4x4 posts have to be 4" by 4"? that's crazy and makes no sense for an engineer in los angeles (or louisianna, wherever you are) ..

are they exposed, and therefore rough cut dimensions?

I'm not sure what you're asking: are you asking if ganged 2xs can be substituted for a single 4x, or are you asking why the engineer specified an actual 4" wide piece of wood, which is not as commonly available as a 3.5" piece of wood?

Well, they will be 3.5x3.5 ..but we cant DOUBLE up to make stud packs.. The engineer is making us get all the structural members 4x...I was surprised.. its certainly not a post and beam house.....also, I have just had my first debacle with seismic requirements... (basically the whole house is one big shear wall)

So are you saying that where the engineer specified a 4x4 post (actual 3.5x3.5) you are required to install and single 4x4 member and cannot make a built-up post composed of (2)2x4's?

We do built-up posts here in the northeast all the time. I've never had to glue up a multi-member post either.

Does it have something to do with the connection, for example, is a particular Simpson Strong-Tie connector spec'd that will only work with a 4x? Seems unlikely, but maybe...what is the 4x4 being used for, I assume a post?

build up posts or doubling up on anything(horizontal members) to make up for the next size is not allowed here in LA.
maybe the nominal size is only spec'd for the foundation wall plates? they are nominal sizes (green treated lumber.)

I’m not familiar with your local codes, but slapping a pair of 2x4’s together does require analysis to get them to function compositely. In compression, arbitrarily connecting them together with some arrangement of screws might be enough, but you may not provide enough shear flow to resist the 2x4’s buckling independently of one another, and thus not providing the capacity of a true 4x4 column. So the engineer has a point in asking for the originally specified section.

Also, for what is worth, the term “nominally” comes from the Latin word for name. Nominally, a “2x4” is a “2x4”, while actually a “2x4” is 1-1/2”x 3-1/2”. It is just a little pet peeve of mine; a lot of people get it confused.

I agree with Synergy.

I would think there would be more unquantifiable data as the adhesion or fastening (2) 2x4s could be inconsistent, for seismic design. It might require more work down the line to get that done properly, which at the end of the day might not be worth it. So I think its more of an issue of quantifiability and reducing the number of variables, than actual strength or feasibility of using (2) 2x4s.

why not just call the engineer and ask him?

synergy, thats what i said too. green treated lumber commonly used as foundation plate here in so cal, comes with 'nominal' 2x4 (beefy)



also in houses built around and before 20's in los angeles, you encounter beautiful old structural redwood lumber which is naturally resistant to termites etc. and they are nominal sizes too.

it would be insane for an engineer not to calc. 'actual' sizes at this day and age. are you sure?

Definetly, a person has to spec and calculate based on the cross sections that will actually be in use, just like they have to use realistic values for the allowable stresses (which in lumber can be quite variable).

and we should add that it would be also insane that it is not picked up by the architect, plan checker, contractor, etc... before it arrives to order desk.

also, can you imagine the chaos it would cause during the construction anywhere from nail sizes to tooling to hardware to, you name it.?

Thanks for the feedback guys..

Well I asked him today..( the engineer).."no ganging of 2x's to make a 4x in LA"..is all he said. Sounds like slartibartfast was right here...Moreover, he also made me change my sill plate to 3x due to some shear wall nailing requirements.
All sounds pretty weird to em, but whatever..makes for interesting debate I guess.

I guess modern day seismic design is just crazy.

it's all about survivin' that 8.0!

when i see homes framed in the midwest it makes me nervous, like they're just gonna tip over (i'm used to seeing lotsa moment frames, shear walls, simpson strong walls, etc ..)

Ahh the mid westerners probably feel about the same about your roof designs. You mean you don't design for a 150psf drifting snow load!?!

i've worked on homes in the ski resort of sun valley, idaho. the homes there typically have a 'cold roof' to prevent killer icicles at the eaves and the roof framing was of a similar beefiness to anything you find in southern california.

Yeah, hailing form Denver, I have worked on a project that had 14" TJI rafters.

When I got to LA,...I saw all those dingbats with two little pipe columns under them and thought ok well, that should work...but I learned the hard way that they don't let you do that anymore. You have to bring out the out the 5k$ wide flange moment frames. Maybe I'll post some photos

or maybe your experience in other parts of country is fooling you.

i was here in japan when kobe was flattened by earthquake. lots of people died. it was not a pretty sight and there was a lot of suffering all around.

fucking with seismic requirements and codes is just not responsible.

duly noted.