Levelling sub base

[Gra250]

Hi all. I'm new to the site and am looking for a bit of help. I am redoing my patio probably with sandstone flags. Whilst digging out most of the area is well below finished paving level but one area looks like uneven tarmac which was probably dumped by the builders. It is solid and not likely to move in my opinion. However it tops out at approximately 80 mm from the bottom of the flags. Given that there will be a mortar base of around 30 mm I expect this is to small a gap to bring up with mot due to the stone size. Please tell me is my best option to use a finer substrate like scalpings to level off or perhaps screed it with concrete? I don't really want to dig it out if I don't have to. Cheers in advance for any help. Gra

[rab1]

Keep your sub base consistent, its the part that matters.

[Gra250]

Thanks for the reply. So what are you saying? I should knock out the solid base and then backfill with a consistent 150mm plus of mot? Cheers.

[Tony McC]

Going off what you describe, you will probably be OK burying this 'base' within the DTp 1 sub-base.

[Gra250]

Thanks for the reply. So I should be ok even with about 50 mm of wacked down stone on top of the asphalt? The high spot is only about 1.5 SQM then it drops away. I do have some scalpings coming would these be best used in this are because of the finer aggregate? Thanks.

[Tony McC]

It's less than ideal but not the end of the world.

Scalpings. There's a not-very-helpful non-specific term. One man's scalpings is another man's skipfill.

I'd stick with the Type 1 - at least you know what it is!

[Gra250]

Thanks for the helpful reply Tony. I have been looking at the levels and can bring the patio up a bit still staying two bricks below dpc so should be able to get about 100 of stone on top of the asphalt so should be fine. When referring to scalpings I meant what would probably be type 2 which is about 20mm to dust I think. I thought this might compact better?

Another question I have a little off topic if you could help is. The patio is raised from the garden and L shaped. I have built a brick wall to retain the stone. Allowing for fall away from the house and the brickwork being level am I better cutting down bricks on the top course so that at the top of the fall line I don't end up with 50mm of mortar pointing on the side aspect. If this is the best way it is fine as I will be bringing the brickwork up another course to create the deeper bed anyway. Hope this makes sense it's difficult to describe in a post. Thanks again.

[Tony McC]

Apologies for delayed response - been in hozzy for a few days.

Cut down the bricks as required - no-one want to see 50mm of mortar!