roof sagging

[T Buckus]

How do you fix a sagging roof? It’s a cut and stacked roof with tih rafters spanning at least 20′. The previous owner put in a support wall, but didn’t jack it up. I have to replace the shingles anyway so can I just nail new 2×6 to the original rafters and resheat the roof? this happened to only one side of the house. Any experienced info would be appreciated.

[Paul C.]

This is a pretty serious job you are considering, and
there is alot to consider. After you remove the
existing shingles and sheathing do your old rafters
spring back? If so you are off to a good start.
Just nailing a 2×6 to the existing rafter would only
add weight without much structrual strength. The
rafter jacks are critical there. Consult an engineer
or architect to examine your existing roof to determine
how to best repair it without adding too much weight. Then again removing the old shingles may be
the answer.

[Bruce M]

Hi T:
The solution to your problem depends on several things: The size of your current sagging rafters; how they are attached at the ridge; how far apart they are (on-center spacing); the type and grade of wood and the pitch of the roof. Sistering on dimension lumber (2X6 is probably not enough) is a possibility, as is simply replacing the rafters one at a time. Trust me, if you remove the roofing materials, the bowed rafters will not spring back. Right now, they are in tension (as opposed to compression when they were new), and it will take a long time of applying static lift to straighten them, so jacking up the rafter is of no value.

I agree with Paul, if you don’t have a good confortable feeling about taking this on, getting a residential structural engineer in at this point would probably be your best bet. If you’re going to go through the trouble and expense of fixing this porblem, might as well do it right the first time 🙂

Best wishes

Bruce M

[Author]

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