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Posted: Fri Aug 10, 2007 10:20 am
by confuzatron
Hi,
When I got my new house, the mortgage company's surveyor recommended lowering the ground level out front, to reduce potential damp problems. Now I'm digging out the front to put in a new path, and want to deal with this issue at the same time.
I found this on another website:
"In the UK, the more traditional and more effective detail is to use a ventilated and drained 'dry area' around the foot of the wall. These are commonly covered with York stone slabs in order to prevent debris accumulating in the drained dry area and to minimise maintenance."
(http://www.buildingconservation.com/art ... ngdamp.htm)
Does anyone have any ideas on how to implement this kind of thing? Are there products produced to specifically build this kind of ventilation channel?
Posted: Fri Aug 10, 2007 9:19 pm
by lutonlagerlout
i think this is where the existing ground level is higher than the airbricks(common on old houses)
so they would have like a ventilation box
best to reduce the levels if you can
cheers LLL
Posted: Sat Aug 11, 2007 11:45 am
by matt h
agree with LLL lower levels. the dry drain is an old style boxdrain traditionally made in stone, creating gap between base of wall and surrounding soil. Worked on some fairly large buildings with these installed and as they have worked for centuries may suit your location, but what are your walls made up of? Are they solid, double skinned brick or what
Posted: Sat Aug 11, 2007 11:57 am
by matt h
what about a land drain? would certainly help IMHO
Posted: Sat Aug 11, 2007 12:28 pm
by lutonlagerlout
well what it is ,we now use telescopic air vents,but back in the day the vents had to be at least joist level beneath the wooden floor,which meant that the airbrick was often 150mm or 225mm below dpc
patios,paths atc were then done blocking the air flow unless you had this box arrangement
my pal with the larger patio coming up just reduced all his outside levels by 225mm because of this
regards LLL 
Posted: Sat Aug 11, 2007 7:21 pm
by Tony McC
Posted: Mon Aug 13, 2007 11:08 am
by confuzatron
Thanks for all the replies. The house is an Edwardian era sandstone building. There is a DPC in the internal brick walls (it looks like some sort of bituminous paper) but I don't know if there is a DPC in the exterior stone. Presumably not. Because of this, it's not clear how far the ground level might need to be lowered.
Looking at the quality of the stone used on the exterior, I think that maybe only a couple of inches more were intended to be exposed. Below that, it starts to look like it shouldn't be visible as smaller, rougher stone blocks are used. At the base of the wall there's a metal grill for ventilating the floor space, which was a 2 or 3 inches above the (not lowered) ground level.
I'm thinking maybe the low-tech (bodge) option as shown on the dry areas page is what I could use. The ground level will be lowered a bit, and instead of packed soil there'll be gravel against the wall, which should drain more freely. The path itself will be about 200mm away from the wall at the nearest point, and I'll haunch that to stop it moving.
I would lower the overall ground level, but unfortunately the new path has to meet the existing concrete path (original) that is actually slightly above the soil level, so I'm a bit limited in what I can do.
(By the way, this forum wasn't accessible from my home PC at the weekend - is there IP blocking? The site displayed a message paraphrased as "You are not permitted to view this forum, you're not logged in", and clicking the login link just directed back to the error message. I tried multiple browsers in case it was a cookie problem)