Cracks In The Ceiling
August 29, 2013 8:41 PM   Subscribe

Cracks in our concrete condo ceiling are leaking water from the channel to the dryer vent. Can we patch the concrete?

Our dryer vent in our condo unit is a channel in the concrete between our unit and the unit above. It runs about twenty feet with an 80 degree bend in it to get outside, where it vents over our balcony. When we run the dryer, we see water collecting at the vent and dripping out.

We have hairline cracks in the concrete along the channel, that appear to be normal concrete settling cracks to be expected in a nine year old building. Condensation is apparently building up in the channel and leaching out through the cracks when it gets too dense. When we moved in, the engineer doing our inspection pointed out foxing on our ceiling consistent with a water leak event, and advised us to keep an eye on it. It wasn't an issue until this summer, three years later, when the waterstained area became wet and started dripping water on our floor after we did laundry.

Tonight, the drop ceiling in our kitchen showed a water bubble that gave way when we touched it; I'd done two loads of laundry earlier that day. We pulled out a pot light and saw the same crack extending along the concrete there, along the channel's path, visibly wet and slowly dripping water, which I guess pooled and soaked through eventually.

After the summer incident, a dryer vent cleaning company recommended an expensive booster fan to replace the mediocre booster fan that came with the unit. We'll probaby do that, along with scoping the channel to see if there's any blockage (the vent guy physically probed the channel and pronounced it clear to the bend, and it had been cleaned by the same guys a couple weeks earlier as part of normal maintenance). But we're worried now that we know that condensation buildup is normal, and the crack extends where we can't observe dripping.

Is it possible to patch concrete cracks to reseal the channel? Is it possible to re-line or otherwise seal the channel to prevent water from getting into the cracks? Is there anything else we can do? How much cracking is normal in concrete? We're worried about our kitchen ceiling coming down suddenly.
posted by fatbird to Home & Garden (8 answers total)
Wait, am I understanding this correctly? The dryer is vented into a concrete channel / tube? I've never seen such a thing. Can you thread a proper pipe in the channel, and vent into that? You might have to do a bit of reno - a soggy spot can indicate water damage, and ongoing water damage can mean mold. Is this concrete channel vent a common thing in your area?
posted by barnone at 9:11 PM on August 29, 2013

Response by poster: Apparently a concrete channel is now a common thing. Before pouring the floor, they use pipe to lay out the channels, and then pour around that, casting the channel into the layer of concrete. It can happen that the pouring damages the pipe, partially blocking it--we're talking thin vent metal, not water pipe metal. It's not expected to be waterproof, though, and it's our bad luck that significant cracks intersect with it.
posted by fatbird at 9:16 PM on August 29, 2013

yea, that is kinda a messed up way to vent a dryer in that you can't fix it. I think barnone's idea is about the easiet way to fix it. To really patch it you need to get epoxy in the crack from inside the tunnel. If you apply it on the outside of the concrete it will only build up water behind it and cause a widening of the concrete, possible rust of the rebar in it (really bad news if you building is a pretensioned tiltup concrete building or a postensioned concrete building and most are) with the water and eventual failure of the patch due to hydrostatic pressure.

The other reason venting a dryer through a concrete channel is dumb is that you WILL get condensation because the concrete is cold, will cool down the dryer exhaust and give you condensation in a bad place (like you are finding out). You want that condensation to occur outside the building envelope, otherwise why vent it at all?

putting in some kind of liner will help with this problem. Short term the only other thing i can think of is running the dryer with nothing in it afterward a load to dry out the condensation in the channel. This is going to double the cost of doing laundry however. Talk to your building super/homeowners association about this. This is the kind of problem that leads to really expensive repairs down the road.
posted by bartonlong at 9:29 PM on August 29, 2013

Do other units in your complex have the same problem? This really sounds like a fundamental design error. Maybe there is some recourse against the builders. The proper installation would have been to use an insulated duct, but that's probably impossible to retrofit at this point.

You can patch or caulk the crack to prevent leakage but it is not going to stop condensation in there. I agree you need the booster fan, and running a dry cycle at the end of laundry day is also a good idea. Also, newer washers wring more water out of clothes, which means less water for the dryer to push through the vent.

BTW a nine year old concrete building should not be showing "settling cracks".
posted by beagle at 5:58 AM on August 30, 2013

I would get in touch with building management, this is a structural issue, not a cosmetic one and it's up to the condo association to deal with it. At least start there.
posted by Ruthless Bunny at 6:55 AM on August 30, 2013

Response by poster: Unfortunately, RB, I'm on council already, and they're not being... forthcoming with assistance on this issue. Aside from whatever mitigation we're considering, I'm also thinking of going back to the original inspecting engineer for an independent look at it.
posted by fatbird at 8:25 AM on August 30, 2013

Are you still in Vancouver? I bet there is a city agency that deals with building code stuff like this, especially after the "leaky condo" mess a few years ago. I'd try to track down some independent verification that this is, in fact, code, and how to fix it now. It just seems totally counter to everything I know about water and buildings. I'd really suggest not just patching up the concrete because it'll be a short-term fix at best, and you really do not want to be sealing up moist material above your ceiling.

There's a customer service number at the link above - maybe call that, and see where you get? Has anyone else in your building had the same issue?
posted by barnone at 11:57 AM on August 30, 2013

Response by poster: There have been various issues with the dryer vents for everyone, though none, to my knowledge, having cracks leaking water.

I spoke to my realtor, who put me back in touch with the inspector who originally noted the foxing. He agreed with various mitigations based on improving airflow, and confirmed that a degree of cracking is normal in all concrete construction (same as for poured foundations in houses). He said all the buildings are going in this in-concrete-channel direction to avoid drop ceilings and ventilation boxes. I have a feeling we're looking at the next leaky-condo issue. There are a variety of ways to repair the concrete, all of them intrusive and expensive.
posted by fatbird at 12:46 PM on August 30, 2013

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