Damp-proofing in C16th cottage - bad idea?

[xanthe]

The cottage we are buying is a c. C16th timber-framed building on 4 floors, the lowest being a cellar that runs the complete length and width of the oldest part of the house. House sits on Wealden Clay.

The whole cellar is lined in dressed stone (disagreement between CO who says cellar is original and surveyor who says Victorian addition) and has a big damp problem.

This isn't helped by the cement pointing to the ashlar - the surfaces of a couple of the stones are starting to spall.

The surveyor says that an injected damp-proof treatment was carried out to the front and right-side party-wall elevations of the property in 2003 (and modern plaster applied). Does this mean it was applied to the first floor, or that it was applied down in the cellar?

Pretty much all the ventilation to the cellar has been blocked - either with bricks, or vast amounts of vegetation on the left gable wall at ground level choking the vents. Fortunately the ceiling consists of the floorboards of the main rooms above and nothing else. .

About a quarter of the cellar is about 7ft high with a tile floor (modern) with no grout and the rest has a solid concrete floor and is only about 5ft high at lowest point. There is a radiator in this part and it's much less damp. Where the tiled floor is, a ledge has been left all round the edge that is one tile high and one tile wide.

Ideally, we would like to take the whole of the cellar floor down to the 7ft high mark, re-point in lime, lay an appropriate floor (limecrete?) and get some serious ventilation into the place. Then we'd like to use it as a living-space (within the limitations of any under-ground room).

Before we do anything, we will have the appropriate people in to check that the house won't collapse! The LBO has already said that he doesn't have any objections to doing things in there.

Does anyone know what the reason would be for shoving up to 2ft of concrete over 3/4 of a floor? Is it dangerous to remove this?

Will try and find some photos.

 

[xanthe]

Here are some photos:

The bit where the boiler is etc, we don't have an issue keeping with the concrete in terms of using the cellar as it's the other half that we are after to turn into a room.

But, if it is contributing to the damp or may have a damaging effect on the building then we will take it out.

http://s1144.photobucket.com/user/helenmayer/library/Cellar

 

[billybuntus]

I have a very similar cellar and I've been running a small dehumidifier along with a condensate pump plumbed to a drain outside so I don't have to keep emptying it. I set the Dehumidifier to 56% RH and the difference is amazing.

I wouldn't bother trying to use breathable lime etc down there. It's underground

 

[Flyfisher]

I can second the use of a dehumidifier and condensate pump.

We have a smallish cellar that isn't used and we have no intention of using it as living space, but when I went down there this summer I was mildly alarmed to see large droplets of condensation on all the floor joists.

So I put our dehumidifier down there and it was collecting a full bucket of water every day. I quickly got fed up with emptying the bucket each day and bought a condensate pump ( about £50), which works very well indeed. It collects about a pint at a time and when full it automatically operates for 10/15 seconds to pump away the water. In my case I routed the outlet pipe up and out through an air vent and into the garden.

Within a few days the condensation had disappeared and the very musty smell had gone, so it has certainly been effective, though I'm not sure how practical such a thing would be for an occupied space.

 

[xanthe]

That sounds very promising! Do dehumidifiers potentially dry places out too much? Can you get thermostat type ones that you set to a certain level and they turn on and off to maintain that?

There is apparently a sump - although you can't see anything - but the surveyor was muttering things about it not being at the lowest point and maybe needing another one.

Is the concrete there for an actual purpose - like underpinning - or is it part of an attempt to reduce damp?

I've read that modern damp-proofing isn't a good idea in a very old building. Given that the house has been repointed in cement, the walls where the injected damp proofing was done have had modern plaster used etc makes me v suspicious that the work may not have been in the house's best interests.

 

[Flyfisher]

That sounds very promising! Do dehumidifiers potentially dry places out too much? Can you get thermostat type ones that you set to a certain level and they turn on and off to maintain that?

There is apparently a sump - although you can't see anything - but the surveyor was muttering things about it not being at the lowest point and maybe needing another one.

Yes, some (most?) dehumidifiers have a 'humidity' control. When first using ours, I set it to maximum in order to quickly dry out the condensation and it operated continuously, but thereafter I set the control to the midpoint and it happily switches itself on and off as required.

As an example, this is our model: http://www.johnlewis.com/de'longhi-des12-compact-dehumidifier/p230604725
I claim no particular market knowledge and don't know how it compares with others, but it seems to have worked well for a few years and I have no complaints.

An essential feature, for our use anyway, is a continuous drainpipe meaning that the internal water tank cannot fill up and cause the unit to switch off, though this does mean there needs to be another method of drainage and cellars are frequently below drain levels so there are various things to consider.