Floor joists and sill plate rotted


Old 03-12-10, 12:11 PM
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Floor joists and sill plate rotted

The portion of house with problems is a cantilevered two story section. It's 20X30 ft with 2x12 floor joists spanning 20ft. The 2nd story is also 20x30ft but hangs over the front of the house about 4ft and in turn provides 4ft of balcony in the back that allows access via an exterior stairway to the second floor. The first floor is one large room with no other walls on the interior.

The floor joists that support the front section are completely rotted, causing the entire front of the structure all 30ft to sag. I assume from seeing the severity of the rot that the majority of the front wall at a minimum is also rotted. The first floor is constructed of block and is level and very solid. House is around 50 to 60 years old.

Seeing as how the first floor is one open room, I can rip the entire ceiling out to access the joists above. Can I sister the joists without spanning the entire 20 ft? I foresee having to sister or reinforce all the joists that make up the cantilevered portion. How would YOU do it?

Thanks for any and all help, Damon

Last edited by 85diesel; 03-12-10 at 12:12 PM. Reason: new info
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Old 03-13-10, 09:16 AM
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After you remove the ceiling, you have to build a temporary wall perpendicular to the joists, about 6 feet from the rot. Build it in such a way that you can use jacks to take the pressure off the sill plate.

I don't see how you can avoid having the new joists the entire length of the room unless you build permanent header in the middle of the room. You can always box it when you redo the ceiling.
Old 03-19-10, 08:46 PM
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You might be able to to sister onto the joists. You have to look to the local code for " back span to cantilever ratio"

It will probably be 2:1 or 3:1 in which case you would only have to go back 8 to 12 feet. Don't forget to put the blocking and or "cats" at the bearing points.

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