Earlier this year we bought a 250 year old cob/stone walled farm house in Devon. It's uninsulated, has no central heating, the exterior has been covered in cement render and the interior walls with paper and paint. As you can imagine, we have some damp problems to work on

The kitchen, is an extension on one corner of the building, again with 2' thick stone walls and a brick floor. Currently is has vinyl flooring and old kitchen units and you can smell the damp when you open them. There's no heating and only a window for ventilation. The ceiling is sloping and slate covered.

I've been using a humidity meter/thermometer for the past week or so to see what it's doing and then looking at the dew point. Unsurprisingly, the humidity is high and the dew point is too. Using an infra red thermometer I've been taking the temperature of the wall/floor junction and it's always below the dew point.

I'm planning to take out the kitchen units and replace them. First though I need to fix the condensation problem. The kitchen is narrow and adding insulation to the solid wall is probably only going to make the damp wall worse plus would make it even smaller.

Plan is to put a cooker hood above the hob, venting through the roof to the outside, which would run whenever we're cooking. I'd add a humidity sensing fan, again vented through the roof, so that it would run automatically when the humidity is high. I'm thinking I'd use one of these http://www.rhldirect.com/store/warm-air-dehumidifier-kitchen-fan/ or the just the humidity sensing extract version.

Additionally, we have a spare storage heater that we could install in the kitchen to give some dry background heat during the day. The rest of the house has storage heaters on economy 7 so this would be a cheap way to add heating to the room.

This would give us humidity extraction and some heating which I hope would help. However, we would still have a cold wall/floor junction and my concern is that we'd still get moisture condensing there which would eventually affect the new kitchen cabinets. I though about having vents in the kick plates below the cabinets and then some sort of vent at the back of the work surface so that air could circulate at the back. Do you think this is a workable idea and where might I find some vent that would work in that situation?

Thanks for your advice.

I would be inclined to put external insulation on and carry the insulation down below ground to just above the bottom of the foundations (or down to 50cm in the unlikely event that you have any foundations that deep) and then back fill with gravel to form a french drain. Raising the temp. of the walls will also get rid of condensation and be better for the fabric of the building.
Hopefully FosterTom will be along to add his 2pennth.

Posted By: fostertomConsider a dehumidifier, must be the new dessicant type, not trad compressor type

Why? I thought the compressor type were more efficient

Any cabinets you fix to the wall will be affected by the level of damp and you are probably wise to consider them as a temporary installation until the walls are sorted, as the high moisture level will damage the usual chipboard cores. If you want to create an airflow try using units without plinths (or kick boards as you described them!). Okay, so you'll need to clean under the units more often, but with a gap behind the units you may keep the wall in a reasonable condition. May also be worthwhile painting the backs of the units to help seal them.

Of course the end game is to make the cob wall work as intended and remove the external render, but you will always have an issue with the wall being damper than other forms of construction as the cob can draw water from the ground - unlike any construction using cement mortar. If you want to create a dry internal surface consider using a specialist waterproof cladding held off the inside of the wall, creating an air gap, and then plasterboard or plaster finish. You will need to positively vent the air gap, but it will allow you to use standard kitchen units - albeit in a slightly smaller space.

We live in an old stone house that has mud mortar - after the war it was repointed in cement mortar and rendered internally. The moisture rises up the mud mortar and causes all sort of problems - especially where any furniture is set against the external walls. Impossible for us to sort the issues out so we just live with it and treat the mould on a regular basis! Of course building our new timber frame house will give us the warm, dry house for our old age! You have an opportunity to put the walls back their original condition - good luck!

Posted By: mr_magicfingersThanks for that. This afternoon I stripped some of the concrete render off the outside wall, a piece about 8x6'. The wall inside is damp, the mortar can be scraped with your fingertips. I think the next few weeks will see me taking it all off and assessing whether to just leave it off to dry out or render in lime. Fortunately Mike Wye is 10 miles from here and we'll be getting him round to give us some advice.

If it is an exposed wall I might be less hasty to rip off the render.

Cob may be different but my experience with lime pointed thick walls is that they breath yes but this just means letting in water when it gets wet every day Over the last week on the moors there has been a foot of rain most of which has been horizontal so all exposed walls just get soaked with little time to dry before the next lot soaks it again. The walls on the buildings here I treated in two different ways. One is now slate hung on the outside with lime plaster on the inside the other is lime pointed on the outside and has a plastic tanking on the inside. Both these solutions have worked well and let the walls breath but leave the occupants dry. Not really much help for quick kitchen fix thou.

For the kitchen could you fix up some PU insulation behind them with some gun foam being careful to seal the perimeter of the insulation? There is normally plenty of space behind kitchen units and just make sure the worktop is well sealed where it meets the wall. It wouldn't be pretty but no one will see it and easy to remove when you get around to a major overhaul.

Posted By: mr_magicfingersstripping the render patch off I found that the walls in that area are stone rather than cob, the cob may be higher up but I need to rent a scaff tower to get up there. Might change plans a little but the idea is the same I think. Also, yes, the rain is howling across the tops at us so that wall is now pretty soaked.

For the insulation, do you mean fix it to the back of the kitchen units and have a gap between it and the wall? That's a possible option I think, will have to take a better look at potential units.

Thanks for the suggestions.

For the insulation I was thinking of attaching it to the wall. If you seal it effectively around the edge the air cant get to the cool surface to condense.

Posted By: fostertomSo it's useless to try to reduce RH below outside RH.

It's useless to try to reduce AH (absolute humidity in g/kg or g/m³) below outside but you ought to be able to get the RH down if inside is warmer.

Yes Ed, that's more accurate

If you draw in cold air and warm it up, the RH lowers. So you may have a problem in the summer if your house is colder than outside and the external RH is already high.

Yeah but esp in spring and autumn, outside air has v high abs concentration of water vapour; inside may have less even if it's condensing; internal cob wal surfaces may well be colder than outdoors. In those cases, at those times, importing outside air makes matters worse.

MVHR and porous external lime render, coupled with a land drain around the outside walls. Keep inside wam.

Mechanical Ventilation and heat recovery. Basically incoming ventilation air recovers heat from outgoing stale air via and air to air heat exchanger. The basic principle of the land drain is a trench all around with a drainage pipe in the bottom with slots or holes in it to accept water underground. This pipe should be plumbed to a drain somewhere. This is buried in gravel and can be topped off with a textile layer that stops soil etc blocking the system up but letting water through. I also usually water proof against the building foundation/lower wall leaving the higher areas with a moisture porous render to let any water in the wall wick away.