We own a house which has been built into a hillside, so the basement has one external wall and three walls partially or wholly cut out of the slope.

The previous owners 'tanked' the room using polythene sheeting as a membrane then plasterboard built on a wooden frame.

Inevitably, there is damp coming through - black mildew, by the looks of it. We think the membrane is partially to blame for this, as the brick retaining wall behind it cannot 'breathe'. Indeed, since we made a hole in the membrane, the smell of damp appears to have reduced.

Do forum members have any suggestions as to how we could deal with this in an eco-friendly way?

Apologies if this has been discussed before - I did try to plough through the old forum, but couldn't find anything relevant. Any advice very gratefully received.

Marion

Good grief. I have no idea. The basement is built of stone (salvaged from an old mill nearby, we suspect) with two floors of brick over. The internal wall holding back the hill at the rear is of brick.

The depth below ground at the rear is the entire floor, ie around 10' deep. At the front, you walk out onto the garden.

Soil conditions are neither clay nor sandy. Drainage is also a mystery, although the flower beds do come up to the stone walls.

There is a rudimentary damp-proof course visible in the one fully external wall. It's hard to say what is in place on the others.

Sorry to be so useless.

I had a similar experience, my back wall is cut into the hillside.
We hand dug using normal shovels - a trench 20 odd foot long and around
6 foot deep and 2 to 3 feet wide,(every so often after rain, bits of the sides
would collapse). Whoever build the bungalow had placed a perforated pipe
about a foot above the foundations, and then they spoil't the effort by back
filling the space with clay! Needless to say it didn't work.
We dug down to bottom of foundations, laid 6 inches of mixed aggregate
then replaced the field drainage pipe (after cleaning it) another foot of mixed aggregate and then filled the space with washed rubble, up to ground level.
Think of it as a French drain- the Romans built them they still work!
It works perfectly.

<blockquote><cite>Posted By: marionhaste</cite>We own a house which has been built into a hillside, so the basement has one external wall and three walls partially or wholly cut out of the slope.

The previous owners 'tanked' the room using polythene sheeting as a membrane then plasterboard built on a wooden frame.

Inevitably, there is damp coming through - black mildew, by the looks of it. We think the membrane is partially to blame for this, as the brick retaining wall behind it cannot 'breathe'. Indeed, since we made a hole in the membrane, the smell of damp appears to have reduced.

Do forum members have any suggestions as to how we could deal with this in an eco-friendly way?

Apologies if this has been discussed before - I did try to plough through the old forum, but couldn't find anything relevant. Any advice very gratefully received.

Marion</blockquote>

The important thing is to get rid of the damp.
Hiding it isn't a good idea.
Digging a hole round the building, wrapping the building in 1000 grade dpc and replacing the spoil with stones to aid drainage will work.

That's fantastic folks - lots with which to conjure, but much of it too scary for us to contemplate when it comes to diggin' trenches and finding foundations.

However, you have all confirmed my own views on the 'botched' tanking which is definitely making matters worse. I'm tempted at first just to rip it all out and see what happens - although I'm quite tempted by an electro-osmotic system too.

My old mum had one fitted in her house many moons ago and it worked a treat. Although that wasn't underground, the damp course - if there ever was one - was breached by the 'road' in front of it being higher than the floor level.

Has anyone had any experience of it? I'm not connected to the company in any way - I post this merely in case it is of interest to anyone else, as - as I recall - there was no disruption, no removal of plaster and no foul chemicals used. Mind you, I was but a lass...


Thanks very much nigel - I will be in touch, providing I can work out how to reach you!

Reply re electro-osmosis system:

Thank you for your enquiry.
yes, the Lectros (electro-osmotic) DPC system is available today (see attached).
It is designed to control rising damp at ground level but we are aware of successful installations below ground where the anodes have been installed in a grid pattern. It is important under these circumstances to ensure the cathode (earth rod) is below the lowest anode in the circuit and approx 2 m distant from the wall.
We hope this helps.
okease call for further advice any time.
Peter Fitzsimons
Technical Director
The Wykamol group
(Lectros International Ltd).

Has anybody had experience of installing a physical damp-proof course into an old (c1900) stone house? I mean the sort of damp-proofing which uses a layer of plastic membrane as is used on new houses. I appreciate this will involve cutting horizontally into the walls but just wondered if this was possible. I don't want any chemical injection and I'm dubious about the effectiveness of electro-osmotic and the porous tube system (Shrijver?). I've had a sample of my plaster analysed and there is rising damp. The worst effect of this is the smell of damp in the house which I'm desperate to get rid of. I'd be really interested in your views/experiences.

Installing a physical DPC is fraught with problems, particularly with stone. To quote Richard Oxley, one of the UK's leading authorities on pre-1914 buildings, "the successful installation of a physical damp-proof course is...extremely difficult or impossible and can also cause problems of settlement."
Taken from his 'Survey and Repair of Traditional Buildings' (Donhead, 2003), which I can't recommend highly enough.
You're certainly wise not to use a chemical DPC as these - even the modern gravity-fed cream treatments - do not work on most stonework, and are of dubious value even with brick (it's the cementitious plaster that is usually a condition of the treatment which keeps the damp at bay pro-tem, but not forever).
'Rising damp' per se is actually quite rare. Far more common is penetrative damp, which is often the result of raised soil levels outside the building, defective drainage and poor guttering. More often than not attention to soil levels and the instalation of a french drain will remedy the problem. It would certainly be cheaper and less risky than trying to instal a physical DPC.
Another common cause of 'damp' is the use of cementitious pointing and renders externally and cementitious or gypsum plasters internally. A stone wall needs to be able to breathe, and neither will help that. Furthermore, gypsum plasters are hygroscopic, and if you have moisture trapped within the wall, the plaster will suffer. With stone constructionm pointing, render and plaster should ideally be lime-based, with no cement.

I have installed several electro osmotic DPCs in stone walls up to 750mm thick where there is a rubble core. They work very well. The mortar in the wall becomes dry and very dusty when it was damp and sticky before. In one case a stone outbuilding which had green algae growing on the wall in a corner had been built against the wall which had a DPC fitted. After a month or so the algae died in a triangle from the top to bottom of the wall. I presume this was because the wall had dried out. If your walls are damp then it is likely that hygroscopic salts have risen into the wall from the ground. It will be very difficult to prevent these salts migrating into whatever new finish you put on the wall without installing a DPC. The problem is often made worse when the room is heated and the water in the wall evaporates because more water and salts are drawn up to replace what has evaporated. A correctly installed electro osmotic DPC will produce dry walls.

Before cutting or removing stonework (which, if the wall isn't ashlar, can be a beggar to replace, and you find the stones on the inside don't share a common bond line with the stones on the outside), I would suggest you consult a surveyor experienced in stone buildings (a rare breed - not every RICS member is). See http:////www.periodproperty.co.uk/cgi-bin/vendors/db.cgi?db=default&uid=default&view_records=1&quicksearch=1&sb=1&so=descend&sb2=18&so2=ascend&PScode=su&Region=---&x=12&y=9here for a listing. Failing that, get hold of a copy of Oxley's book.
Electro-osmotic damp-proofing is controversial. I have had to do remedial work on two houses that have had it fitted and have yet to see one property where it has worked. The one positive to this method is that it is perhaps the least intrusive and less damaging of the various methods of damp treatment to a building. It is also reversible in that it can be removed. The drawback is that it is not cheap and that if you do not have rising damp or it does not work you have wasted your money. Most systems recommend using a cementitious plaster with waterproofer, which is not advisable for stone construction. Certainly the BRE casts doubt on their effectiveness in its hefty work on damp: http:////www.brebookshop.com/details.jsp?id=145268. To quote:
"There are two types: active and passive; neither has been approved by a recognised laboratory. By far the greater number of systems are of the passive kind, where there is no external source of electricity. They have always been something of a controversial issue. On theoretical grounds, it remains a mystery as to how they can work; their effectiveness has not been demonstrated in the laboratory and field evidence is disappointing.
Active electro-osmotic systems use an external source of electricity. BRE has no evidence to suggest that the two types behave differently in practice, though some of the active systems may be rather susceptible to the effects of mechanical damage and electrochemical corrosion.
Installation is quick and relative (sic) simple in practical terms and involves, in principle, the installation of a continuous electrode in walls at DPC level. the system is either earthed through earthing rods set in the ground (passive types) or a potential is applied between the DPC and earth or between DPC and another set of wall electrodes set at a different level (active types).
The claim for passive types is that a damp wall contains an electrical potential and the earthing of this potential causes the dampness to fall. It is true that the existence of electrical potentials in a damp wall can be demonstrated. However, where such potentials are caused by the movement of moisture and salts in the first place, earthing the potentials might be expected to increase rather than reduce the upward flow of moisture and salts.”
The installations inspected by BRE were coupled with a replastering system which provided a good barrier to moisture; it is suspected that claimed successes for the system relied heavily on the render and plaster system. As far as is known the passive system is no longer available, though many thousands of installations still exist. Active systems do attempt to make use of true electro-osmosis: the movement of moisture through finely pored materials under the influence of an electrical field. Site experience is not encouraging and, again, the systems rely on the assistance of plaster to contain moisture.
Of the complaints about electro-osmotic damp-proofing that BRE has investigated, some have involved condensation problems that the installation could not be expected to cure; in others there appeared to be at least partial failure of the system, suggesting that electro-osmotic systems are not effective in preventing rising damp in walls in all conditions."

Far better to address the cause of the damp rather than to try to install barriers. Far cheaper, too!

Yes build a sump with a pump in it that switches on when the water rises. This can be inside or out.

Thanks for that, will investigate sump'n'pump systems.

Max

Try this link: http://www.periodproperty.co.uk/vendors.shtml and use the pull-down menu to find surveyors. Where are you based, as I may know of others in your neck of the woods.

You could also try W.R.Dunn & Co in York (01904 784421), who have done a lot of work on historic buildings, or Ryder & Dutton in Oldham (0160 633 0990), who work a lot with English Heritage and local conservation officers.

I've heard of an ASA ruling that went against Schrijver. Maybe they didn't add the magnets or install it on a waning moon.