Lowering Ground Level

[james19000]

ground levels

• james19000
• 6 Aug 2025
• 2

I’m lowering the ground level in front of a 1900 Victorian property to tackle damp. I’ve attached a cross-section illustration showing the situation clearly.

I have 3 questions:

QA: How wide should the ditch be? 150/200mm?
QB: How deep should the shingle be?
QC: How deep should I dig the original soil level?

• The presumed slate DPC is approx. 200mm below the internal floorboards.
• The original soil level sits about 150mm above the DPC.
• Below the DPC, there’s a projecting brick course, about 50mm lower, which will become fully exposed if I dig down to 150mm below the DPC as recommended in the damp report.

My concerns:

• If I go down the full 150mm below DPC, the projecting brick will be exposed — is that okay?
• These bricks may not be frost-resistant underneath — could this lead to long-term damage?
• Could it act like a ledge and trap or splash water back up the wall?

Three options I’m considering:

1. Dig down fully 150mm below DPC and somehow protect the projecting brick (e.g. gravel + vertical barrier).
2. Stop digging at the top of the projecting brick (i.e. 50mm below DPC) and add a shallow channel or slope away from wall.
3. Something else entirely? (e.g. combine surface drainage + ground lowering further away)

Has anyone tackled something similar or have experience with old walls and projecting bricks in damp remediation?

Appreciate any guidance before I commit — thank you!

 

[noseall]

ground levels

• james19000
• 6 Aug 2025
• 2

View attachment 389154
I’m lowering the ground level in front of a 1900 Victorian property to tackle damp. I’ve attached a cross-section illustration showing the situation clearly.

I have 3 questions:

QA: How wide should the ditch be? 150/200mm?
QB: How deep should the shingle be?
QC: How deep should I dig the original soil level?

• The presumed slate DPC is approx. 200mm below the internal floorboards.
• The original soil level sits about 150mm above the DPC.
• Below the DPC, there’s a projecting brick course, about 50mm lower, which will become fully exposed if I dig down to 150mm below the DPC as recommended in the damp report.

My concerns:

• If I go down the full 150mm below DPC, the projecting brick will be exposed — is that okay?
• These bricks may not be frost-resistant underneath — could this lead to long-term damage?
• Could it act like a ledge and trap or splash water back up the wall?

Three options I’m considering:

1. Dig down fully 150mm below DPC and somehow protect the projecting brick (e.g. gravel + vertical barrier).
2. Stop digging at the top of the projecting brick (i.e. 50mm below DPC) and add a shallow channel or slope away from wall.
3. Something else entirely? (e.g. combine surface drainage + ground lowering further away)

Has anyone tackled something similar or have experience with old walls and projecting bricks in damp remediation?

Appreciate any guidance before I commit — thank you!

DPC level presumed by whom? I can't imagine a builder putting a DPC there lol.

 

[james19000]

DPC level presumed by whom? I can't imagine a builder putting a DPC there lol.

Presumed by me oops
If you don’t mind reviewing the photos in the gallery, could you identify where the dpc is…
That would be a great help.

 

[Deluks]

Yes, that's the wrong place for a dpc, there's no evidence of one in the photos, it could be behind the band of render, which in itself could be bridging it.

 

[cdbe]

DPC would usually be two bricks below internal floor level, in line with the bottom of the air brick.

If it's your house and your doing it properly (it all looks a mess at the moment) you should remove all that old render, replace the cracked bricks and physically find and check any dpc. A "trough/french drain" would normally be 150mm x 150mm from dpc, but depends if the soil is sufficiently permeable - see how what you've already dug out behaves when it rains.

 

[Munroast]

outside ground level could have easily increased since 1900 - the slate DPC could easily have been buried
have you exposed slate at the level ?

 

[Ivor Windybottom]

If you do end up doing this I'd put something to retain the soil between the soil and gravel. Otherwise you'll just end up with muddy gravel, which will be no better.

A retaining wall or paving slabs on edge bedded in concrete. Or a path on concrete and/or compacted rock.

You will need some form of drainage for your gravel, otherwise you're creating a potential moat against the wall.

 

[noseall]

Presumed by me oops
If you don’t mind reviewing the photos in the gallery, could you identify where the dpc is…
That would be a great help.

You appear to have exposed the stepped foundations. Don't dig any lower or seek to drain the ground around your foundations. You are better off laying perimeter drains or hard paving, thus collecting the water and discharging it away from the house.

 

[Ivor Windybottom]

I believe it's OK to dig or drain to the level of the bottom of the foundations.

It's not OK to dig or drain below this level.

So OK to carry on digging, it's just how it was done in the old days to spread the load. Nowadays it's done by building a vertical wall on top of a wider lump of concrete. Either way it's OK to dig alongside it, not beneath it or alongside it below the depth of its base.