Corrugated Garage Roof

[Shepherduke]

  I should probably be enquiring on a "Builders" forum, but here goes anyway.
My garage, which is where most of my DIY and hobby activities take place, has an asbestos corrugated roof. The problem with that is, it is freezing in the winter, and as hot as hell in the summer.  The real problem is condensation, and I wondered if anyone has a simiar problem and how they cope with it.
  Apart from fitting central heating in the garage, I'm stumped as to what I can do. I intend making an insulated  box for my lathe ( similar to the ones that covered the old sewing machines, so I hope that will stave off any corrosion problems.
Should my six numbers come up this week, I will post pictures of my new workshop ASAP, but don't hold your breath!
 

[Andy]

My garage (which is not my workshop, unfortunately) has a roof like yours. Yes, it gets hot in summer, very cold in winter, but I never get any condensation. There are a lot of air gaps in the eaves of the roof and around the main door which I've never got round to sealing, so I'm thinking you need to look at ventilation.

[Darren]

The biggest cause for wet roofs on the inside is no DPC under the floor. The water comes from underground driven by the heat (I say heat, it only need a few degree rise each day from the low night temps)
Then as this water rises it hits the cold roof forms droplets and falls.

And so the cycle starts again. Ventilation is one answer and lots of it.

The real cure is to dig the floor up and re-do it.


For the heat problem in the summer, and it will help the condensation, reline the roof on the inside with ply. Insulate it you can afford it as that will help too.

[Shepherduke]

  Thank you, I'll try the ventilation theory first, as it would be cheaper if it works. 

[Darren]

The trouble with ventilation while it will help is that the floor has a never ending source of moisture. As this rises it will be carried out through the vents, but it will also condense onto your machinery on the way up.

Ventilation will cut it down quite a bit as it stops the rain cycle. But it probably won't cure the problem fully.

[CrewCab]

How are you heating it, if for instance you are using a small gas powered space heater it will be fine for 5 minutes and then you will think it's the monsoon season      ............ as butane and propane contain a lot of moisture, electric heating is "dry" and will avoid the condensation problem but, it's more expensive.

If your getting a lot of condensation with no heating then I'm confused 

CC

[Darren]

I get a lot of condensation on my larger machines with no heating. And I have gone to great lengths with sealing the place and insulation.

For example, My DPC water membrane is under the insulated floor slab and goes half way up the walls in one piece. The block walls have a membrane in the lower coarse to stop damp rising from the ground. Then I have built a stud partition on all walls, insulated with 75mm foam boards with silver foil on both sides (water proofer as well as heat reflector)
The ceiling has 100mm insulation boards and plasterboarded. The roof has a waterproof membrane and is slated.
The doors are also insulated and lined on the inside.

As you can see, I have gone to the extremes to keep the place cosy and dry. But still it condensates on the big lumps of metal and rust forms quickly.

But stick a heater on, I keep it to around 10deg, and the moisture all disappears. Problem solved. If I had not DCP'd under the floor slab then heating would have made matters worse as water would have been pulled from below ground.

Next year I hope to have the underfloor heating connected .... 

Indecently, due to all the insulation using a small electric heater on a thermostat it can get it from, taking a recent example, 5deg to 12deg in a very short time. Around 15-20min. After that the heater is hardly on. Just clicks in now and again.

I'm finding 12deg a little too warm when working, with a coat on anyway, so may turn it down a touch.

When I made that arbor, say an hours lathing the temperature of the room shot up to 16deg and I was too warm !! It also stayed there for the rest of the night from what I remember.

You may have guessed I don't like the cold 

[Bluechip]

I have the same problem in my concrete garage. This does have a membrane underfloor, not that it does any noticeable good.

Damp air gets in through the d-shaped holes under the corrugated roof and cannot get out. So, as warm air holds more moisture than cold, it says in the air until it contacts any surface below the dew-point, depending on the temp. and relative humidity, then condenses on that surface. Usually metal.

Using any gas burner for brazing or heating slings out a lot of water, as has been stated. I'm not a novice in drowning in condensation  

http://www.homemodelenginemachinist.com/index.php?topic=4929.0
See the reply by Ricks son, a few posts down. 1.7 ish kg of water per kg of propane. That's 1.7 liters too.

Not to mention we humming beans breathing out H2O. I don't know how to avoid that .. no suggestions either, if you don't mind  

Some 20 yrs ago, one of my friends had a Emco (Super 11 ??) That had a boxy section bed. It was rusting like the clappers, so ..
I had lots of 3 ohm 25W Alloy clad resistors doing nowt so we attached the to the machine bed, spaced out, wired 6 I think (?) in series from a 240V/12V transformer.  The bed was kept warmish, but other kit he had still rusted, particularly the Record vice, but not the Emco. Only vaguely warm, but enough.

A de-humidifier will fix the problem, but, as in my case, it's pretty much futile unless I bung up all the holes and stop the wet air getting in. Which is damn near impossible with my concrete garage, 'cos b**gger-all fits properly. QED.

