Wood member end bearing requirements

[shaneelliss]

I have heard a few building officials say that all wood members (beams, joists) must be bearing on at least 1.5" at the support. I cannot find this is the code and wondered if anyone else knows where it comes from. I think it is probably good practice in most cases to have the beam or joist bear on something rather that have it nailed in, but is it required? Is it acceptable to use something like a simpson A35 bracket instead of a hanger with a bucket?

 

[woodman88]

Per the 2009 IBC Section 2304.4 "The framing of wood-joist floors and wood framed roofs shall be in accordance with the provisions specified in Section 2308 unless a specific design is furnished."
So if you have a design by an engineer (or building designer, where allowed by code) the design controls the bearing requirements. As long as the design does meet the code and engineering standards requirements.
The 2009 IBC Section 2308 does state a minimum required size of 1.5" (or a 1x4 ribbon and joist nailed to studs) in Section 2308.8.1 for floor joists. Headers 1.5" requirement is in Section 2308.9.5.2. The 1.5" minimum bearing is also noted as require in many other sections of 2308.
Also where wood is bearing on concrete or masonry 3" minimum bearing is stated the Section 2308.7, 2308.8.1, etc.
The same applies to the IRC.

As for your detail, it would depends on what forces need to be transfered. But I would prefer to use a hanger and see no real reason not to.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[MiketheEngineer]

While 1.5'' may work engineering wise - construction practices often don't match up. I tend to like 3'' minimum unless inspected and checked.

 

[shaneelliss]

Thanks for the responses. I have never carefully read through section 2308 because in my mind it was just for non-engineered design. But there seems to be some good design practice points in there.

I recently did a design for a deck porch roof where the contractor had face-nailed through the roof beams into the wood posts. In other words, he had a 4x4 post and a 2x6 beam nailed to each side of the post. There was nothing that the 2x6's were bearing on, they were just nailed through into the post. If the loads are such that several nails can handle the load in shear, is this still considered bad practice without putting something under the 2x6 to bear on? I know Simpson makes a steel bracket for this exact connection. I ended up just having him trim out the post with some 2x's just under the 2x6's so that they were bearing on something. But did I really have to make him do that if the nails were sufficient?

 

[hokie66]

The nails are not sufficient, especially in an external environment. You did the right thing. That contractor is a lazy moron.

 

[4thorns]

hokie,
Please take no offense to this but I guess your statement confuses me a little. Obviously without knowing the design loads for this particular case it's impossible to determine if the nails are adequate to support the 2x6 beams. But to say flat out that "The nails are not sufficient, especially in an external environment." makes me wonder why we would have design values for nails if we can't use them. Are there no situations where for instance: there was no snow load and other loads were minimal that it would be ok to rely on nails to support the roof? The only reason I ask is that it seems to me that this could be treated as a ledger, say for deck joists. As long as the fasteners can handle the vertical load assigned to them then it's possible for them to work. Any thoughts?

 

[dhengr]

4thorns:
Hokie’s right on the money, nailing that post/beam joint in shear is not a good idea, inside or outside. The ledger is loaded ever 16" o/c (almost uniformly) and it can be nailed every few inches o/c if needs be to pick up the joist loading, and distribute it into the structure. The double 2x6 beam on two 4x4 posts, with one 2x6 beam on one side and one on the other side of the posts, is loaded much like ledger, at 16" o/c (almost uniformly). But, there are several problems; the load is taken out at only two post, not every few inches, so you may not be able to get enough nails in the two joints without splitting the beam or the post. Secondly when you space the 2x6's that way, and the joists deflect under load, there is a good chance that the joists will only be loading one of the two beams, they will not be acting as one unified beam, and this adds to the connection problem. Finally, nails in a wet application have a nasty tendency of rusting through right at the joint faying surface in a very short time. All the more so with nails of unknown origin and smaller dia. shanks. This latter condition exists at the post/beam and at the ledger connection since those joints tend to get wet in the rain and then take days to dry out.

 

[hokie66]

Thanks, dhengr. Maybe there is only one post as the OP said, but nails should not be relied on in this manner. These are roof framing members in an exposed environment. I wouldn't use the detail internally either, but some might, if they haven't seen what nails look like after 10 or 20 years inside a joint.

 

[shaneelliss]

Thanks guys. I think the message I am getting is that even if the loads at the nailed joint calc out ok with just nails, it is not good practice to do so because of long term effects and lack of redundancies. Thanks again for the input.