Damp Steel Shed

Miss OMMC

Hi there,

We got an 800sq ft steel shed erected in October of last year. The walls have the non-drip coating on the inside and we added 25mm insulation boards ourselves after. It sits on an oversized concrete slab which has a DPM and is overlayed with the correct amount of concrete.

The problem we have is that on damp days such as today, it's dripping wet on the inside. We have a dehumidifier running most of the day and a couple of fan heaters if needed. The shed has a roller door which seems to let a lot of damp air in as when closed, leaves a big open gap.

Would anyone have any ideas as to what we can do to keep it dry?

CJhaughey

Miss OMMC wrote: »

Hi there,

We got an 800sq ft steel shed erected in October of last year. The walls have the non-drip coating on the inside and we added 25mm insulation boards ourselves after. It sits on an oversized concrete slab which has a DPM and is overlayed with the correct amount of concrete.

The problem we have is that on damp days such as today, it's dripping wet on the inside. We have a dehumidifier running most of the day and a couple of fan heaters if needed. The shed has a roller door which seems to let a lot of damp air in as when closed, leaves a big open gap.

Would anyone have any ideas as to what we can do to keep it dry?

The concrete will still be drying out, its going to be wet for some time until it dries thoroughly.

Joe1919

As far as I can see, this problem is often caused by the alternation of weather fronts. i.e. The cold dry air cools the steel and this is often quickly followed by a warm front carrying warmer humid air that condenses on the cold steel.
The old fashioned way of putting felt under corrugated galvanize (even on the sides) seemed to be a better job.

Bonzo Delaney

I wouldn't imagine the fan heaters are helping too much
Your just creating more warm air to condensate on the colder surfaces.
Is there any cross ventilation in the shed
I'd say during day the interior heats up and then in the evening/ night when the outside air temp drops the roof structure cools down and causes the warmer air trapped inside to condensate on the metallic surfaces including ther exposed foil face of the insulation.
I suppose by right you should clad over the insulation in 10 mm ply or similar and prob a breathable felt layer to the under side of the roof area saying that I've seen water droplets on the under side of felt in various sheds over the years but also found these sheds to have little or no cross ventilation whatsoever. Continuous ridge ventilation might hel sort your issue.