Dave BC

 

[Stilldrillin]

Re condensation/ ventilation..... The underside of my carport roof, at dawn today.




I can`t imagine a better ventilated area than a carport......  

David D

[Shepherduke]

  Plenty to think about there. I live in Cornwall, so that may be an added reason, with the damp air.  I have made enquiries with management regarding the siting of the new lathe in the centrally heated sitting room, but received a rather rude reply!  Problems, problems.

[Darren]

Well David, that de-bunks the ventilation theory ...

I did wonder that whilst the ventilation may remove water logged air, it might also bring in new damp air ...

[andyf]

There seems no logic to the condensation question. I have a brick garage with a tiled roof, built in the 1930s so there probably isn't a membrane below the concrete floor. There are two airbricks in the walls, and plenty of leakage round the main doors and side "courtesy door".

In the 35 years I have lived here, I have never had a problem with condensation, or with unprotected items rusting unduly. Three years ago, I screwed a chipboard ceiling up to the roof joists, with insulation on top, and built internal stud and chipboard walls, again with insulation behind, a couple of inches in from the brickwork to leave a gap for air to circulate behind via the airbricks and the gaps round the main door. I worried that sealing up my working space like this might promote condensation but there still isn't any, even though it's pretty humid round here with frequent heavy dew overnight and a fairly high water table.

Andy

[CrewCab]

There seems no logic to the condensation question.

It's a case of getting the balance between insulation and ventilation right ............ and as you say "no logic" is involved afaik ........... it's a bit of trial and error I'm afraid 

CC

[Darren]

Now that I have stuck a heater on all my condensation problems have disapeared.

I'm using the lowest setting on the heater which is 400W which is also controlled with a thermostat to 12deg. Where I like it 

I have tonight put a meter on it to monitor the electrical usage .... will report in due course, but it's unlikely to be much due to the insulation measures.


"Snug as a Bug"
Darren

[Divided he ad]

Quick searched science lesson..... 


http://en.wikipedia.org/wiki/Condensation


Read at least this paragraph and I think we're all better of in the knowledge stakes!?

Water vapor that naturally condenses on cold surfaces into liquid water is called dew. Water vapor will normally only condense onto another surface when the temperature of that surface is cooler than the temperature of the water vapor.

Just thought a bit of knowledge could go a long way into understanding your issues Kevin.... Oh hi BTW 







Ralph.

[Shepherduke]

 Thanks to all.

[Darren]

On the electrical heat costs,

400W heater in this cold snap which is currently around the freezing point is costing about £1.50 a day to keep the place at 10-12deg if left on 24hrs.

If turned off overnight and only switched on for about 10hrs a day then the cost is just under half that as you would expect.
When off overnight the temp at the start of the next day is hovering around 6C.

I can live with 75p a day .... 

[ksouers]

Darren,
Wouldn't you want to flip that time around? Run the heater at night and let the sun (when you can get it) keep things warm during the day?

Say, come on about 8-9 PM and off again 12 hours later...

Just thinking out loud.

Kevin

[Darren]

I don't know where you are in the US but here in the UK we will have forgotten what the sun is by the next time we see it !!

The days are incredibly short now and it starts to get dark around 3.30 in the afternoon if it's cloudy. If the sun is miraculously out and shining merrily it's so low on the horizon there will be no heat worth mentioning.

Nice idea, but won't work here 

Estimated useful sunshine around end of Feb next year. Which along with Jan is our coldest months.

Those further North of us have it worst, not a good time for Scotland beach bathing I hear .... 

[ksouers]

LOL Darren. I didn't realize Merry Olde England was that far north.

I'm in St Louis, right about the middle of everything from every direction, latitude 38. We get some sun in winter, not a lot, but sometimes enough to warm up the garage where my shop is. Definitely a difference (sometimes) between night and semi-day, temperature wise.

Kevin

[Darren]

Wow, you're just about between Spain and N/Africa ..... bet your summers are warm 

[Majorstrain]

You can have some of my sun. 
On an average summer day (just about now) the temp in the shade is 35°C and the temp in the shed gets to the mid 40's.
It's usually 7:30pm b4 I can get into the shed to do some work and by then it's still low 30's and the machines are hot to the touch.
We'll get a week of low to mid 40's in February. That's a good time to visit the relatives in Albany (35°01'S 115°53'E)
I should point out that I'm not complaining, I makes for beautiful evenings and the air conditioner takes care of the heat in the house.
Just thought I'd be generous.

p.s. Corrugated iron roof and walls on the shed, not insulated and no real problem with condensation in winter (equivalent to an English summer )
Cheers
Phil
31°57'S 115°51'E  (Perth - Western Australia) That's the big island that counter balances the world so it doesn't topple over and through us all off. 

[Stilldrillin]

Thanks for that Phil! 

It`s 15.20 hrs...... I`m just thawing me hands & feet, after 3/4hr in the workshop at 2*. 

Just a little bit of your sun would be very welcome! 

David D