Trusses deflecting or something else?

[kmart30]

Anyone see something similar to this? It looks like the trusses are starting to telegraph/deflect in the drywall ceiling and it is noticeable. There isn't any major signs of cracking but this is a brand new house and could get worse overtime with creep. Its more visible depending on the amount of light in the room but regardless of how visible it is its still there. The trusses are running in the same direction and spacing as shown in the ceiling. Anyone see this before and do you think this could be an issue?

 

[jayrod12]

Looks like sub standard taping. Did they use 1/2" or 5/8" drywall?

 

[TehMightyEngineer]

I wouldn't think taping is the issue as they should only be taping the drywall seams.

I just want to confirm that this is actually a deflection? I ask because sometimes you can get thermal bridging causing colder spots allowing slightly more moisture to gather on some spots which trap dust and dirt causing thermal tracking:

http://www.diychatroom.com/attachme...ng-why-there-dirt-everywhere-ceiling.ex.1.jpg

Ian Riley, PE, SE
Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

https://www.facebook.com/AmericanConcrete/

 

[kmart30]

1/2" drywall. Seams are not that closely spaced. This is not thermal related "ghosting". Although small there is deflection. It seems to be worse near mid span. One side is bearing on a plate and the other side is on hangers attached to a ledger.

 

[TehMightyEngineer]

Hmmmm, I still would think that joist deflection would just bring the whole drywall layer downward; not just locally at the joist.

I'd guess something thermally or moisture related, causing warping of the drywall. Never seen this before though so it's only a guess.

Ian Riley, PE, SE
Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

https://www.facebook.com/AmericanConcrete/

 

[SwinnyGG]

Drywall is flexible. If all the joists moved, the ceiling would move. There's nothing keeping the drywall in place between the joists.

This looks to me to be a moisture effect, or the result of a lot of insulation piled on top of thin drywall.

 

[jayrod12]

And 1/2" drywall should never be put on ceilings. 5/8" minimum. If they went and put 24" of blown-in insulation up there you could be getting some sagging of the drywall between the trusses.

 

[kmart30]

Builders do the min. Requirements and 1/2" is allowed unless it's in the garage under a habitable room for fire rating.

Moisture from the trusses? I know trusses can sit on site for a good time in the elements until they are installed. There would probably be a 2 month time period from when the roof is dried in to hanging of the drywall. If it was moisture wouldn't it be more consistent along the span and not more worse near mid span?

 

[jayrod12]

Did you stick a straight edge across the lines? From the picture it certainly looks like the drywall is sagging between the trusses, but perhaps it's just my eyes playing tricks. If the drywall is sagging then it has nothing to do with the truss deflection.

 

[CANPRO]

Agree with others that this is not a truss issue. The bump in the ceiling appears to be about the same for all of the trusses, so if all of the trusses moved the same amount then you wouldn't see local bumps at the trusses, you would see a global "bow" in the finished ceiling. If this defect occurred at a single truss, I would be investigating that single truss for some kind of failure.

 

[BridgeSmith]

Is it sagging between the joists or is there a hump protruding down at the joists?

 

[JoshPlumSE]

jgKRI makes the most salient point. And, he's not even structural!

If the trusses were all deflecting similarly, the drywall would just move with them. Therefore, it really can't be a truss issue.

 

[MotorCity]

Perhaps moisture made the drywall more pliable. Is the space above the ceiling a habited area or an attic space? If its an attic space, the roof may not be properly vented. Also may want to check for mold.

 

[kmart30]

There is attic space above it with blown in insulation. I will put a level across a few spans and see what it shows. I think an infrared flir will show if there are any moisture issues.

 

[msquared48]

To me, it looks like the drywall is swollen at the truss locations, and to me, that implys the trusses were moist when the sheet rock was applied.


Mike McCann, PE, SE (WA)

 

[BridgeSmith]

"To me, it looks like the drywall is swollen at the truss locations..."

That's what it looked like to me as well, but others seemed to indicate they thought it was sagging between the joists, so I thought my eyes were deceiving me.

"...to me, that implys the trusses were moist when the sheet rock was applied."

Very possible. My initial thought was they left a hump of joint compound along the entire line of screws, which would be either the result of a lousy job of screwing, where the heads were left sticking out, or just crappy mud work.

 

[msquared48]

Yes, but this ceiling has a knockdown finish that should hide taping and mud/sanding imperfections.

Moreover, the mud work would not be at every truss location along the entire length of the trusses. No, this is not bad mudwork.

Hopefully they used minimum of 4x8 sheets with the long direction placed transverse to the trusses...


Mike McCann, PE, SE (WA)

 

[BridgeSmith]

"...the mud work would not be at every truss location along the entire length of the trusses."

Well, there definitely shouldn't be mud all the way along the trusses, but if someone was very sloppy in mudding the screw holes, or the screws were not countersunk properly and required mudding over, it could end up looking like that.

The bottom line in regards to the OP, is this is not a structural issue with the trusses. At worst, the drywall is in danger of falling down and there could be a mold problem above.

At best, it's just a poor texturing job where the guy overlapped his passes when he sprayed it.

 

[Jerehmy]

Are there moisture issues in the attic space? It is possible that seasonal moisture fluctuations in the attic space due to improper/lack of ventilation are causing moisture content fluctuations in the wood. Doesn't look like deflection to me. I've seen this once before, but it was on an old plaster ceiling finish throughout the house.

Can you do some selective demolition? Cut out a 4" x 4" section at one of the "ridges". Bring some tools, mud and tape before you go.

 

[hokie66]

Why the textured finish? Probably to hide the irregular surface? I think a textured finish in a "brand new house" indicates intention to hide faulty work.