Winter moisture problems in new attached garage
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Winter moisture problems in new attached... Expand / Collapse
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Posted 2/11/2007 8:09:03 AM Post #807
 

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For our new construction, the finishing of the drywall coincided with a winter cold snap, so I'm not sure which is to blame, but we have serious moisture problems in our new attached garage. The drywall is finished and textured, but there is not primer or paint yet, and frankly I can't see priming/painting with so much moisture. The bottom 2 ft. of drywall on exterior walls have soaked up water and the drywall is saturated there. There is also standing water on the cement slap all around the exterior walls, about 3 ft. in from the walls. I believe that is where the condensation is occurring, and the standing water is being soaked up at the bottom of the drywall. I should also tell you that, unlike a lot of new constructions, our garage does not have a 6" sill wall or water splash wall; rather the concrete foundation height is even with the slab. I was told this is allowed by code only for handicap-accessible garage slabs where the slab is even with the house's floor level. For us, it just worked out better that way due to the grade of the site and was not done for handicap accessibility, but nevertheless that qualified us for the low splash wall height, which we wanted in order to minimize the amount of exposed foundation on the garage's north elevation. So, since we don't have a splash wall and the drywall runs all the way to the slab (or about 1 inch from the slab), could this be what's causing the drywall to soak up all the condensation? Also, what's causing the condensation in the first place? Is it because we keep the house door open and warm air enters the garage and comes in contact with the cold garage walls? By the way, the garage is a 2x4 construction and it is insulated.

Here are some more questions.

1. At this point, with so much water in the drywall, what are the implications? Is the drywall ruined? Could it become ruined?

2. How can we get rid of this moisture? Heaters? Dehumidifiers? Fans? A combination? We've tried space heaters, but seems to have about as much effect as lighting a candle in a walk-in freezer.

3. Is there something that could/should have been done differently with the construction to avoid this? There is moisture barrier (plastic) covering the insulation and 2x4s before the drywall was screwed in place, but if that should have kept the moisture from wicking up into the drywall, then I imagine the plastic would need to have excess that sticks out underneath the bottom of the drywall, and that is not the case for the entire garage--just some spots.

4. I should also note that there are moisture spots along the entire garage where the exterior walls meet the ceiling, with one 4-in. spot wherever there is a roof truss. I suspect the roof trusses are conducting heat away from those points and cooling them so that the relatively warmer air in the garage causes condensation there. What does this imply? Is this normal for our situation, or are there construction issues that have caused this?

Thanks in advance for any helpful information!

- John
Posted 2/12/2007 3:24:48 PM Post #810
 

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Vieth (2/11/2007)
Also, what's causing the condensation in the first place? Is it because we keep the house door open and warm air enters the garage and comes in contact with the cold garage walls? By the way, the garage is a 2x4 construction and it is insulated.
Here are some more questions.
1. At this point, with so much water in the drywall, what are the implications? Is the drywall ruined? Could it become ruined?

2. How can we get rid of this moisture? Heaters? Dehumidifiers? Fans? A combination? We've tried space heaters, but seems to have about as much effect as lighting a candle in a walk-in freezer.

3. Is there something that could/should have been done differently with the construction to avoid this? There is moisture barrier (plastic) covering the insulation and 2x4s before the drywall was screwed in place, but if that should have kept the moisture from wicking up into the drywall, then I imagine the plastic would need to have excess that sticks out underneath the bottom of the drywall, and that is not the case for the entire garage--just some spots.

4. I should also note that there are moisture spots along the entire garage where the exterior walls meet the ceiling, with one 4-in. spot wherever there is a roof truss. I suspect the roof trusses are conducting heat away from those points and cooling them so that the relatively warmer air in the garage causes condensation there. What does this imply? Is this normal for our situation, or are there construction issues that have caused this?
- John

The condensation is because the slab/drwall temperatures are below the dew point of the air entering the garage from inside the home. Also cooling the garage over night condenses all of the moisture to the cool surfaces.  Stop allowing high moisture house air to enter the garage. Mop the water from the slab. Vent the garage with a small amount of outside air without allowing the temperature in the garage to freeze.  Suggest cracking a couple windows to allow the moisture loaded air to excape.  Any additional  short term heat will allow more venting which will speed up the drying process. Drywall can handle the water without warping.  After 4-5 days mold wll start growing on the wet surfaces.  Its important to get the dry process working ASAP. Because of the dry outside air, heat, air circulation and ventilation work will dry the garage quickly.  Call 800 533-7533 of you need additional suggestions. Keep us posted.  Ken  

Posted 2/13/2007 10:12:02 PM Post #812
 

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Good news! Since my last post, we quickly got things under control. I too thought that equalizing the indoor garage air with the outdoor air would get rid of the condensation, but that was not an option because we need to keep the garage warm enough for drywall texture to dry and for painting. Also, our builder wants to use the garage as a work space. So my solution was to use three 1,500W ceramic space heaters spaced strategically facing the three exterior corners of the attached garage. (The ceramic heaters cost $27 each at Wal-Mart.) Then I added three box fans, one behind each of the three heaters facing the corners of the garage, basically blowing the warm air into the corners (where most of the moisture was). Finally, I added a small Whirlpool dehumidifier near the front of the garage. We don't really have a need for it anymore with our Ultra-Aire 150H whole-house dehumidifier, but we bought it about 5 years ago for our old house, and I thought I might as well fire it up to help since we have no forced air vents in the garage for the whole-house system to help dehumidify, other than by leaving the kitchen/garage door open. It's removing about 1 gallon of water a day. I also swept up all the water. After doing all this, the remaining wetness that I couldn't sweep up dried up in less than 2 days. Now everything is bone dry, even the metal overhead door hardware, and the temperature/humidity near the front of the garage by the overhead doors is 66F/41%RH, which is fine for painting. This is probably adding quite a bit to our electricity bill, but I'm going to keep this solution in place for now so we have a good environment for painting. I'll dismantle everything when the paint is on and has had several days to dry and when the outside low temps are above freezing, which should be any week now. Probably overkill, but I'll burn a little electricity for some peace of mind, convenient/comfortable painting, and a good work space for our construction crew.

Thanks for your help!

- John
Posted 2/14/2007 7:43:48 AM Post #813
 

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Good to here from you!  I was concerned that you might have drowned.  Keep venting the garage as much as possible to allow the evaporated moisture loaded air to escape.  Dry outside air will replace it.  50 cfm of ventilation will remove 6 gallons of water per day.  After your experience, you are more of a moisture expert than most.  Thanks for sharing your episode.  Keep us posted. Ken

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