To tank or not to tank?

[Footdoctor]

Hi All.
This is my first post so bear with me if I haven't put it in the 'right place'. :|
I am currently renovating a 18thC cottage in W. Yorks and am not sure how to dry out the cellar.
The cottage is on a steep hillside and the rear wall of the cellar is actually above ground.The space has two rooms but is irregular in shape as it was formed by 'squaring off' section of the hillside.
There is a small window in this rear wall which has been boarded over some years ago. I have wedged this partially open now in order to increase the through draft and it is not massively damp but needs to be dried out further to be of use.
As the space is solid stone with one small area of 18" thick wall, I wouldn't have thought it is suitable for modern tanking methods.
The walls are irregular and unsuitable for rigid lining. I am keen to utilise this space and would welcome any suggestions, other than using a dehumidifier indefinitely.
Cheers
The Footdoctor

 

[middi]

Hi and wellcome.

By increasing the natural ventilation a cellar has many usefull uses.

If you intend to put your cellar into " living space " use then you have no choise but to take control of humidity or heat control of that space. Every cellar has it's character and no two cellars are the same regarding the amount of intervention required for them to be used as living acoomodation.

It would be best for an experienced ( local) builder to take a look and pass on his/her comments as to what would be the best course of action to take to suit your needs.

Middi

 

[Penners]

Welcome, Footdoctor

As Middi says, cellars are all different, so it's very difficult to offer specific advice about yours - particularly on the basis of a written description.

But there are general principles that will always be beneficial in trying to dry out a structure. It's not possible, however, to forecast how successful they'll be.

Dealing with damp can be a long process. There are many things to try, and you're unlikely to know the efficacy of each action until a long time after you've implemented it. So, given that some of the steps can be pretty costly, it's always best to start with the cheapest solutions. Try one, wait a few months, then re-assess (with a cup of tea and a Kit-Kat, of course).

1. Again I echo what Middi said: warmth and ventilation are great damp reducers - but you must have both. Warm air holds much more moisture than cold air, so the idea is to create warm air to mop up the damp and then to blow it outside (not cost-free, but usually effective).

2. Are you sure that the masonry structure is sound? Are all mortar joints and pointing in good order? If you need to re-point any areas, be sure to identify what type of mortar has been used - if it's lime, then you must re-point in lime. If you find that cement pointing has at some point been inserted over the top of lime mortar, then you will benefit the building if in due course you plan to rake out the cement pointing and replace it with lime mortar.

3. Are you happy that all water management fittings - gutters, downpipes, plumbing, drainage - are functioning properly and watertight?

4. How practicable would it be for you to dig a trench between the uphill wall(s) of the cellar and the external soil? Keeping the soil away from the walls is invariably beneficial in reducing cellar damp. But you may have to make provision for the water to be channelled away at the base of the wall by a French drain, or something similar.

As I said, start with the cheapest of those suggestions, and give the wall plenty of time to tell you whether it's feeling drier or not. There's a rule-of-thumb that says every inch thickness of damp masonry wall needs a month to dry out properly (once the source of damp has been removed).

Do keep us posted on your progress.

 

[Footdoctor]

Thanks for your replies and advice.

I think the place to start will be some re-pointing and reinstatement of the terminal section of the down pipe, assisted internally by the dehumidifier.
I wondered about a layer of damproof membrane on the floor only in the meantime to protect anything stored on the floor level.

The property backs onto a graveyard so I won't be able to do any digging!! :shock:

 

[MatthewC]

Hi Footdoctor - you are in the 'right place'.

The advice from Middi and Penners is very sound standard advice which you won't really improve on without an on-site inspection. I followed these principles with my property last year (see my blog at http://houseintheenchantedforest.blogspot.com, especially the label for "dampness"). One that Mr P mentions is the use of (impervious) cement instead of (permeable) lime. I apologise for the impertinent question but can you tell the difference between cement and lime? When you re-point, it is most important not to use cement products on a breathable wall, which is what your 18th C cottage originally would have had - I wonder if it still does?

I think the place to start will be some re-pointing and reinstatement of the terminal section of the down pipe, assisted internally by the dehumidifier.

You didn't mention that fault before! Check all possible sources of water ingress and fix them before trying any other fixes - no amount of ventilation will sort out the constant ingress of water from a broken gutter, roof or downpipe.

I wondered about a layer of damproof membrane on the floor only in the meantime to protect anything stored on the floor level.

I'd argue against that as it will inhibit the evaporation process. I suggest you use a few bits of treated 4x2 with some boards on top to support everything a couple of inches above the floor.

Just to clarify, the rear wall of your cellar is the uphill wall? Is the uphill ground level above the floor level inside? It needs to be six or more inches below to avoid a damp floor.

Before anyone else asks, any photos please?

 

[Penners]

I agree with Matthew about the floor. The problem with making it impervious is that - as he said - you impede the evaporation of dampness, and if the damp can't get out it can tend to travel sideways into the walls.

If you're just going to be storing things, I would definitely arrange simple structures to keep these off the floor.

 

[Footdoctor]

Hi all
Sorry for the tardy reply but its all gone a bit mad here in Manchester! (no, not the riots) So, if there are gaps in correspondence, it's not because I'm ignoring you. :wink:

I apologise for the impertinent question but can you tell the difference between cement and lime? When you re-point, it is most important not to use cement products on a breathable wall, which is what your 18th C cottage originally would have had - I wonder if it still does?

I suggest you use a few bits of treated 4x2 with some boards on top to support everything a couple of inches above the floor.

Just to clarify, the rear wall of your cellar is the uphill wall? Is the uphill ground level above the floor level inside? It needs to be six or more inches below to avoid a damp floor.

Before anyone else asks, any photos please?

Cheers Matthew, a couple of points to reply to:- Yes, I do know the differences with lime and the dreaded concrete and will be re-pointing in lime, luckily there is very little in the way of concrete pointing on the walls. I too have lovely new, lime plastered walls. Expensive, but worth every penny!

The 4x2 idea plus a dehumidifier sounds like the way to go in the short term while get on with the main cottage.

The arrangement of the cellar is very hard to describe 'on paper' because it really is just a hollow in the hillside squared-off, with the cottage is built on top.
The rear wall is on the down slope and is technically above ground and the other walls are formed from the contours of the hollow.
I now realise that I do not have any internal shots of the cellar but will post some images as soon as I have them and have worked out how to do it!
BTW, Matthew, very impressed with your blog, some of it very familiar. :roll: Your motivations and circumstances are exactly the same as mine, though a lot more grand

The membrane idea...I was really just 'running it up the flagpole'. I knew what the answer would be but, I suppose I was just looking for confirmation and hoping (vainly) for a simpler solution. :wink: