laying base for block paving

[markyyyyyy]

Hi,

i have just built a curved front door step using some radial bricks. These have been laid on to a concrete foundation.

I have a bit of type 1 hardcore left, and a lot of gravel, so i have chucked a load of this in to act as a sub base. My only concern is that when i lay the sharp sand to which the block paving will lay on, that it will wash through into the gravel. is there anything i can do/buy that will fill in the gaps inbetween the gravel, so to make it compact, and firm base to lay the sharp sand on before paving?

Could i buy some ballast or building sand? Do i need to put a membrane down (if so, which type?) on top of the sub base, before laying the slabs with a 4:1 sharp sand and cement mix?

Many thanks

mark

 

[John D v2.0]

I'm not clear what the question/issue is, but you should have dug down to solid ground ie sub soil, put down the hardcore, whacked it, then concreted in the edges of the drive/step, then laid the inside of the step on screded sharp sand.
In my case I just made up the edges with concrete directly on the sub soil and then put the hardcore in the middle, but it's not the recommended way.
If you deviated from that it's fine as long as you have a solid base and the edges are restrained properly. No need for any fabric membrane

 

[markyyyyyy]

i just put a big rectangular base of concrete on to the compacted sub soil, and on here i laid the radial bricks directly on to the concrete base.
I am now left with a gap inbetween the bricks and the door, so i chucked loads of gravel and a small amount of type 1 hardcore in there....

This is what it looks like right now:

p.s. i need to add more gravel in the morning to bring the level up a bit

So what do you suggest i do? There will be some larger gaps in the sub base as gravel is in there with not much dust. Should i just get a bag of sharp sand and chuck it in (to fill some gaps) before adding more sharp sand to make up the layer of sand to which the paving blocks will be laid on?

cheers

 

[John D v2.0]

Ah yes it's only a step so doesn't need to be strong, just need to avoid the base being lost/washed out. It'll be hard to screed stones nice and flat so I'd definitely put something on to of the stones.

 

[markyyyyyy]

Ah yes it's only a step so doesn't need to be strong, just need to avoid the base being lost/washed out. It'll be hard to screed stones nice and flat so I'd definitely put something on to of the stones.

so, do i put some sharp sand on top of the gravel, then a polythene sheet (with some fine holes in??) and then the sharp sand base for the paving?

is that what you suggest?

cheers

 

[John D v2.0]

I'm not suggesting a sheet at all, if it was me I'd just mix in just enough sand to get rid of all the voids then screed a layer on top for bedding.

 

[markyyyyyy]

I'm not suggesting a sheet at all, if it was me I'd just mix in just enough sand to get rid of all the voids then screed a layer on top for bedding.

okay cheers - so it would'nt wash away into the gravel with rain water?

i was planning on doing a wet mix with 4 parts sharp sand with 1 part cement, so maybe this will firm it up a bit?

 

[John D v2.0]

The idea is to have no voids for the sand to wash into.
Concrete base then sand on top would work for strength but be overkill for a step and wouldn't drain at all, not sure of that would be a problem but probably not.

 

[r896neo]

Your concern is valid. Best way around it is to lay the step on a mix of screed sand and cement. About 8:1 will do, float it smooth and gentle tap the blocks down into it with a plank to compact them to your final levels.