Replies

1. 
   JTC1 | Sep 11, 2009 10:06pm | #1

   I don't think there is a maximum -- could ovelap full length if you wanted, AKA, doubled.

   Somewhat self regulating -- builders would not be inclined to "waste" lumber, but might be inclined to skimp - hence a minimum is stated in the code.

   Code specs minimum not maximum building standards --- if you wanted to use 2x12 joists where the code only requires 2x8 -- the inspector / code writers do not mind.  Have never heard of an inspector writing up a job because of "floor joists underspanned -- must replace with smaller".

   No authoritative source, just my feeling / guess...... 

   Jim

   Never underestimate the value of a sharp pencil or good light.
2. 
   calvin | Sep 12, 2009 12:01am | #2

   I know of no code reference, but have come to find out that oftentimes it is just enough to aggravate the drywaller.

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3. 
   Framer | Sep 12, 2009 01:07am | #3

   Jon,

   What's concern? Is it that you have a situation where they will overlap and you don't want to cut them? I never overlap more than 10-12" because the end of the could possibly stick up or down next to the other joist. I do think the is something in there about no more than 12" though.

    

   Joe Carola
1. 
   jonblakemore | Sep 12, 2009 06:01am | #5

   I don't want them to "scissor" and create a hump, as you noted.The situation today was a 19" overlap, which is less than the allowable cantilever for a 2x8 joists.Do you happen to know the code section about the 12" limit? If it's there, I was looking in the wrong place. 

   Jon Blakemore RappahannockINC.com Fredericksburg, VA

4. 
   rlrefalo | Sep 12, 2009 01:39am | #4

   The reason you want to keep the lap to a minimum is that the tail end will rise as the joist sags over time, causing a hump in the floor.

    Rich

1. 
   jonblakemore | Sep 12, 2009 06:02am | #6

   That is the reason I'm concerned with, but what's your max allowable length? I can't imagine 1" being a problem, so some is okay. But what is too much? 

   Jon Blakemore RappahannockINC.com Fredericksburg, VA

1. 
   jimAKAblue | Sep 12, 2009 08:20pm | #7

   At some point in my career, I was told that the maximum was the depth of the joist.

   I always specified half the height of the joist, if possible.

   One problem that can occur with joists overlapped too much is the teeter totter effect. A joist cantilevered 19" as you have indicated will actually move up and down as the floor is walked on in the midspan of the main joist. That small up and down action will work fasteners out and cause squeaks. That nuisance could be mitigated to some degree if the cantilvered joist is securely nailed within 1" of it's ends. To me, that would be wasted nailing. I simply preferred that we lapped everything a minimum amount, therefore requiring only a couple nails at the lap. Normally, there's no reason, or benefit,  to double the amount of nailing at this joint.

5. 
   AitchKay | Sep 12, 2009 11:35pm | #8

   I think it's the depth of the joist, too.

   Some extra-cautious builders taper the loose ends starting at the bearing point. Not a bad idea.

   AitchKay

1. 
   jimAKAblue | Sep 13, 2009 05:34am | #9

   I've considered that but if you don't nail them securely and allow them to cant and flex, then they can rub and squeak.

1. 
   frammer52 | Sep 13, 2009 07:11pm | #10

   We always used the 1' rule.  No more than!

   BI told us to use, never failed an inspection over that!!