Help needed

Chris jr said:
I worked with surveyors and damp specialists for decades. It's all about ventilation, not insulation. You shouldn't need a dehumidifier unless you're generating moisture. Water has three main states 1. Water. 2. Steam (airborne). 3. Ice. A sink, cold water tap will be fine (no steam, occasional kettle maybe).

You can heat the internal space occasionally, it'll warm the space and 'purge' airborne moisture, but generally the internal temp should match the outside with no issues and it'll stay dry. My 6 x 3 meter wooden shed is always moisture free and nothing has rusted (three 2 strokes, carpentry machinery) because it's well vented.
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*2. Vapour.
Steam only exists when water is being forced to vapour outside of normal conditions. Steam is typically vapour under the influence of temperature and pressure.


But there is one thing to note in general. In our middle of the road environment, water only wants to do one thing, and that is to become vapour.
It’s more likely to become vapour when conditions allow, ie , warm temperatures ‘create’ greater space in the air for vapour to exist, and the warmer temps will encourage water to change its state to vapour. Exactly the opposite occurs in colder ambient temperatures, the air being more densely packed has less available space to contain vapour, and colder temps means water is more reluctant to make that change of state.

In more extreme environments, say the tropics, water vapour trapped in air ( humidity) is extreme, in the polar environments where temperatures are below zero, the air is so cold and densely packed, there is little or no humidity, as water vapour has nowhere to exist.
 
I think the key to this will be making sure no water, in any state, gets in there. Ventilation will only work if the air drawn in has less water in it than the air inside, which given the UK climate is going to be rare. Of course you will need to breath, so some air change must take place. You don't have to run a dehumidifier 24/7. I used to run one on cheap rate only, set to lowest level. The humidity would rise during the day but was restored overnight. As long as it remains below 60% I don't think there will be a problem. For a dehumidifier to work the air temperature will need to be over 10C, otherwise it will ice up and do nothing.
 
Slowly coming together hopfully finished end of April.

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Sarge said:
Ventilation is a must.
And possibly insulate the roof/ceiling.

A frost heater might be of benefit, I had one in a similarly built but smaller armoury and that kept the rust away.
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Dimplex used to do a really good one years ago, kept the caravan from suffering over winter.
Zinsser is good paint for keeping moisture and mould away.
 
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Winter in the UK has influences on how we build or at least it should do. From my experiences in the workshop the biggest enemy is surface rust on materials, hand and machine tools and the general deterioration caused by atmospheric water vapour condensing on all cold surfaces. Humidity reduction is the best solution IMO. How that is achieved is well know in the industry. best insulation between the inside and outside surfaces, ventilation which sadly conflicts with heating, best to get some advise from an expert, dehumidification which I am a big fan of and does not cost a fortune these days. good luck
 
Do you know if there's a damp proof membrane under the floor? Our old garage used to suffer from damp floor without one, it would make the paint lift.
 
James1966 said:
Do you know if there's a damp proof membrane under the floor? Our old garage used to suffer from damp floor without one, it would make the paint lift.
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Not sure but before painting i didnt notice anything. The previous paint did show signs of crumbling in spots but it was more than likely 10+ years since it was painted last.
 
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