Floor Joist Seen some I had never seen before.

[mrmurdoc34]

So the wife and I stopped and looked at a house we would like to own. It has been on the market for 2+ years. It sits on 5 acres and the house is a 4 bed 4 bath 3100 sqft ranch. The guy who had it built went above and beyond. He had the cabinets custom built on site. All the doors are 36" SOILD OAK 6 pannel. The basement is unfinished and has 10' between the floor and joists. Now the joists are one I had never seen before. They were a 2x4 on top and bottom and linked together via a stamped galvanized steel shaped like a zig zag they were a solid 36' in length. They were beefy and said to be high end stuff. The flooring was some kind of plank high end vinyl flooring that looks and feels just like hard wood.

Has anyone ever seen this type of joist? Just wondering what the name or manufacture is.

[havasu]

Sounds like a special order z-type girder system. This allows a low cost (compared to finding a 36' long piece of wood) structure to accomodate long spans. There are actually hundreds of manufacturers, which all use various inserts. I've seen steel I-beams, aluminum, wood, galvanized, and metal piping to make up the structure.

[RiponredTJ]

I think they are called open-work or open-web joists, if they look like number 3 below. They are pretty common up here.

[mrmurdoc34]

Rip your nailed it. #3 is a dead ringer. Thank you.

They were made by a company called Space Joist.

[blucher]

Space Joist etc.

I had little idea how complex a joist structure can get let alone how much hardware may be required.

[rivalarrival]

looks pretty sturdy. Ought to make plumbing and wiring a hell of a lot easier, too!

[blucher]

Originally Posted by rivalarrival

looks pretty sturdy. Ought to make plumbing and wiring a hell of a lot easier, too!

This thread made me aware I have no idea about the purpose of floor joists other than as an aid in getting a floor level. It appears to be a huge amount of adjustments.

[rivalarrival]

Originally Posted by blucher

This thread made me aware I have no idea about the purpose of floor joists other than as an aid in getting a floor level. It appears to be a huge amount of adjustments.

Floor joists sit on beams and/or the foundation walls, and support the floor span. There's generally no adjustments to be made at the joists - adjustments are usually made at the posts supporting the beams supporting the joists.

[blucher]

Floor joists sit on beams and/or the foundation walls, and support the floor span. There's generally no adjustments to be made at the joists - adjustments are usually made at the posts supporting the beams supporting the joists.

Then once all joists were beams of wood but commonly replaced by synthetic beams called joists?

Since a great many houses were blown off their foundations in the recent tornadoes would this joist install time also be used to further anchor frame & foundation?

[rivalarrival]

Originally Posted by blucher

Then once all joists were beams of wood but commonly replaced by synthetic beams called joists?

Since a great many houses were blown off their foundations in the recent tornadoes would this joist install time also be used to further anchor frame & foundation?

The definition of "joist" doesn't depend on its composition, but its purpose. Whether the subfloor sits on 2x10 wooden boards, or one of these engineered structural members, the thing the subfloor sits on is called a joist.


Got a full basement? In most basements, there are posts, vertical members that support a big chunk of wood. That big chunk of wood can be a 10x10 tree trunk, several 2x12 boards, a solid steel I-beam, etc. That big chunk of wood typically runs the full length of the basement, and it's usually the lowest horizontal, structural member in the ceiling of the basement. If you have to duck when you walk across your basement, the beam is the thing you're most likely to hit your head on. (If you have a crawlspace, the construction is similar.

The top of the basement walls is called the "sill". The top of the beam is the same height as the sill. The Joists sit on top of the beam and the sill. On top of the joists is the subfloor, usually a sturdy plywood.

I've never seen a renovation go so far as to replace more than one or two joists, and then only in extraordinary circumstances. Once they go into new construction, they typically stay put until demolition.