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Help solve my mystery... Water or condensation intrusion

elliottheperson Member Posts: 3
edited July 2023 in THE MAIN WALL
Hi good folk–
I’ve got a good old conundrum for you all. I’m not sure what to do and could use your advice! Sorry for the length…

I arrived to Los Angeles three months ago to assist my grandparents in putting their 1960 flat-roof home back together after winter flooding.

A separate, but big issue presented: there's been persistent water entry (perhaps for months or years) along where the ceiling meets the chimney. I just had the roof replaced and new flashing was installed on the chimney (I don't know if they chiseled into the brick/mortar to install the flashing).

On the ceiling, next to where the ceiling meets the chimney, there's an HVAC supply register in the middle, a return on the far side, and a window next to the return.

Here are photos and video

I’m not sure if it’s a separate or related issue, but when I got to the house three months ago, I saw that there was water intrusion near four other supply ducts in different parts of the home. We repainted ceilings about three weeks back and I haven’t seen further evidence of water/condensation. (When we reroofed, the duct boots were resealed).

Here’s a map of where those duct boots are:

I'm not quite sure what the issue is, but from doing some research, I wonder if it might be one of the following:
1. Perhaps there's a lack of proper insulation in the outdoor ducts or the supply/duct boots. This supply duct has a lot of hot and maybe humid air when I stick my hand up into it. I haven’t used the AC for months. An HVAC guy says the temperature within the ducts and supplies/boots are about 100 degrees, and indoor temperatures now about 60 degrees. The ductwork is at least 15 years old:

2. Improper ventilation in the attic -- it's a flat roof, and there's no roof fans and I don't see any gables/vents around the building
3. B-vent from water heater not venting properly...as you can see, in addition to two flues for two fireplaces, there are two vents on the chimney...one which used to go to a furnace which has been not operational, and the other from the water heater, which is in use.
4. Cracked grout between bricks of the chimney...maybe water or moisture is getting inside, but I also see the water entry on dry days (maybe the bricks are retaining the moisture). (A chimney guy said it’s not this)
5. An open or damaged damper (A chimney guy said it’s not this)

I have just about a week left here until I have to fly home and go back to work, so I’m trying to throw everything at this. I know that I’m moving a bit too quickly, and not giving time to isolate variables…

Last Thursday, I opened up the ceiling a bit and felt moisture where the supply is.

On Friday, the gas company found a couple gas leaks so they shut off our gas. Which means the water heater has been off since Friday.

On Saturday, I added caps onto the chimney and had one of the flues extended.

Yesterday, a chimney guy told me there’s gaps between tiles in the chimney, but that’s not likely related to our issue. He also doesn’t think grout is the issue/that we need repointing.

And finally… yesterday, I found no moisture on the ceiling. It was about as hot as usual, but this house is in the hills and can often get a lot of dew in the morning (the roofer said it can have “rainforest” weather in the morning). So what I’m saying is that I’m not sure if it was an off day in terms of moisture, or if one of the things that happened in the preceding days meant that moisture was reduced.

Thoughts? Ideas? Thank you for reading.


  • Larry Weingarten
    Larry Weingarten Member Posts: 3,388
    Hi, You have a lot going on! Finding the real problems is going to require some onsite sleuthing. You want someone who understands “building science”. I know such a person in the Los Angeles area and would be happy to share her contact info if you PM me.

    Yours, Larry
  • Big Ed_4
    Big Ed_4 Member Posts: 2,828
    More than one has the water staining , Lack of duct insulation or bad roof seal . Vulcanized roof ? The roofer makes the call . Normally they ask for the roof flange in place and they set and seal . The last photo with the rusty round duct has my curiosity , Are the outside ducts water sealed ? I know the South West is dry but it does rain now and then ...

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