Joist stiffening (Notches)

Old 09-18-04, 09:24 AM
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Joist stiffening (Notches)

I need to notch (3x10) a 2x8 joist to run a vent for a range hood. My original plan was to have a 4' x 1/4" steel L shaped plate made to wrap around the bottom of the joist with 8 bolt holes. But it was suggested that I bolt and glue 1" plywood to each side of the notched joist, as the steel would put pressure on the wood only at the bolt holes. Although I thought the wrap around (1.5") would help to support the bottom of the joist.

Does anyone know the span rating for this type of 'engineered' joist. In other words how much can a 2x4 plywood sandwhich support in addition to the remaining 2x4 section of joist.

Any other solutions also appreciated.

BTW. Span is 12' and the notch is roughly 4' from the end of the joist.
Old 09-19-04, 12:56 PM
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Notching joists

NOTCHING JOISTS: Not more than 1/4 the depth at ends, not more than 1/6 the depth in the top and bottom of joist.


BORED HOLES IN JOISTS: Holes shall not be within 2 of the top or bottom of a joist, the diameter of any hole shall not exceed 1/3 of the depth of the joist.

Check with your local Building Inspector regarding Codes in your area.
Old 09-22-04, 11:33 PM
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Why would you weaken the structure instead of relocating the vent.
There are available for virtually any style of venting material, turns, elbows, transitions from rectangle to round.
Old 09-23-04, 07:40 PM
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As suggested, any notching on this 2x8 is asking for trouble. rethink your situation over carefully and I bet you'll have better alternatives for the venting.

I frown on notching a 2x12 let alone a 2x8 and that is dimensional lumber but if you need to modify anything, let it be ductwork or relocating the range. Once a structure is built, cutting without adequate support is not a good idea. Can you build a small soffit?

Engineered joists - I-Joists are another issue. Please read the following, (See page 17)

Hope this helps!

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