Ceiling discoloration from joists?

During a inspection today I noticed some discoloration on the ceiling. The discoloration appears to be from the ceiling joists above and run perfectly straight and are evenly spaced (just like joists would be). The ceiling is white and the discoloration is a light tan. I was not able to get a good photo but would like any of your ideas on what this might be?

Stains (ghosting) caused by thermal bridging.

go here and read all about it…good stuff.

Yes, good info:



This is great info and explains in detail.
Thanks so much.


Hey Don,

The Brownian Motion article explains the process well. Interestingly, in the last home which I inspected where thermal bridging was evident on the ceiling, there were not, nor have there ever been smokers in the 30 year old home. There was however, ZERO ventilation in the attic… and I mean zero. It was a large, two story executive home with NO roof vents and NO soffit venting.

Bear in mind that thermal bridging can be a symptom of a deeper problem. My attic inspection explained the cause of the bridging. No ventilation equals excessivily high heat in the summer and excessive cold (and I suspect freezing) in the winter - with these extemes being transferred through the denser ceiling joists.

I have had pretty good luck photographing thermal bridging. I find the area in the room where my eyes can “see” the bridging marks the best, then take a couple photos from this eye-level spot - one photo with flash and one without. One of them usually does the trick.

Good luck with it.