# Shadowed Ceiling - from trusses??



## kevan (Apr 1, 2005)

We are a high volume home builder and I have a problem that we have not seen before.

A home owner that has lived in the house for 3 years now is seeing "shadows" of the trusses on the ceiling? There are dark lines in the cathedral ceiling that line up with the trusses?

I have seen similar shadowing from excessive soot in the air but this home owners never burns candles and even runs a media style air filter?

Can anyone shed some light on this?

Kevan


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## JMGP (Mar 29, 2005)

This is a tough one with out actually seeing it.

some ideas...

Were the joists wet/moist when the drywall was installed? Moisture might have finally made it's way through. The drywall will suck the moisture out of the wood. Im sure its not wet but it might of softend the ceiling paint a little and made it darker.

Is the home settling and put a little pressure on the ceiling were it might be bulging and you seeing shadows from it?

Looking at it from the floor gives a different perception than if you get a ladder and look at it real close. It might give you a better idea of what is going on. 

Just a thought, I might be way off.

It might just need a couple coats of premium paint. Use a primer sealer on the dark areas first.

Joe


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## Mike Finley (Apr 28, 2004)

I have seen a highly detailed and technical explanation of this on another site, but I can't remember where. I believe it all revolved around different temperatures between where the joist met the drywall and the insullation and some kind of moisture difference that collected dust and dirt over years...


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## Dale (Aug 26, 2004)

I remember reading that too..something to do with the cooler temps over the rafters or studs actually slowing down the molecules and the slower things move the more likely they are to "stick" and become visible over time. Someone brought up "Brownian Motion" or some complex explaination...can't quite remember.


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## Mike Finley (Apr 28, 2004)

http://forums.jlconline.com/forums/showthread.php?t=7758&highlight=dirt+joists


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## Rusty Nails (Apr 3, 2005)

Mike Finley said:


> I have seen a highly detailed and technical explanation of this on another site, but I can't remember where. I believe it all revolved around different temperatures between where the joist met the drywall and the insullation and some kind of moisture difference that collected dust and dirt over years...


I've seen this before and it had to do with 24" center trusses, and 1/2" drywall.

Is it 1/2" drywall?


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