Ask Me Help Desk - Roof Rafter Cracked

I recently heard a few loud bangs from the attic. I checked and found that several rafters have cracked. The house is 19 years old, stick built with a gable roof at 6/12 pitch. The rafters are 2"X10" (no trusses) so I can't imagine any pressure that could cause this to such a solid roof. There hasn't been any large amounts of snow. The roof is not sagging and the cracking is minor.

Can anyone speculate on why this is cracking and provide some help with fixing it? I am considring glueing/nailing a sister rafter next to each bad one and putting in some collar ties. There are only a few collar ties in the roof... about every fifth rafter. Should each have a collar tie?

Yes that is EXACTLY why the rafter cracked. Every rafter Has to have a collar tie. Sister up the cracked rafters and out in collar ties. WOW as a builder I never head this before.

Now before you just throw in sister rafters it would be wise to get each sagging rafter roof pressure off on the that rafter. You aren't going to really straighten out the downward curve of the old rafter but some upward pressure to be applied to de stress it. Before you put in the sister tie look at the curve on it of the 1 1/2 side. Put the curve/camber towards the roof sheeted side, This will greatly improve its ability to carry a load by opposite deflection. You don't have to glue it to the sister rafter. Just side nail it about every or 16 inches to the old rafter. The most important part here is a good nailing on the Ridge beam and a good seat on the outside plate. And again a collar beam/board on each rafter. Those you might want to double up on both sides of single rafter/new double rafter on each side of the peak

Signed 21 Boat

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Please describe the crack, does it reach one end of the rafter and show like two separate boards?

Quote:

Originally Posted by ballengerb1

Please describe the crack, does it reach one end of the rafter and show like two separate boards??

The cracks are very thin and seem to run the entire length of the rafter from the point they're nailed into the ridge. I've looked at several neighbors houses who were built by the same framer in the same design and none are having any trouble. I get the feeling the collar ties should have been put in place. Thanks for any help you can provide. Was it o erkill to use 2X10 rafters? I have a vaulted ceiling in part of the house which required 2X10's by code. When the lumber order came they delivered all 2X10's so we decided to just use them for the entire house. The other concern is why this is happening after 19 years?