Cost Estimate - Sunken rafters under the roof (showing dips in the roof)

Posted by on November 30, 2006, 5:43 pm

Hi,

How much does it cost to fix sunken rafters under the roof? The sunken
rafters are causing dips in the roof.

What is the average cost "per rafter" ?? Are these a common problem?
Is it vital to fix them asap?

Posted by marson on November 30, 2006, 6:10 pm

wangchieh@wongfaye.com wrote:

> Hi,
> How much does it cost to fix sunken rafters under the roof? The sunken
> rafters are causing dips in the roof.
> What is the average cost "per rafter" ?? Are these a common problem?
> Is it vital to fix them asap?

absolutely impossible to even guess without a lot more info. this is a
remodelling problem that really needs an experienced carpenter to crawl
in the attic or whatever and take a peek.

Posted by Wiley on November 30, 2006, 8:27 pm

wangchieh@wongfaye.com wrote:

Are you sure its the rafters ?

Truss roofs are placed on 24 inch centers, with usually 1/2 inch
sheathing that should have ply clips between the trusses.

Framed roofs have 2X6 through 2X12 rafters usually placed on 16 inch
centers, and are much less likely to have any dips.

Go up in the attic and check, you may have broken trusses or the roof
may be rotten in places.

But a lot of truss roofs have sags between the trusses.

Posted by on December 2, 2006, 10:28 am

Hi,

Dips in the roof are caused by a number of ailments all related to each
other. First you'll need a ball of string or a chaulk line. String
the bottom of the ridge to check it for sag. Next, string across the
bottom of the rafters from gable to gable at their midpoints to check
for sag.
Post under the ridge to make it as close to straight as possible,
without causing damage to ceilings or walls(taking into consideration
that too much movement will result in cracks in your plaster).
Cut 2x4's to a length 1/2 inch longer than the height from joist to
rafter at mid-rafter span. Use these to wedge each rafter up by
footing on joist and bending it under the rafter. Rafters will
straighten when these temps are posted under the rafter. Do this for
each rafter pair(front & back make one pair) and check across gable to
gable for staightness.
After a rafter is straight, with the temp still in place, you'll need
to install collar ties at 1/3 the height down of rafter to joist
measurement.
As you can see, this is quite involved and more likely a job for an
experienced framer. Not just any woodworker.

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