What Caused these Drywall Seam Stains

I was positive these stains were from wet ceiling joists. Once I inspected the attic, I found they are trusses, and are perpendicular to these stains. Moisture readings in the ceiling were okay, humidity level inside was 60%. They are consistently spaced 4 feet apart from one end of house to other.

Any ideas what caused these stains? All I can think of is brown drywall compound showing through the white ceilings.

They do look “redone”-5 yr old house.

BTW, the hardwood floors pop and crack when walking on them, and there is lots of moisture and mold on the floor joists in the crawl.

I expect it is Ghosting and there is an open air space at the joists .

Wet joists would even make the Ghosting worse

Do a Google, or a NACHI search on Ghosting .

60% moisture is to high in my books Some remedial work needs to be done .

Could be damp Crawl space or basement . A good dehumidifier could be a huge improvement stop venting the crawl space if there is one

Thanks Roy. Stop venting the crawl space? Is that a typo?

No it is a** fact** I can give you many reasons .
read this and I will look for others Web site I have .


Okay, I read some “ghosting” articles, and makes perfect sense,** except** these stains are perpendicular to the joists. Maybe the drywall seam tape is collecting the “ghost dust”.

Thanks Roy. I read the article. Good stuff! :smiley:

I expect there is a 2*4 at the joint transferring the temp difference .
1/10° F of degree will attract the smoke ,Dust,
Do they burn candles ,incense or a wood stove all tend to help the ghosting.

More on Crawl spaces




It definitely has to do with the recessed drywall edge seams. At first look, I would have said the tape was bleeding through, but I don’t see this on the butt joints. Must be related to the compound type absorbing humidity and discoloring the mud. It’s not ghosting due to thermal bridging of the trusses.

Thanks, Brad. Those were my thoughts as well (after reading up on ghosting). I originally thought it was cold/moisture transfer from the trusses, but after going in the attic I discovered the trusses are perpendicular to the stains.

The house has been vacant for 5 or 6 months, and there is a wood burning fireplace in the great room. There is also no exhaust fan in the kitchen. The insulation is blown in, and was just installed when the buyer moved out to sell the house. I’m assuming there was no insulation until then, since there is nothing under the blown in.

I agree. Its unlikely to be ghosting.

It is odd and I wonder why it only appears at the tape joint and not where the sheets butt up to each other at the ends.

I suspect a coat of drywall primer was not used so some bleeding is occurring and the tape joints.


It could be a bag product mixed with dirty water. It’s a little different than general purpose drywall compound. It also looks like the long seams were not filled completely and may show a little shadowing…I see that a lot too. Who knows?

Correct. These dark stripes are not on the butt joints, but go the length of the house in every room.

I’ve used joint compound that was “brownish” in color, but it always covered well by the primer. I saw a few empty gallon bucket of Kilz in the laundry area. I think the sellers were trying to cover those seams or something.

I think now the big issue for my buyer is the massive mold/moisture in the crawl and only 20 lbs of water pressure. Seller says it’s municipal water, but it has what appears to be a well pump and bladder tank in the crawl space.

It’s what happens when you mud in some of the joints with PL400. :mrgreen::mrgreen:

I was going to say it may have been cracked so someone decided to repair the seams

That’s what it looks like to me. The strips that are showing are too narrow to be the original joint compound installed during the installation process. Repairs may have been done with something that is bleeding through the cheap water based paint. Someone may have walked around in the attic and caused cracking at the joints. The horizontal section of a truss cannot bear much load where there is no support connections in the system. Using water base Kilz stain blocker as a primer will bleed through cheap water base ceiling paints. Some times people apply Kilz over the areas they caulked (because they did not want to re-tape all the cracks). Then it bleeds through the cheap paint that goes over the Kilz.

That makes pretty good sense, and close to what I verbally told my client after emailing the report. All the causes are mere speculation at this point. The report just notes the cosmetic defect observed, once moisture was ruled out as the cause.

Thanks everyone for your valuable input. This is what makes InterNACHI great! :smiley: