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Old 07-05-2005, 11:59 PM   #5
Da Home Builder
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Join Date: Jul 2001
Location: Boerne, Texas
Posts: 85,906
Two kinds of deflection to consider here, Jon: Joist deflection, and subfloor deflection. The sistering of the joists stiffens that part. It can also aid in reducing the spacing between joists if the sisters also support the subflooring, but that's not a necessity. The subflooring can be augmented separately if necessary.

When you install a sister that is not as deep as the existing (2x6 sister on 2x8 joist, for example), the optimum location of the sister for maximum stiffening is at the bottom of the existing joist and well attached to it. That means it doesn't touch the subfloor, but that ain't what we're fixin' with the sisterin'.

Attaching the sister the full length of the existing joist is the most effective method, but you can do a great deal of stiffening if you can sister at least two thirds of the center of the joist. I prefer all sistering be done with wood glue and screws if at all possible, and it looks possible with what you've got. You can do it with construction adhesive, but not as well in most cases.

Like Mark, I'd remove the wires where necessary and re-do'em after. Some of'em you might find enough slack to make only one splice, looks like.

Oh, and just by the color, if my monitor don't lie too much, I'd say that's Doug Fir, but not a real good grade. Unless it's Cedar.

My opinion; worth price charged.

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