Multi-story Residential Steel Columns

[L_D_]

When putting in a steel column on a floor higher than a basement, what is a typical detail to get a load path through the wood framed floor? For instance, if there is a beam supporting ceiling joists on a single-story house, a supporting column would have to be ~16' long (8 foot story height plus 8 foot basement height) to get to a footing. That seems impractical, so are 8 foot columns typically stacked? If so, what is a typical detail where they meet? A direct connection or is there blocking between them within the floor framing? Thanks!

 

[jayrod12]

Often they are stacked. However the more that I think about this, it's generally uncommon. I've really only needed steel columns in multi-tenant multi-storey wood framing and even then it's normally only at the bottom level of wood framing which usually sits on a concrete transfer floor.

 

[LuK13]

I've seen columns continuous through two stories on two occasions. Both were installed during new construction so they were just lifted into place before the roof was on, no real issue if you sequence the construction for it.

On one occasion I was there for an unrelated reason and I picked up on the fact that the EOR had the column landing on the top of the foundation wall with a pilaster. The contractor elected to skip the pilaster and bring the column down to the footing beneath the basement slab. I just flagged it for the EOR to review because I didn't know what unbraced length they used and was worried the contractor was just ignoring the drawings.

Its not impossible to have a tall column, but its going to depend on your jobs details.

 

[KootK]

1) A 16' single lift steel column is pretty common in my experience.

2) If loads are heavy enough to justify the use of steel columns up multiple levels, they're usually also heavy enough that I get uncomfortable trying to pass them through blocking etc. Once I go steel, I mostly like to stay steel as I move further down the load path.

3) In opposition to #2 is the desire to stuff some wood in there to encourage compatible shrinkage between the steel column assembly and the other stuff nearby.

 

[driftLimiter]

Agreed with Kootks (1,2,3)

If you have (3) stories or more think about KootK's #3).... watch out for differential shrinkage. Also consider continuity of double plates at post locations.

Personally I like the continuous post detail better in 1-3 story custom homes, I see this done a lot in my area. With the way that steel vs wood is framed it often makes a lot more sense to install full height steel columns, then come back with the framers and finish the walls etc.

 

[dik]

Often do them at each second level, with the spice located 1'-6" above the floor if detailing permits it. My latest project, a six storey addition with a PEMB at the top is all mechanical rooms at ea level and can easily use the splice above the floor at ea second storey.

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[L_D_]

Thanks for the very quick responses. The job that prompted this question is a retrofit, so getting a 16' column in isn't feasible. I was going with a steel beam to take out a load bearing (ceiling joists only) wall while limiting beam depth on a ~20' span. I thought it would make sense to use steel columns as well, but I am open to other options. I haven't done a lot of residential projects but figured this was a pretty common modification. This is only an issue for one of the columns, because the other can bear on the CMU foundation wall.

 

[KootK]

Where the need for a steel beam is pretty much entirely a function of deflection control, I quite commonly support steel beams on wood posts. It simplifies a lot of things from a detailing perspective really. If it's a stacked joint, just be sure that you've got the joint stabilized against beam rotation etc.

 

[L_D_]

KootK, a follow-up question if you don't mind. An adjustable height steel column would have been very helpful in a retrofit situation since the height of the ceiling joists and the floor framing are existing. If I go with wood columns, any ideas about getting the column height correct without adjustability?

 

[KootK]

If I go with wood columns, any ideas about getting the column height correct without adjustability?

Order them long and cut them to fit on site? Teleposts are pretty great in situations where adjustability is a significant benefit. Other than awkward shimming strategies, I don't know of a robust way to obtain similar adjustability from a wood post.

 

[RWW0002]

Check out these...

https://www.strongtie.com/miscellaneousconnectors_woodconnectors/j-jp_jackpier/p/j.jp

[URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1663963963/tips/C-C-2021-p317_qpdp4k.pdf[/url]

 

[HouseBoy]

I've done it both ways (continuous steel column and individual columns bearing on wood blocking).

A few things:
I work on single family residential projects only. Some contractors "like" steel and some "hate" it. USUALLY that has to do with the lower ease of field adjustment. Still.... it's always an adventure to find out what they will tolerate. Sometimes it is the weight of steel that they don't like. As far as "adjustability" - they all seem to be able to cut to length and get a tight fit pretty readily.
I wonder what the load in the column is that "requires" you to use steel.
I assume you are not supporting masonry with the column (not allowed to support masonry on wood unless it is separated from other masonry with a CJ)
Usually wood crushing is the thing to be looking at.
For that reason, I'd want to be careful with the adjustable end type columns. (Also, I want the adjustable end at the bottom.)
Also, when wood drying shrinkage is a factor, I specify "LVL material only" to be used for blocking and/or "vertical grain orientation only".