What is causing my roof to droop?

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As you can see from the picture, the roof over my carport is sagging. Many of the houses in my neighborhood (most built in the 50's) are the same way. What causes this and do you think its a problem or just cosmetic? I was up on the roof putting up Christmas lights a week ago and it did NOT feel soft or bouncy walking on it.

 
Are you able to get into that attic section of the roof to see the structure? Could.be joists shifting or plywood getting soft. Or is the sheathing thsoe strips of wood that they used to use a long time ago?
 
Originally Posted By: JC1
Are you able to get into that attic section of the roof to see the structure? Could.be joists shifting or plywood getting soft. Or is the sheathing thsoe strips of wood that they used to use a long time ago?


I agree, no way of knowing unless somebody is looking what is going on underneath.
May be the underlayment board broke or the supporting wood broke.

They are not designed to last for 60 years.
 
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Built in the 50's, I'm going to guess that it is conventional rafter design (vs. trusses). That it is happening only over the car port is your first good clue. I would look at the front and back fascia areas to see if they look pushed out a tiny bit, allowing the ridge to sag. My guess is that they continued the same roof design over the car port that they used on the rest of the house. But, the car port has almost nothing (no front/side/center bearing walls) supporting and holding the rafter system together as the "locked together" unit it is designed to be. Or, maybe that HUGE joist span over the car port is just too long. Look for sagging joists too, which would allow the ridge to sag.

An inspection by a trustworthy builder would reveal the root cause. Since you have no snow load in Florida, and if their are no major structural deficiencies (i.e., cracked ridge board, etc.), it might be just a cosmetic thing. There are sagging roofs that have lasted for centuries.
 
I don't like all that weight only supported by two steel poles.

A roofer has a better idea and knowledge of why your roof is lower.
 
Where are your roof vents?
Also, how much insulation is under that roof and is any insulation-roll attached directly to the inside of the roof - between the beams?
 
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Best would be to get a structural engineer. They might be $80 per hour and he should be able to examine the roof and write a report in 2-3 hours. But he will need to get into the attic area to look.

Roof trusses are engineered and so they should not be a problem assuming no insect or water damage. I spent my college summers building way too many roof trusses, using massive machines to press the plates into the wood.
 
Not enough of a collar tie on the rafters. Looks easy to fix though. Put a couple of A shores up under the fascia to carry rafters and ceiling joists put a couple A shores at half span of the ceiling Jack up shores an inch above where they were. Install collar ties or a W tying a rafter to to a ceiling joist.
 
As suggested already, you or someone needs to get up into the attic. There are a lot of causes for a sagging roof and since you are in Florida the first thing I thought of was termites. A visual inspection is needed.

Also check your storage room too. Does the door open smoothly? Any signs of settling?
 
You can start with a roofer-then a structural engineer-if needed.
 
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The steel poles are good for like 10,000 each as long as kept "in column". The sag is not effective collar ties.

Jack up the center +1" in the middle. Install some 2x6 collar ties from rafter to rafter and let it settle. Use modern self tapping screws and some good PL8X on the faces to be joined. Should come out pretty straight
smile.gif
 
That's very common in the northeast and that's usually from the snow on the roof. Had that happen to lots of houses after we had 100 inches of snow one year. As others said, there's some weakness somewhere. Maybe your walking around weakened it or you have two layers or more of shingles. But it could be trusses or termites. I wouldn't bother with a structural engineer. In the northeast, most home inspectors just said that it was a cosmetic issue as we don't normally get 100 inches of snow every year.
 
It's possible it is poor ventilation, and over the years dampness could be causing the plywood to warp. Is it insulated? If so was the insulation job done properly? It's hard to tell from pictures, if I saw it I'd know. You might want to investigate a ridge vent [if possible], or some other way of venting it.
 
Originally Posted By: BrocLuno
The steel poles are good for like 10,000 each as long as kept "in column". The sag is not effective collar ties.

Jack up the center +1" in the middle. Install some 2x6 collar ties from rafter to rafter and let it settle. Use modern self tapping screws and some good PL8X on the faces to be joined. Should come out pretty straight
smile.gif



This is what I did at my camp … another reason is the differential pressure of storm force winds (coastal) … the ties give it more separation force resistance …
 
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