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How far do sistered floor joists have to extend passed damage?


Sogeki's Avatar
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Join Date: Jan 2015
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TX

03-20-18, 09:55 AM   #1  
How far do sistered floor joists have to extend passed damage?

A family member moved a trailer onto our property and we're repairing some water damage. Water was able to get behind the siding or soak up through the bottom edge which lead to damage of the last ~6" of the floor joists over a 10' section of the header joist running parallel with the exterior wall that they tie into. The header joist is gone and will be replaced, but we cannot replace the floor joists or sister them full length because of ductwork and water and electrical lines running perpendicular through the floor joists.

It's a mobile home, 16' wide with full length 2x8 joists at 16" spacing set on 2 steel I-beams (also the trailer used to transport it.)
8' span between the I-beams with the remaining 4' on each side just hanging.

I can only get the sister joist to the first I-beam which is 3.5' of contact with the original joist. Will enough nails over that length be able to support the exterior wall or do I need to add another beam?

 
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marksr's Avatar
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TN

03-20-18, 01:08 PM   #2  
If I understand correctly that you only have the last 6" of the joist that is damaged, then your 3.5' of sistered joist will be plenty good.


retired painter/contractor avid DIYer

 
Sogeki's Avatar
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Posts: 34
TX

03-20-18, 08:23 PM   #3  
Okay, thanks.

Yes, the last 6" of the joists are gone along with the rim/header joist from what actually appears to be fire damage instead of just water damage.

I was thinking that the sister joists may need to be supported on both ends in order to reliably substitute a singular unbroken joist, so I was worried about the weight of the roof, ceiling, and wall overburdening the fasteners and allowing the short sister joists to pivot with the I-beam as a fulcrum because the new sister joists don't run far enough passed the I-beam to allow the building itself to hold down the other end.

Anyway, I've got it installed and it seems sturdy enough.

Thanks, again.

 
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03-21-18, 02:41 AM   #4  
The sistered joist is supported by the original joist provided the new is secured to it well.


retired painter/contractor avid DIYer

 
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