Can I replace soil with gravel, from around exterior skin of wall?

[Safety First]

Concrete (driveway) was 4 inches over DPC. This now gone. Dug down about 9" more. Natural stone under last brick course. Filling trench back in, albeit below DPC, can I fill in with gravel instead of soil?

Thinking that the Soil will hold water, where gravel will drain and let (some) air circulate???

Uncovered stone course below bricks is flush/plumb with bricks so not actually footings (they are deeper still, I hope) so can I use gravel to hold it all in place? ...With a membrane to keep the gravel clear of soil etc.

Is there some blend of chippings with cement that will lock up/set, but still let air circulate and drain well?

cheers all

 

[stuart45]

Is there some blend of chippings with cement that will lock up/set, but still let air circulate and drain well?

cheers all

Do you mean No Fines Concrete, which is only about 5% sand.

 

[John D v2.0]

Do you mean No Fines Concrete, which is only about 5% sand.

This sounds great but doesn't it get silted up after a while and stop draining?

 

[Safety First]

That concrete looks pretty special. I was thinking more something like a sheet of terram? membrane with stone chippings poured in. I think I heard of something where cement is added to gravel? It makes no sense- thinking about it, that the cement would have anything to grip to, but the aim is that the chippings will compact and hold bottom of wall firm, drain (better than the soil that was there), and let more air through.

 

[stuart45]

This sounds great but doesn't it get silted up after a while and stop draining?

Good point. It may well do, but I don't have any practical experience of it as a driveway material.

 

[Safety First]

Good point. It may well do, but I don't have any practical experience of it as a driveway material.

Yes,.... as a driveway material I can imagine lots of stuff getting into its 'pores'....
Though, if you have dug down 9 inches below DPC and want to back fill with something better than the soaked soil, that will drain and hold firm the wall (I am paranoid that the wall is going to move without the soil there) then mixing up some of this 'no-fines' stuff would do? yes?

Should I under wrap it with permeable membrane?...

Thanks

 

[stuart45]

Should I under wrap it with permeable membrane?...

Thanks

Probably best to. It's done nowadays with French drains.

 

[stuart45]

You don't need as much cement with no fines, usually about 8/1.

 

[Blagard]

I looked at that Topmix solution. It can only be used in specific circumstances as the underlying sub bases need to get rid of the water to. I would question the ability to resist frost and the literature indicates that so long as there are voids the water/ice has space to expand into. I would think if it gets water logged it could breakup. Nice to see Careys on the video, they worked on my last job before retirement from the industry.

As for the OP's issue as already said permeable membrane with loose aggregate on top is fine. It is not intended as a proper french drain so any aggregate could be used but avoiding those with fine materials in them. So some of the decorative aggregates can be considered.

 

[Blagard]

This sounds great but doesn't it get silted up after a while and stop draining?

Quite so, you need to read the literature on it because it should not be used where that is likely. It even bans construction traffic from it after it is laid and I think we all know why that is!

Edit:
I am quite sure it has a lifespan as just dust slowly building up will eventually clog it. So it may only be suitable in some very special cases with the knowledge that say in 20 years it will no longer be effective without replacement. LOL no car washing allowed on that surface.

 

[Safety First]

As for the OP's issue as already said permeable membrane with loose aggregate on top is fine. It is not intended as a proper french drain so any aggregate could be used but avoiding those with fine materials in them.

Thanks for the input.
If I may persist.... Just to be clear about what you mean,.... do you mean chippings over perm membrane over the top of the no-fines concrete mix. I'm wondering if the removal of the soil down to 9" below DPC would warrant replacement with no fines conrete (to hold wall in place), or whether you'd say just weight of chippings would hold it solid.

Guess it's diff to say given you have not seen it...

Just fearing that the 1930's footings might be minimal... yonks ago someone told me I was in danger of the wall falling over if removing too much of the soil around the base.

Cheers again!

 

[stuart45]

The bit you shouldn't dig out is known as the Angle of Repose which is taken from the base of the foundation at an angle of 45 Degrees.
This transfers the loads to the ground, so the earth as the sides are not so important.

 

[Blagard]

Thanks for the input.
If I may persist.... Just to be clear about what you mean,.... do you mean chippings over perm membrane over the top of the no-fines concrete mix. I'm wondering if the removal of the soil down to 9" below DPC would warrant replacement with no fines conrete (to hold wall in place), or whether you'd say just weight of chippings would hold it solid.

Guess it's diff to say given you have not seen it...

Just fearing that the 1930's footings might be minimal... yonks ago someone told me I was in danger of the wall falling over if removing too much of the soil around the base.

Cheers again!

I meant just put membrane and chippings back. No concrete at all.

If you have other relevant information please advise. i.e. Is the house on a hillside, Did rainwater use to run across the concrete up to the house? If you have any concerns that the foundations are really shallow then just dig a trial pit (not a trench) to find out how far down thay are to the underside. The hole needs only be big enough so you can see! No huge hole required. If you have not found the underside at 500mm down just leave it!

 

[Doggit]

Within a few years, gravel will have filled up with silt, and would act the same as having earth there, so you want 1" stones in the trench. As long as the water will dain out of the bottom of the trench, then you'll be fine.

Unfortunately, paranoia relating to the wall caving in without the soil there, is not a recognised condition, so you'll have to deal with that one yourself, but trust us, the wall will still be standing in a 100 years.