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Mysterious effluence along wall in garage

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Apr 18, 2014, 08:14 PM
Mysterious effluence along wall in garage
I've encountered a problem, and I'm hoping someone can give me some idea how I might approach it. I have attached a .jpg with 3 pictures.

The first two pictures show an effluence that I found on the garage floor, running along a wall that separates the garage from a utility room inside the house. The HVAC system, water heater, utility sink, washer, and drier are all located in that utility room along the wall opposite the wall that partitions the utility room from the garage. So, none of those run directly behind the garage wall. Their plumbing is in the opposite wall.

The effluence looks very much like the road salt that is left in winter once melting snow and ice evaporates. Unfortunately, there is no reason to expect road salt right along that wall and no where else.

The last picture shows a blistering of the paint on the lower part of the drywall on the garage side. There is no blistering, staining, or dampness on the utility room side of that wall.

I have never seen that effluence before. However, last fall, I was “remodeling” the garage when I noticed some deterioration of the drywall in the same corner where, on this occasion, I see the greatest amount of effluence (picture 2). On closer inspection, I saw that the deterioration ran all along that wall, although not as pronounced as in the corner. I could not feel any dampness in the drywall. There were no water stains, neither on the garage side of the wall, nor on the utility room side, nor on the utility room ceiling. I have never had any occasion where the water heater, sink or washer flooded, sending water across the floor and to that wall. I figured perhaps the drywall, over a good many years, had absorbed moisture from the concrete. So, last October, I replaced a 12'x2' section of drywall along the lower part of that wall.

Today, I noticed that effluence on the floor along the wall. No wetness on either the utility room or the garage side of the wall. No wetness or staining on the cedar floor trim. But something is causing that effluence and that deterioration in the drywall. Possibly a leak inside the wall? But if it is moisture that is causing that blistering, wouldn't the drywall be at least damp? The drywall and cedar trim is completely dry.

Does anyone have any idea what this might be and how I might proceed to fix this?

Apr 18, 2014, 09:30 PM
is there by any chance a change in the roofline at that wall, like a setback garage? bad flashing at our house led to a pileup of driven snow and rain that worked down, ran along the roof deck, and came out the siding.

oh, and blew a piece of deck in the process.

temporary fix was two tubes of roofing goo, but when we redo the roof, we're going to have to have them flash that area properly and replace some decking.

sig: if this is a new economy, how come they still want my old-fashioned money?
Apr 18, 2014, 10:19 PM
What you are seeing is calcium from the concrete and/or ground water. You're getting some moisture there, but it could simply be ground moisture wicking up through the slab. Possibly a lack of moisture barrier in that area?

Not that big of a problem but also not that easy of a fix.

Apr 18, 2014, 10:35 PM
Temporary fix providing the moisture is coming up from the ground through the slab. Scrub the salt deposit off, allow to dry and then use a concrete sealer to that area. Secondly I would remove the baseboard, cut 1/4-1/2" off the drywall bottom to prevent wicking from the floor. If moisture is coming from above these remedies will not fix the problem and you will have to look higher for the source of water.
Apr 19, 2014, 02:42 PM
First, I want to thank you guys for the responses and, second, I want to follow-up:

Last Fall, when I replaced that 12'x2' lower section of drywall, I did leave space between the drywall and the cement floor. I also caulked between the cement floor and the drywall. However, this morning, I went ahead and did as redoverfarm suggested: I cut a 3/8” strip from the drywall bottom. I did notice that where the blistering on the drywall was worst, the drywall was closest to the cement floor (about 1/8”), which would support what Jaybee said about moisture wicking up. There was caulk at that point, which I thought would prevent wicking. I'm not sure why it didn't, but I do see that where the gap between the cement floor and the drywall was greater, there was no blistering.

I'm afraid that if I just leave a 3/8” gap between the drywall and the cement floor, dirt might accumulate behind the baseboard and, in effect, bridge the gap, forming a conduit. Do you think I should recaulk? I'm not looking to make work for myself, but I would like to avoid having to tear-out and replace another large section of drywall in the future. (This time, I was lucky that the blistering appears to be just a lifting of paint rather than a degradation of the actual drywall.) If you think it's worth caulking, what caulk would you suggest?
Apr 19, 2014, 03:59 PM
In this case, the caulk hurts, not helps. Better to have an open 3/8" to 1/2" gap than to caulk it as moisture can wick up on the outsides of the caulk. If there was only a 1/8" caulked space there then this is very likely.

You've got a baseboard which should limit the amount of dirt that can get underneath and fill the space under the drywall to a process that will take decades. Or, go ahead and caulk the baseboard bottom to the concrete - that will eliminate most all the dirt.

But cut out the old caulk at the bottom of the drywall. Keep that open air gap between the drywall and slab.

Apr 19, 2014, 05:41 PM
Because of that 1/8" gap that was caulked, I was going to ask if there was any possibility that caulk could act as a bridge between the cement floor and the drywall for moisture to climb. But I thought the question would sound dumb. Turns out it can! Many thanks, Jaybee.