Condensation in wooden shed

[David Germany]

I have a 5 meter by 2.5 meter concrete plinth in the garden, it has a polythene membrane beneath the concrete. On one half of this is a kit built summerhouse constructed from 28mm t&g with a 19mm t&g floor. Attached to this on the other half of the plinth is a lean-to shed constructed from 19mm t&g, this has no floor at present. My problem is that the shed suffers from severe condensation that forms on the roof and drips down onto the floor creating puddles. The summerhouse on the other hand never has any indication of damp whatsoever.
Could the condensation in the shed result from there being no wooden floor. The walls of the shed are sealed with flashing onto and over the part of the plinth that projects beyond the walls.

 

[EFLImpudence]

Would I be right in guessing that the summer house faces south and the shed north?

Assuming the roof (or anything else) is not leaking, you need to ventilate the shed.

 

[JohnD]

no floor? water may be evaporating off the ground or concrete.

The same thing is more often seen in old concrete floors with no dpm.

You could experimentally put down some polythene sheet, turned up round the edges to prevent rain falling on it. You can put paving or boards on top to walk on.

If water forms on the underside of the plastic, you know water is coming up. It might be the concrete is damp from rain, or from a defect in the dpm, e.g. at the edges.

 

[^woody^]

Is the summer house exactly the same as the shed only you call it a summer house?

Anyway, you need to ventilated the shed. Gaps around the side panel/roof junction normally suffice

 

[David Germany]

The summer house is approx 2.4m x 2.4 m 5 sided and effectively faces south, the lean-to shed is approx 2.2m x 2.2m and is attached to one wall of the summerhouse and sits beneath the eaves of the summerhouse with a 5 degree slope down to the guttering. I've installed vents on the front and back walls about 200mm below the roof.