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I am looking for some advice as to whether the levels of moisture currently being extracted from my cellar are normal.

We have a large Georgian house (circa 1800) with a small keeping cellar off the kitchen. We home brew beer and wine so we keep quite a lot of bottles down there, and they have been accumulating mould and fungus, so I decided to try and reduce the moisture levels. As a first step I bought a dessicant dehumidifier (EcoAir DD322FW Simple) and have been running this for about ten days non-stop. I have attached the supplied hose to the rear of the unit and drain it into an 80l dustbin, so as not to have to go down to the cellar every few hours to empty the tank (and to ensure continuous running). I go down first thing each morning, and every day so far I have emptied a consistent 9-10 litres of water. I have also bought a humidity sensor, which read 95% before I started dehumidifying, dropped slowly to 74% over about four days, but has risen again slightly since then, reading 77% this morning.

The cellar is about 20 square metres, with an arched vaulted ceiling no more than about 2.4m at its highest point. It has a coal chute which is far from weather-proof, so allows some rain in, and a small hole low down in one wall through which a small amount of water penetrates, leading to very small puddle developing over time. The walls are whitewashed stone and the floor is flagstone. It lies beneath the hallway and a living room, but the steps lead up to the kitchen, and to allow the extension cable to run down there, I currently have to leave the door to the kitchen ajar by about 10cm. There are also small gaps in the cellar ceiling under the hallway.

To my mind, 9 litres per day is an enormous amount of water to be extracting. The house is very large, with approximately 1,000 to 1,200 cubic metres of air space, but even if the entire air space of the house were circulating through the cellar (which it clearly isn't) by my calculations the maximum amount of water that can be held in the entire house at 100% humidity is around 10 litres. Even if all the moisture created by cooking were to make its way down there, it wouldn't add up to anything like 9 litres. And it hasn't rained locally in about two weeks.

I am starting to think that I am actually trying to dry out the water table! In my naivety, I originally assumed that because we are on a hill of about 1 in 20, and 150m down the road is about 8m lower than us, the water table must be well below us, but I have since discovered that water tables are not 'level' and that they follow the topography of the underlying bedrock. Am I essentially paying £4 per day to run a dehumidifier that is NEVER going to get the moisture levels down to a reasonable level? And what would the solution be? If I were to tank the cellar fully, could I be doing more harm to the house than good, by forcing the water elsewhere?

I'd be very grateful for people's thoughts on the situation.

I am not an expert on this but I suspect that there is a degree of wicking of moisture permeating the walls and this , as well as the leak points you mentioned is leading to excessive humidity levels. I would firstly rig up some mechanical ventilation to suck the moisture laden air out to vent externally. The humidifier is fighting hard to keep up so sucking the damp air out will give it a fighting chance. My thoughts on tanking are that it will probably help considerably and as far as the where does the water go, it will find its way out somewhere else. Try a vent first, cheap enough at Scewfix for an experiment right up to the real thing https://www.screwfix.com/c/heating-plum ... t_by=price

DWD

DWD

Do not underestimate the huge amount of water that can be held in the fabric of the building, especially the floor.

A dehumidifier will do fine once the cellar has dried out, but only if the water ingress is minimal. If as you say there is water sitting just under the cellar then you will never dry this out with a dehumidifier.

So first thing is to establish, is there water getting in? If so, how much? Your coal chute needs to be sorted as well as any other obvious areas for penetration, then you need to turn your attention to the floor, it moisture coming up through the floor?

If there is moisture coming up through the floor you have two options really, dig it out and get a vapour barrier and new floor laid (the original floor is very unlikely to have a vapour barrier. Second option is to install forced air ventilation so the moisture that does come up can be pushed outside and an equilibrium with the outdoor humidity can be achieved. Which option you go for will be decided on by your budget but also your intended use case for the cellar. If you are happy for the cellar to be cold storage, almost like a shed then install the ventilation, it's easier and better in the long run but you will have to take measures to isolate that cold air from the rest of the house using insulation etc.

Have you tried using a damp meter on the surfaces to see if it’s all over a problem or just in some areas?

Thanks for the replies everyone. I have mislaid my damp meter; I'll try and find it soon, but it certainly feels like the floor is the main source of the damp. It sounds like rigging up some extraction is a good plan, to see what difference it could make. I'll give that a go.

leewhill wrote: ↑Tue Jun 15, 2021 2:46 pm Thanks for the replies everyone. I have mislaid my damp meter; I'll try and find it soon, but it certainly feels like the floor is the main source of the damp. It sounds like rigging up some extraction is a good plan, to see what difference it could make. I'll give that a go.

Give what a go?

Finding your damp meter

Or

Potentially wasting money on extraction?