Garage condensation....help...

[Soterik]

Ok...

I've got a nice steel insulated garage with zero issues, it's got insulated walls and roof, never had any problems.

To capture more space we closed in one of the carports on one side. A concrete slab was laid, the walls were insulated, but not the roof.

In the winter it's practically like it's raining in the newly captured space...but bone dry in the main building.

Any ideas on my next step? At this point I've got a project car in there and parts. I've laid a tarp on the concrete, and covered the car and parts with tarps.

Should I insulate the ceiling as well? Or would it just get wet?

Note that we didn't tear down the wall in between the main building and the newly "made" enclosed carport. Both have about the same amount of airflow in them, essentially a fair amount as I don't have things really well sealed up.

Looking to solve this issue before next winter.

The picture shows the original main building, and the "carport" prior to it being enclosed.

thanks,
Eric

[kaisen]

The new concrete slab is probably causing your moisture issue.

[daepp]

Did you use a vapor barrier under the slab?

[Porsche-O-Phile]

Exactly - bet there's no vapor barrier present. In a climate like yours, this is going to cause problems.

[Taz's Master]

It is certainly very possible that the concrete pad is causing moisture problems, but if the garage is heated, and the newly enclosed space is warmed from the garage, wouldn't the warm air condense on the cold uninsulated ceiling and drip back down? If that is the case, insulating the ceiling should fix the problem (just make sure there is ventilation above between the insulation and the roof). My moisture problems in my old garage caused by the concrete floor were usually not during the winter.

[Soterik]

Neither side is heated..

I don't know if the pad has a moisture barrier, my guess is that it doesn't. I didn't do the pour, I just did the excavation for the pour and did the form. I was gone during the pour which was contracted by the guy who framed it in for me.

Note that though I live in Seattle, and this particular garage is on the east side of the Cascades, and it's a pretty dry climate with very low humidity on the whole. Winters tend to be very cold and we do get a snow load on the roof. Sorry for that lack of information!!!

Any ideas for a type of vapor barrier for the floor at this point? Should the ceiling be insulated at the same time?

Info is greatly appreciated!!

thanks
Eric

[kaisen]

The moisture may also be IN the concrete slab. It will cure over time and dry itself, which it is doing now... that escaping moisture may be contributing to what you are experiencing. When it is fully cured things should be dry.

You might be able to wait it out.

I'd recommend ventilating the space with some sort of fan until then.

[onewhippedpuppy]

Originally posted by Taz's Master
It is certainly very possible that the concrete pad is causing moisture problems, but if the garage is heated, and the newly enclosed space is warmed from the garage, wouldn't the warm air condense on the cold uninsulated ceiling and drip back down? If that is the case, insulating the ceiling should fix the problem (just make sure there is ventilation above between the insulation and the roof). My moisture problems in my old garage caused by the concrete floor were usually not during the winter.

My exact thought, I saw this when I did remodeling. Even with just the walls insulated, you could easily be holding in warmer or cooler air than ambient, causing condensation.

If it were me, I would insulate the roof. From what I know, the bulk of the concrete cure occurs pretty quickly, I find it hard to believe it is still putting off that much moisture. If it continues, there's a variety of concrete waterproofing products, intended for basements and foundations, you could simply coat the floor with that.

[p911dad]

Eric, this may sound like a rube goldberg type solution, but I use it in a similar space in the winter, where I am not worried about how hillbilly it looks. The slab lacks a vapor barrier, so I lay a sheet of very heavy poly over the concrete, and then lay 4x 8 sheets of 1/4" plywood (cheap) over the top. You could always put a heavy concrete sealer on the slab, but it may peel up eventually. Or, lay down heavy poly and put another 3" of concrete over the existing slab with some mesh to hold it together(done that too, but concrete is out of sight($) around here!
Glenn

[Porsche_monkey]

Have you considered ventilation? A gable fan? Or some roof vents? Obviously damp air is condensing on the metal, just move more air.

[Soterik]

There's plenty of ventilation coming in from under the eaves. But I could install a fan pretty easily.

Can anyone tell me what effect the snowload in the winter plays into this... if anything??

Thanks for all the input. Definitely will seal the floor someway/somehow this summer. I did lay poly under the project car this winter to try to avoid any condensation under the tub during the winter, but I never checked it so I don't know the effect.

thanks,

Eric

[island911]

Yep, insulate the roof.

snowload is a structural thing, other than the condensation which will form on the underside of a noninsulated snowloaded roof. That is, just like a glass of ice water pulls moisture to it's sides, a noninsulated snowloaded roof will pull moisture to it's underside.

Make sense?

[Porsche_monkey]

I would insulate with pink styrofoam. And ventilate. This problem won't go away on it's own.

[Soterik]

Originally posted by island911
Yep, insulate the roof.

snowload is a structural thing, other than the condensation which will form on the underside of a noninsulated snowloaded roof. That is, just like a glass of ice water pulls moisture to it's sides, a noninsulated snowloaded roof will pull moisture to it's underside.

Make sense?

Understood......!

What's the difference in putting in pink styrofoam, vs. anything else? I assume that the pink styrofoam if it gets wet, it's no big deal. Any R value I should shoot for? Rafters are 2 x 10's.

E

[competentone]

Originally posted by Soterik
In the winter it's practically like it's raining in the newly captured space...but bone dry in the main building....

....There's plenty of ventilation coming in from under the eaves....

How is the roof of the "carport" tied to the main building?

I see a lot of problems with insufficient overlap -- and seepage of moisture from precipitation -- on metal roofs.

Are you sure you're not getting infiltration of precipitation --maybe running down a wall were it might not be real obvious -- that is the cause of what you're perceiving as "condensation"?

[island911]

If at all possible insulate with a closed cell foam. THe idea being you keep moist air away from the cold surface. This could be done with foam panels placed w/ the squirt-in foam around the edges. (leave a little weep/drain "hole" on the down side of each panel.

That's what I would do. Someone else may have a better idea.

fwiw, jets have a big problem with condensation. ...the outer skin get really cold at altitude, draws most all of the cabin moisture to the skin. The plane lands, the ice melts, and soaks the insulation blankets. The cabin refills with moist air . . . the plane gets heavier and heavier. (and you thought you had problems)

[Porsche_monkey]

I like the pink styrofoam because if it does get wet it won't be an issue. Wet rockwool is a mess.

I'd use pink styrofoam and a few cans of spray foam on the gaps. Or, go crazy and call foam spray company, they'll get it done in an hour.

I would also normally recommend a vapor barrier on the warm side, but I do not think that is a good idea here. I think outdoor the warm and cool side reverse in winter ans summer, so it's on the wrong side half the time.

Any builders familiar with this?

[daepp]

Even in very dry climates such as the desert communities surrounding Palm Springs, CA, moisture and water vapor can cause huge issues above the slab. If your contractor did not use visqueen or some other moister/vapor barrier I believe he is negligent.