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Old 05-01-2010, 11:46 PM   #1
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Floor joists


I recently replaced some of the floor joists in my 50 year old house because they were rotting away. All of the new beams consist of two 2x4's glued and screwed together (making a 4x4) and span approx 8 feet. My problem is that the building inspector wont sign off on the job untill I can prove that my repair meets the load requirements (her chart doesn't show a listing for 2x4's). Where can i find a chart with the load ratings for 2x4's?

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Old 05-02-2010, 06:26 AM   #2
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Hi and welcome to the forum.

What size were the old joists? I do not think 2x4s are rated for floor joists at all, though I could be wrong.
You may need to get the correct/matching size and sister them to existing to get passed.

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Old 05-02-2010, 06:31 AM   #3
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Floor joists


Please help me understand: Were the original floor joist some type of 4x4 sized construction? What is the spacing between the joist? I'm sure the building inspector is going by what he/she was taught to look for as far as floor joist in your area. It's just that I have never ran across floor joist(s) which were of a 4x4 type construction, and I've worked on homes built in the early 1920's. Fifty (50) year old homes around here have 2x8's on twenty-four inch (24") centers for floor joist. At least the ones I have been under the homes. A picture or a drawing of this type flooring support would be helpful here. IMO--a floor joist constructed of two (2) 2x4's so as to make a 4x4, and spanning approximately eight (8) feet, as you have stated, will tend to sag unless there are a lot of them spaced very close together. David
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Old 05-02-2010, 09:00 AM   #4
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You would need to see if a lumber yard or someone else can give you a span on what you used
And Inspector may require an Engineer stamp
Also, a 4x4 is 3.5x3.5", (2) 2x4's together is 3x3.5"

Why didn't you use 2x6's?
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Old 05-02-2010, 09:12 AM   #5
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Floor joists


Quote:
Originally Posted by moondog View Post
I recently replaced some of the floor joists in my 50 year old house because they were rotting away. All of the new beams consist of two 2x4's glued and screwed together (making a 4x4) and span approx 8 feet. My problem is that the building inspector wont sign off on the job untill I can prove that my repair meets the load requirements (her chart doesn't show a listing for 2x4's). Where can i find a chart with the load ratings for 2x4's?
Might work for a post but never a beam.

Whats above your 4x4 beam, from beam to roof?
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Old 05-02-2010, 02:52 PM   #6
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They will work, depending on the species and fiber-bending rating (1100, 1500?) a 3x4 (2-2x4 nailed) with 1100fb will span 8' and carry 40# per ft. 1500fb carries 53#.
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Old 05-02-2010, 06:17 PM   #7
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The old floor joists were of the same construction, 2-2x4 nailed together, I just replaced the old wood with new. I assume it was built like that to allow more headroom since they are located in a cellar with only 6 feet of clearance. Also that part of the house may have been an add on by the homeowner because the rest of the house has 2x8 floor joist. Most but not all of the joists are an 16" centers. Some of them had to be moved to allow for new plumbing.
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Old 05-02-2010, 06:25 PM   #8
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In that case, I'd be more inclined to use 4x4s to replace/repair rather than 2 2x4s.
And if that's what was there, I'm surprised the inspector had problems with it.....?
Maybe if you went to 12" OC with 4x4s she'd be happier?

weird....

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Old 05-02-2010, 07:15 PM   #9
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I never use tables, I use an Excel spreadsheet I wrote to compute load capacity. That way I can analyze any size beam. A pair of 2x4 could be 3.25" x 3.5", depending on the exact size of the 2x4. As previously noted by others, a pair of 2x4's is adequate for the span, assuming the lumber is relatively high grade. Unfortunately, you may need to get an engineer to sign off on this, since it is an unusual arrangement. Also, the code may have greater than 40psf requirement for the floor load, which would change the analysis.
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Old 05-03-2010, 12:11 PM   #10
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Floor joists


go to lumber saw mill and get some green oak 4x6 that will hold

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