Ground levels and damp

[Timw]

I know that every authority on damp will advise reducing external ground levels to below those of the the internal floors. Sensible enough, but what is to be done when you simply can't?

Our Norfolk cottage is bounded on one side by a public road and on another by a communal concrete path. In both cases the external levels are perhaps as much as a foot above our internal floor levels and there is rising damp in the walls. It would not be practicable to lower the road or the path.

The architect involved in the renovation wants to put in a chemical dpc, but that would obviously have to be injected into the walls above the internal floor level! I'm not convinced that that is the answer.

Does anyone have any ideas?

Tim

 

[Gervase]

A chemical DPC is unlikely to work. Would it be an option to dig a narrow trench downwards to below floor level, line the wall side with an impermeable membrane and then backfill? You'd probably have to get the OK from the council's highways people, but they may well permit this if you undertake to make good afterwards.

 

[Penners]

I'm astonished that the architect should have suggested this.

OK - it might stop damp wicking up the wall above the dpc, but it certainly wouldn't have any effect on damp penetration below the dpc - which is presumably the area that you're mainly concerned about.

 

[Nemesis]

What sort of construction are the walls?

 

[SGray]

are you sure you have got the right architect for the job?

 

[Nigel]

Sounds like a french drain would be the ideal fix. Dig a trench, lay the drain, damp proof membrane against the wall and then fill with stones. So, as long as you can get approval for the stone finish that should address the issue.

We had one dug at our house and it seems to have done the trick.

Cheers


Nigel

 

[PC]

I fear that lowering of the ground on either side is a non-starter if backing onto public highway, paths etc. French drainage may also not be permitted you would have to discuss with council / highways.

The introduction of a chemical DPC (as recommended by your Architect) will do what exactly?

How do you know that the damp on the internal wall is rising damp and not penetrating, if you've got high external ground levels?

In the absense of lowering the ground levels you may have to consider vertical water proofing the wall...... if its that bad!

PC

 

[Timw]

Thanks for all your suggestions!

Would it be an option to dig a narrow trench downwards to below floor level, line the wall side with an impermeable membrane and then backfill?

That would certainly be possible, but I've read in the SPAB literature that impermeable membranes applied to brickwork "...tend to be temporary and break down." I guess that put me off but perhaps others here have had success with this approach??

What sort of construction are the walls?

Norfolk red bricks

Sounds like a french drain would be the ideal fix.

The foundations are almost certainly very shallow. The structural engineer has forbidden this!

How do you know that the damp on the internal wall is rising damp and not penetrating,

I may be using incorrect terminology. You're right, the water is probably penetrating, but once in the wall it is certainly rising.

Dig a trench, lay the drain, damp proof membrane against the wall

Again, I had rather dismissed this approach because of SPAB's assertian that such membranes are 'temporary' in nature.

 

[Nemesis]

I wonder though if SPAB means a cementy type applied?

Give 'em a ring.

 

[Timw]

No, they were referring to the bitumastic stuff.

 

[Gervase]

I was thinking more of Vandex or Newton 500, which are pretty tough. They won't be on SPAB's approved list, but with such limited access to the outside, desperate measures may be needed (though not as desperate as a useless chemical DPC!)

 

[SGray]

Timw - do a search on this forum for the thread entitled "the best option for damp lower ground floor".

 

[Nemesis]

I agree re the bitumastic stuff - the stuff you paint on - don't go there!
But there are certainly other options.

 

[Timw]

Again, thank you all for your contributions.
Tim