Condensation or Dew

[JFC]

I have a build area at the back of my workshop ,ive only had it for around a month so not had this problem before . I went out this morning and the roof was dripping with condensation or dew . Not good for a build area ! The roof is made from the plastic corrugated stuff from wicks . The walls are the back of the workshop the Garden wall and garden fence so in effect the area is out side and has lots of air flow but does get warm from the sun because of the roof . Any ideas what to do ? im not sure if its condensation or dew , so more airflow more dew less air flow more condensation !!!!!! #-o

 

[Jokerman]

Your shop sounds a very similar build to mine. Hot as hell in the summer, even with the windows and doors wide open.

I expect your problem is condensation. You don't mention what kind of floor you have in the shop and whether there's a DPC installed. Last night was a particularly bad night for condensation. Even the inside of my double glazed bay window was covered in it this morning, because of the air trapped behind the curtains.

The air in your shop will always contain a certain amount of moisture. Because the shop is protected it will cool down slower than the outside allowing warm and moist air to rise. That is until it hits the cold plastic sheeting where it will settle and condense. First off I'd have a look at the floor and see if you can prevent moisture rising up. In my shop I put in a suspended floor (3/4 chip on 4" treated joists) allowing plenty of air flow between it and the ground. So far no probs. Another way is a de-humidifier but they are dear to buy and run if you only make furniture as a hobby and aren't in the shop every day.

Hope this helps a bit but PM me if you need to chat about the problem further.

Good luck

Mike H

 

[RogerS]

I agree completely with Mike. Definitely condensation (dew would be outside on top of your roof). What is the floor? Concrete? DPC as Mike says? How old? If fairly new then there is a lot of moisture to pull out of the concrete and that will end up where you've found it.

 

[JFC]

Its the area out the back of the shop wich has a suspended floor with mdf on top that isnt fixed down so once covered in glue can be replaced . The area has an open end although sheltered from the wind and rain so is out side but it does get warm because of the roof . I suppose the only way to stop this problem would be to insulate or cover the top of the plastic sheeting stopping the warm air meeting the cold air :-k

 

[RogerS]

How about a vent at the rear wall so you get a throughflow of air?

 

[dedee]

I've just spent the last half hour os so trying to find a article I happened across a few days ago - and failed. IIRC the author was extolling the virtures of using small fans (the type used in computers and no more than 4"x4") in his workshop to suck the damp air out.

I'll carry on searching and if I find it again I'll let you know.

Andy

 

[SammyQ]

Snap! Got identical problems; when I built my play-pen, I installed 10' coorugated iron and corrugated clear plaskit sheeting simply because I urgently needed a fast, cheap roof. Bare iron like this drips something wicked and baling water out of a toolbox is something I NEVER EVER want to do again. My surveyor/building inspector relative told me the quick and easy way to combat it is to take off the corrugated sheeting, then lay 'chicken wire' mesh (2''-3'' spacing is fine) and then ordinary roofing felt on top, before topping off with the offending corrugated iron. An enhancement is to put spacers of about 3/4'' (cut from plastic plumbing pipe aka"hep" ) between felt and iron. This obviously does not work with clear plastic, but I'm experimenting with clear 800 guage DPM instead of felt. What I also did was cut batts of polystyrene cavity insulation into shapes that fitted between the rafters and wrapped them in offcuts of DPM before installing them. Provided you cut 'em a fraction too big, friction holds them up and allows you to adjust for an air circulation space above, to allow venting at the edges of the corrugated sheet/felt. I put mine up two years ago, intending to plasterboard the underside when I was satisfied over drips and leaks; so far none in an area 10' by 10' has come down, even with the odd dunt from a long piece of timber as I manoevered it into the shop. Hope this helps, Sam.

 

[WoodPecker]

Bare iron like this drips something wicked

There is a sheet material available now with a non drip surface, not sure who makes it, but could find out. There may be some way of coating the underside of the sheeting to make it non drip.

 

[devonwoody]

Does everyone realise this is a universal problem on our planet, substitute drips for rain.

 

[ike]

That's a bugger after all that work and expense. There's little you can do to prevent it unfortunately. Extra ventilation will help but not all the time. To minimise the occurrence of condensation for transparent roofing, the best material is double walled polycarbonate sheeting - shame it's so damn expensive.

Ike

 

[JFC]

There is masses of air flow as 1 side is open , no ends of the corrugated are sealed and another wall is mostly the back doors to a service road . Thanks for all the input . Taking all your input onboard i think the problem is the cold air is getting in as its lower at night (i think) then cant escape as the sun warms it up .
Solutions , fill the gaps up and spray the inside of the corrugated roof white to reflect the sun ? or black to hold the heat on the roof so the warm air is hitting a warm roof ?. I dont really want to put a solid ply and felt roof on because it backs on to the service road and i dont want to make it easy for any toerag to hop over ( rather find them splatted on the floor with a whole in the roof in the morning ) :lol:

 

[dickm]

If there's <any> surface within your shop that is at a lower temperature than the air, then you'll probably get condensation on it. If the surface is porous, it may absorb the condensation, but that won't do the material much good!
My guess is that your roof is "looking at outer space", (which is at about -273 degrees,) and radiating heat faster than it can take it up from passing air. So it's the coldest bit in the shop and painting it any colour won't help. How about a second skin of transparent plastic below the existing one? That wouldn't give your passing toerags much support, and the greenhouse effect of the two layers might mean that the inner surface was pretty near air temp. You'd probably still get condensation on the outer layer, but if it slopes towards a gutter, this could run away without harming things?

 

[PhilipL]

I replaced an asbestos roof with chicken wire, felt and corrugated iron roof. No drips. I live beside the sea and there was always dampness in the garage until I got a dehumidifier. Now, I work in the cold (well wrapped up) since cold without damp is no problem.

Philip