strapping crack in joist


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Old 08-25-14, 07:01 AM
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strapping crack in joist

Hi All,

I've removed some insulation from a flat roof to get it ready for spray foaming. I've been walking on the roof above to repair leaks to another part of the roof and noticed a creaking when i walked on the flat roof.

I've noticed this worrying crack in one of the joists, coming out of a knob and tube hole. This joist has a large 3x3" chunk taken out of it 3' down from this crack. I suspect the weakened joist (both of these holes) couldn't take my weight? The house is 1950s era.

I know this joist should be replaced but i'm just wanting to patch it up to get through the next 5 yrs. There's many things wrong with this house and i'm saving them up for a big reno job.

I want to repair this joist by first applying upwards pressure to restore it to its original position (crack closed) by using a 2x4" and a wedge. Then i would place a large enough piece to cover the crack, around 3' on either side of the crack and drill and screw them in. Perhaps i would also put lag bolts from underside of the crack. I know this isn't perfect but i assume better than doing nothing.

Can anyone comment on whether this is a bad idea, will i make situations worse? Is there better method to strap it?

cheers
oman
 
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Old 08-25-14, 07:38 AM
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Nope, not a bad idea at all. It's called sistering and if you search the web you'll find guidelines and instructions but it sounds like you've already got a good plan. Since you've got good access I would sister as much of the joist as possible including the notched area.

Is the knob and tube wiring still active or being used? If not I like to remove the old wiring so it does not lead to confusion in the future. When you go to sell the house you don't want an inspector thinking you've got knob and tube wiring when you don't.
 
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Old 08-25-14, 11:39 AM
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Thanks for that Pilot Dane,

A guy at work mentioned the same terminology, sistering, so i'll follow the instructions i find. I'm also planing to remove the knob and tube. it's disconnected and on the to do list

oman
 
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Old 08-25-14, 11:48 AM
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Construction adhesive and deck screws will do just fine. I'm surprised you don't have an issue where that galvanized pipe/flue runs. Thats way too much notched out I think.
 
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Old 08-26-14, 03:00 PM
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I'd suggest you don't install lag bolts coming up from the bottom, mainly because of the large knot being present could result in the lags splitting the joist open, completely, at which point you'll have a nice chunk of firewood (after removal and replacement of the joist).

You didn't say what material you're going to sister with. I'd suggest using a 2 x 6, at least 4' long. Glued and screwed, it would provide enough meat to carry the joist's loads. As long as big, fat guys don't go marching around on the roof, of course.
 
 

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