R502.6.1 Floor Systems

[4thorns]

"Joists framing from opposite sides over a bearing support shall lap a minimum of 3 inches........

Does this portion of the code mean that all 3 inches of the lap need to be over the support?

 

[Robert Ellenberg]

I wouldn't think so since a joist can sit on a 1.5" (2x2) ledger.

 

[TimNY]

In the case of a multiple-ply girder, the joist must only bear of 1.5"; it can bear solely on the outside member. A joist from the opposite side could extend 1.5" past the girder to provide the minimum 3" lap.

I see no issue with where the lap is as long as each joist has a minimum bearing of 1.5" on the girder. Otherwise it would say "shall lap a minimum of 3 inches over a bearing support".

 

[Jobsaver]

Robert and Tim have it right. Each Joist requires only 1.5" bearing. I think the 3" lap requirement is for lateral support to prevent the joists from twisting.

 

[4thorns]

Thanks for the replies.

Can anyone point me to documentation as to the exact purpose of this 3" lap and/or the splice blocking that this code says is acceptable.

 

[mark handler]

"R502.6.1 Floor systems. Joists framing from opposite sides over a bearing support shall lap a minimum of 3 inches and shall be nailed together with a minimum three 10d face nails. A wood or metal splice with strength equal to or greater than that provided by the nailed lap is permitted."

The Lap is for nailing, not for bearing

 

[4thorns]

Hi Mark,

" A wood or metal splice with strength equal to or greater than that provided by the nailed lap is permitted."

The word "strength" indicates that the lap or splice is resisting force(s) of some sort. I'm just trying to understand what they are resisting.

 

[mark handler]

Hi Mark, The word "strength" indicates that the lap or splice is resisting force(s) of some sort. I'm just trying to understand what they are resisting.

What are you proposing? A metal Strap? A wood member "sistered" on to the joists? The shear value of a 10d common nail is about 110 lbs

It's leaving it open based on field conditions, you are overthinking this stuff.....

 

[TimNY]

It all depends on the installed conditions.

In the basement, they may be resisting lateral pressure from soil pushing against the foundation.

In the second floor ceiling they may be helping to resist outward thrust of the rafters.

Or, they may just be helping the end of the joists to resist rotation.

I agree with Mark, don't overthink the issue.

 

[4thorns]

I appreciate your patience and you've got to believe that I'm not trying to be a pain in the a$$. I never grew out of the "Why" phase and I believe that that is why I have been told a gazillion times that I think to much. I also believe that I've gained a ton of knowledge because of it. You guys have listed a few possible reasons for this particular piece of code and I agree with all of them. I think that any one of them, or a combination of any of them may be the purpose of it. Unfortunately, and I mean no offense to anyone, this reason hasn't been presented to me. I know that whoever the actual author of this simple piece of code is, had a purpose in mind. Unfortunately I haven't found him/her.

Just because I think that there is a pot of gold at the end of the rainbow doesn't make it so. I need proof.