'Green' damp proofing

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'Green' damp proofing
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Barnie

Joined: 26 Jan 2007
Posts: 40
Location: SW/Wales

Posted: Sat Jan 27, 07 1:46 am Post subject:

300mm width is fine and 450 to 600mm below top of foundations at it's highest point, the trench needs to slop off all the way and idealy exit somewhere convenient, it can exit into a soakaway if necessary but best freeflowing out into a nearby drainage ditch, perforated pipe layed on the bottom of trench covered with drainage stone.

Differing ground conditions and underground spings can complicate things but generally the above will suffice.

Armchair

Joined: 14 Jan 2007
Posts: 205
Location: Winchester

Posted: Sat Jan 27, 07 11:15 am Post subject:
Great conversion Barnie and a beautiful roof

Milo

Joined: 16 May 2005
Posts: 342
Location: Oop North-ish.

Posted: Sat Jan 27, 07 9:21 pm Post subject:

Barnie wrote:

300mm width is fine and 450 to 600mm below top of foundations at it's highest point, .....

In which case I won't offer to dig the ditch for my elderly, wealthy next door neighbour who has what looks very much like ground water trickling into her cellar from about 1.3m below ground level!

Barnie

Joined: 26 Jan 2007
Posts: 40
Location: SW/Wales

Posted: Sat Jan 27, 07 11:05 pm Post subject:

Milo wrote:

In which case I won't offer to dig the ditch for my elderly, wealthy next door neighbour who has what looks very much like ground water trickling into her cellar from about 1.3m below ground level!

Hmm, probably not a good idea to buy a new shovel just yet, sounds like candidate for tanking or an indoor pool

Milo

Joined: 16 May 2005
Posts: 342
Location: Oop North-ish.

Posted: Sat Jan 27, 07 11:10 pm Post subject:

Barnie wrote:

Hmm, probably not a good idea to buy a new shovel just yet, sounds like candidate for tanking or an indoor pool

Now explain tanking. I've heard of it, but don't properly understand how it works.

tahir

Joined: 28 Oct 2004
Posts: 45669
Location: Essex

Posted: Sun Jan 28, 07 8:52 am Post subject:
Wow Nick, that's a stunning place, brilliantly done.

Penny Outskirts

Joined: 18 Sep 2005
Posts: 23385
Location: Planet, not on the....

Posted: Sun Jan 28, 07 9:19 am Post subject:
Stunning Nick

Gervase

Joined: 17 Nov 2004
Posts: 8655

Posted: Sun Jan 28, 07 9:23 am Post subject:

Tanking is where you apply an impermeable substance to the wall - either internally or externally - to stop penetrating damp. It's most commonly used with structures that are below ground level - in cellars or on walls that are built into the side of a hill, for example.
Ideally you want to do the tanking externally, but that isn't always possible.
Steer clear of any DIY stuff - you can get all sorts of bitumen-based paints and the like from stores, but they're all pretty useless. Ideally you need a sealed membrane or a proper waterproof render, and the usual materials used are Vandex and Newton 500, both of which will effectively seal the walls against water penetration.

Barnie

Joined: 26 Jan 2007
Posts: 40
Location: SW/Wales

Posted: Sun Jan 28, 07 12:23 pm Post subject:
Thanks all for your appreciation, and appologies to Armchair for temporarily hijacking his thread

Armchair

Joined: 14 Jan 2007
Posts: 205
Location: Winchester

Posted: Thu Jun 07, 07 8:54 pm Post subject:

Barnie wrote:

Thanks all for your appreciation, and appologies to Armchair for temporarily hijacking his thread

Not at all

Time to ressurect this thread...

I had a couple of damp proofing contractors in and they recommended (surprise surprise) an injected DPC. Now what they weren't aware of, and what I only discovered when chatting to my new neighbour this evening, is that the party walls (where the damp is predominantly found) is made of chalk rubble with brick piers. Probably a rather unusual form of construction but the row of houses is about 100 yards from a railway cutting so my neighbour thinks they used the free building material that was dug up there.

This begs the question, would an injected DPC be of any use and if not, what are the alternatives? Am I better off just leaving things as they are (on the basis that the walls have probably been damp for decades and aside from damaged plaster there don't appear to be any problems)?

Last edited by Armchair on Fri Jun 08, 07 6:37 am; edited 1 time in total

dpack

Joined: 02 Jul 2005
Posts: 46211
Location: yes

Posted: Thu Jun 07, 07 10:47 pm Post subject:
all i can add is that underground water can be a real problem to deal with above ground is as described above

MarkS

Joined: 01 Aug 2006
Posts: 2626

Posted: Fri Jun 08, 07 5:49 pm Post subject:
are there plenty of air bricks or have they been covered over. Im with Gervase on the whole no dpc injection thing.

Gervase

Joined: 17 Nov 2004
Posts: 8655

Posted: Fri Jun 08, 07 7:43 pm Post subject:

Chemical DPCs only work in bonded brickwork (sometimes!) - they most certainly do not work in rubble stone walls (it's down to something called 'viscous fingering' which means that the chemical takes the line of least resistance). If the contractors still recommend such a course once you've told them what the wall is made from, I would suggest politely showing them the door.
My advice would be to ensure a good air flow and to leave things as they are. Changes in drainage and ventilation are generally far more effective than mechanical treatments.

Armchair

Joined: 14 Jan 2007
Posts: 205
Location: Winchester

Posted: Mon Jun 11, 07 5:14 pm Post subject:

I spoke to both companies this morning and both said that injected DPCs on a rubble/cob wall wasn't going to work.

Company A suggested a quarter inch thick dimpled membrane to full ceiling height with plasterboard internally.

Company B suggested tanking with a cementious plaster!

Neither of these sound appropriate. I think I'll stick with improving underfloor ventilation and plastering with a lime-based plaster.

tahir

Joined: 28 Oct 2004
Posts: 45669
Location: Essex

Posted: Mon Jun 11, 07 5:15 pm Post subject:
You could try asking at AECB

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