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Old 02-06-2010, 08:53 AM   #1
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Enlarge Joist Spacing


Is it within code to enlarge the space between floor joists? Not something I'll do, just asking.

I have two 12" air return ducts that are squeezed between two floor joists. This is distorting the ducts and restricting return air flow.

Can a section of joist be attached to the outside of the existing joists to bridge either side of the ducts? Could a 15" section of the existing joist then be cut out which would then provide a 15" opening for the 12" ducts.

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Old 02-06-2010, 10:11 AM   #2
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Enlarge Joist Spacing


It depends upon the joists, how the floor was built/supported & what they are supporting (load)

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Old 02-06-2010, 10:35 AM   #3
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Enlarge Joist Spacing


Quote:
Originally Posted by Earnie View Post
Is it within code to enlarge the space between floor joists? Not something I'll do, just asking.
Simple answer: No, you would need to re-frame the opening.
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Old 02-06-2010, 01:27 PM   #4
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Enlarge Joist Spacing


Quote:
Originally Posted by AtlanticWBConst. View Post
Simple answer: No, you would need to re-frame the opening.
I think he's talking about something like this
http://www.chambers-house-build-it.c...eningnails.jpg
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Old 02-06-2010, 05:52 PM   #5
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Enlarge Joist Spacing


Yes, just as the drawing shows but I would only need to modify one joist bay. I'm sure this will require a building permit so the County will need to approve.

Thank you.
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Old 02-06-2010, 06:28 PM   #6
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Enlarge Joist Spacing


As Atlantic correctly said, just re-frame the opening.

Most heat supply register/returns are in a wall, so meet the within 3' rule per code:

"Section R502.10 Framing of openings in floor framing.
Openings in floor framing shall be framed with a header and trimmer joists. When the
header joist span does not exceed 4 feet (1219 mm), the header joist may be a single
member the same size as the floor joist.
Single trimmer joists may be used to carry a single header joist that is located within 3
feet (914 mm) of the trimmer joist bearing. When the header joist span exceeds 4 feet
(1219 mm), the trimmer joists and the header joist shall be doubled and of sufficient
cross section to support the floor joists framing into the header. Approved hangers
shall be used for the header joist to trimmer joist connections when the header joist
span exceeds 6 feet (1829 mm). Tail joists over 12 feet (3658 mm) long shall be
supported at the header by framing anchors or on ledger strips not less than 2 inches
by 2 inches (51 mm by 51 mm)."

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Old 02-06-2010, 07:15 PM   #7
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Enlarge Joist Spacing


Thanks for the reference. Made a note on that section of the code.

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