Very damp shed

johneym

Hi Lads,

There was a great big shed which came with this house.The shed is around 10 years old, 4 inch single block with a large steel sliding door.It a flat roof galvanize.It had a fuse box, spckets every 2 meters, 5 windows and floresent lights. I almost liked the shed more than the house!!
When I moved here a few months ago I discovered that many beems were rotton as the water seamed to be getting in somewhere along the roof. I repaired this an changed the beams.There didnt seam to be a leak on the roof though so I supposed that the water came down along the galvanize nails. The timber was untreated.
Now however, there is still so much dampness in the shed that it destroys, rots and rusts everything I put in it. Iv tried to leave the doors an windows open as much as possible to ventilate but if its a wet or foggy day I have to close them. The condensation in it is not normal.
There is talk here of Thompsons water seal. The shed is painted on the outside but could I still use this? Would all this condensation and moisture be really coming in through the wall? Any ideas?

Thanks a lot in advance,

John

Buford T Justice

There may be no DPC on the walls between the foundation and the walls, and you could have rising damp, or you could easily have a leak in the roof of the shed, the latter being more likely.

Have you anything in the shed generating heat that would cause large amounts of condensation on the galv roof?

johneym

thanks Fingers,

no i have not. As regards a leak I dont think so but its sometimes hard to tell as in damp weather the lights and everything else is dripping with water. What i assume to be condensation as everything has also this film of condensation.

John

john t

Damp course? or bad build.. floor not sealed? galvinised roof can rust or retain moisture.....

chenacross

Thanks for the great info !!!

slowburner

No insulation or breathable membrane on a galvanised roof will cause condensation. There also has to be a source of water for condensation - what kind of floor is it? Is there a dpc in the walls?

ART6

I had a similar problem with a single course block boiler house that I wanted to convert into a workshop when the boiler was removed. Inside it was permanently damp although it had a flat felted roof that didn't leak or cause condensation. So I dry lined it by covering the inside of the walls with polythene membrane held in place with 2 x 1 wood battens fixed with masonry nails. I then fixed 9 mm ply to the battens (it was cheaper and easier to handle than plasterboard, and it meant that I could fix things to it wherever I wanted). I used plasterboard in the ceiling, nailed to the roof beams.

On the unsealed concrete floor I first painted it with bitumen roofing mastic, making sure to bring the mastic over the bottoms of the polythene wall sheets, then when the mastic was semi-dry I laid lino over it and finally fitted skirting boards all round. The place has been as dry as a bone ever since (four years now).

slowburner

Great solutions.
What do you think was the source of the dampness in your case? The floor?
I'm sure this will be a help to the OP.

ART6

slowburner wrote: »

Great solutions.
What do you think was the source of the dampness in your case? The floor?
I'm sure this will be a help to the OP.

Slowburner I guessed that the damp was both through the wall (no DPC) and also up through the floor. Whatever, I wanted the wall lined in any case, and the floor had to be sealed with something to stop concrete dust that always rises from untreated concrete floors (and make it more comfortable on the feet!).

The ply wall covering lets me put things like surface mounted power sockets wherever I want, and it keeps the cables out of the way. Since the panels are screwed in place to the battens I can take them off if at any time I want to run more cables.