I inspected this house today. I believe it was around 1940s. There was a steel beam down the middle with tiny 2x3 “joists” running parallel to the steel beam. Then there were steel web truss joists running perpendicular to the center steel beam–only six of them mind you about 4 feet o.c. That wouldn’t be so bad but the thing was that only the top of the web trusses was connected at the outside concrete walls. The bottom of the truss wasn’t even connected and then once again at the steel beam there was only connections at the top. The bottom wasnt connected. It should be said that this was a popped top so weight was added to the structure but I’m really not sure when these trusses were added or if they were original for that matter. I welcome your opinions. Thank you.
The steel trusses are unconventional for residential construction in my area. If I did not feel confident standing behind such design, I would advise the client to consult with the seller to show engineer approval and building permit that shows this was approved. Otherwise, I’d defer to an engineer to okay it. It would be beyond my pay grade as a HI.
Agreed. That is definitely what I was thinking as well.
Very well worded Simon…unconventional indeed!!
If you look carefully the steel I joists on the left side seem to sit on the I beam girder and the right I joist visible on the right sits away from the I beam girder. The wood runners going parallel to the I joists appear to be spaced further apart than they should be, which may result in the floor having excess bounce or deflection. You need an engineer to inspect this. Very unusual for a house. The I beam girder is not all that uncommon but the steel I joists which are typically seen in commercial construction is certainly an oddball.
If they don’t have the stamped/sealed paperwork for the design by an architect or engineer and the approval stickers from the local building department this is something that needs to be checked by a professional engineer.
Unconventional but not wrong. Modern Residential construction uses wood versus metal trusses. Metal is common in Commercial. The general design and attachment of the “Top Cord Bearing” floor trusses themselves are correct, but I do question the load bearing capacity of the entire system. Without knowing more information regarding the subfloor construction detail, (4 ft o.c.), I would definitely call it out for review and correction as necessary.
Refer page 34 for Top Chord bearing graphic…
http://www.cascade-mfg-co.com/media/a-builders-guide-to-trusses.pdf
Ok. Just making sure I’m not crazy but that was my thought as well
That is rare to see steel web joist in a house of that age, but I don’t see anything wrong with the framing the way it is for a 1940 build. The joist are bolted to the beams and likely welded to a steel plate on the concrete wall.
What you might see different in today’s world are sleepers bolted to the top flange of the joist and a 1-1/8" thick sub-floor.
Doesn’t hurt to call it out, but I am sure it will stay like it is.
Have to agree with Marcel. Unconventional, for sure, but it has been around for longer than, most of us, have been alive. 
Cheers
I was an ironwork for 12 years. We called them bar joist. I would just check to see if they were welded on both ends and that they had a steel plate embedded in the concrete wall. Looks like maybe the one side is bolted on. We would also run bridging which was an angle iron welded to the bottom cord that kept them from rolling.
Not much rolling effect with those little K-Series joist. 
The name > bar joist came because of the use of round bars used in the webbing.
Now it is open web steel joist because of the angle shapes used in many of them.
So can I safely throw a 30 24oz-steak-loving-texan humans party on this floor or not, show me the mathz! 
Need to know the thickness of the subfloor![DSCN0208-Copy|640x480], but I would not worry about 30 psf. I have seen worse and it carried 80 psi and the joist looked like this;
This may help some.
http://www.cascade-mfg-co.com/media/1101-TS-Floor-Truss-FINAL.pdf
edit: I see Jeff already posted this link.
are those 4’ OC?
The PDF does not mention 4’OC spacing. How do we know the OP has the same design as TrusSteel? same welding, same gauge metal? HI is supposed to figure this all out the single time they see this in the field?
Come on guys, keep it simple for us We’re not smart like you old guys
This link here might help more https://civil.colorado.edu/~willam/4830%20Vulcraft%20Bar%20Joists.pdf
And the ASD for the OP’s web joist would be 666 plf for an 8K at 12"
or 825 plf for a 10k at 12’
ASD= Allowable Strength Design
An no, a regular HI is not required to know this. But in my case of so many years in commercial and industrial building and associated with design engineers, I can usually tell if something is wrong.