilpet]

I am planning to do a patio in block pavers. I have started to dig out the area and have found it is clay and is really hard going t dig it out. How deep does the hardcore need to be considering there will be no heavy traffic on it ( except the misses lol!).

Fantastic site by the way.

[84-1093879891]

As it says in the Block Paving section, the sub-base should be at least 100mm thick. You could get away with 75mm if you have rock-solid clay (a high CBR) but anything less is a false economy and does not provide a competent sub-base.

[Neilpet]

After much digging the past two nights, I have in places dug too deep due to the clay coming up in big clumps. Is this ok to have deeper hardcore in plces than others ie up to 75mm more. I presume the more the better?

[84-1093879891]

More is better only up to a certain point. If you find you're putting in more than 150mm of sub-base, then do it in separate layers. Backfill the low spots with sun-base material first, then compact them, before topping-up over the full area to the required level, and compacting again.

It's great fun all this paving lark, innit? ;)

[Neilpet]

I never realised it would be so much hard work doing the preparation, especially as my day job is behind a desk! Still I keep telling myself it will be worth it in the end.

Thanks for your advice ,I dare say I will post again.

[84-1093879891]

You get a free six-pack stomach with every driveway (or a Party Seven, in some cases) ;)

When we do hand-dig work, we expect each operative to excavate and load into a skip at least 3 cubic metres per day. A good gang of 3 men will easily excavate and load 3 skips per day, with roughly 4.5 m3 per skip. On a soft dig, such as sandy loam or cow-belly clay, we can double that.

Maybe it's all that digging that made me the man I am today - a knackered spine and a dodgy ticker! ;)

[Neilpet]

Tony

Another thought whilst I am still digigng out!! I intend to lay a patio of the Plaspave Sienna blocks and border them with charcola pavers. I've seen a design that I'd like to copy( in the Plaspave book but in Rococo) but on the lawn edge the design uses the small charcoal kerb stones with the charcoal pavers inside them to continue that border round. Presumably though if I used the kerbs along the grass edge and that was the way the patio slopes, ie away from the house the water wouldn't be able to drain away? Is there a solution I could adopt or should I just use normal pavers all the way around.

Thanks again

Neil

PS No 6 pack yet, just the barrel I had before!

[84-1093879891]

You're concerned that the upstand on the kerbs will dam in any surface water, is that right?

Well, the pavement should slope so that the surface water is directed to a disposal point of one form or another, be it a gully, a linear drain or the public highway at the threshhold. So, the water runs across the paving, meets the kerb and then where does it go? Were you planning on draining onto the lawn? If so, can your lawn cope? How big is the area? What's the ground like in your garden?

It's not insurmountable, but if you can explain the falls and the drainage provisions, I'll be able to offer some solution, I'm sure. :)

[Neilpet]

Yes I was planning to drain onto the lawn. The patio area is about 6mtrs x 4 mtrs. There was an paved patio there before that drained onto the lawn without any problems. I was planning a fall of about 1:60 or 1:70 away from the house.

(This is a back garden and the patio is between the house and the lawn.)

[84-1093879891]

Right then - every 5th kerb, leave the joint open so that you have a 10-15mm gap. Fill the back of that gap with loose gravel or grit and that should allow the water to drain away.

[Neilpet]

That was pleasantly simple. I thought you were going to say that I would have to run a drain, constructed from hand made clay pipe laid 6ft underground to reach the River Severn just north of Bewdley!!

Thanks for your help again, I'm sure I'll be back when I either think of more problems or actually start work.

[Neilpet]

I have finally excavated the area for paving and am now ready to put the edging/kerb stones in place. I am planning to bed them on 100mm of concrete to bring them up to the finished level of the paving but do I need to dig a small trench to put the concrete in and if so how deep should it be.

Thanks again for a great site

[84-1093879891]

Depends on the kerb you're using, Neil. In mathematical parlance it is....

[Height of kerb] - [Amount of Upstand] + [Depth of Bedding]

.... below paving level.

So, if you were using, say, a 200mm high Boot Kerb, with 125mm of upstand, then the sum would be...

200 - 125 + 100 = 175, ie, you'd need to dig a trench 175mm deep measured against the paving surface level.

Does that help?

[Neilpet]

Not sure I'm quite with that, perhaps I didn't explain too well . I've excavated the area to a depth of 200mm below my fpl. I'm using a 200mm high kerb the top of which will be 100mm above my fpl (is that 100mm upstand). I haven't yet put in any hardcore so tonight i've tried to bed these kerbs on 100mm of concrete but because of the weight of the kerbs the front edge keeps sinking so i've thrown all my toys out of the pram and given up in a rage. I'm thinking now of putting in my hardcore and then just bedding them on a thinner layer when that's done, unless you can advise anything else?? Please help before I lose my sanity and the wife leaves me!

[84-1093879891]

The front edge of the kerb units is settling? Is that what you mean? If so, the only known cause for this phenomenoin is overly sloppy concrete.

Use a semi-dry mix; concrete with just enough water to make it damp. Not wet, not moist, just vaguely damp, so it just about clumps together when squeezed into a ball. Then, when you bed a kerb, it stays bedded, and doesn't 'float' or 'settle' when you come to lay the adjacent unit.

You could blind the bottom of the trench with sub-base material, but aim to be laying on between 75-100mm of concrete, if this is a retaining edge.