spliced floor joists

[charles]

In the March 2010 issue of Builder magazine, spliced floor joists are discussed on page 87, which you can see at http://mydigimag.rrd.com/publication/i.php?i=35451&ver=html5#{%22page%22:88,%22issue_id %22:35451}

They don't lap the joists over the center beam, they splice them no more than 1/3 of the span from the beam.

Has anyone ever done this? Can it be done for simple spans or rafters?

[dgbldr]

Re: spliced floor joists

I haven't and I wouldn't. I would have to provide engineering to prove it's equivalent to the prescriptive member.

That write-up makes no sense where it claims the offset splices are better because splicing in the center would be weaker.

It also doesn't make sense economically. You would want to use the shortest pieces and have them all same length.

[James Eggert]

Re: spliced floor joists

The "suggested" 14% savings is also questionable because adding two splice plates, labor to screw around with lumber hanging in the air WHILE making sure the top plane stays flat is laughable. Sure, it can be done but is it productive cost savings or feel-good approach on one simple area of the floor framing package?

However, you give me a stamped drawing and if the spans are short enough and I feel comfortable with it I'll sign off on it, but in general I don't think it's a prudent approach. Taking a 16' member and a 14' member using that approach would give you 30', but using single I-joists would have the floor framing in-place before two guys could do 2-3 splices! Trying to crown the members and then splicing them on a flat surface just increases the weight issue such that now you need 3-4 guys to move them into place.

"when you value engineer, Miller says, everyone and everything wins!"

NOT when you don't include all associated costs for doing something. Green is good, but not always appropriate for every aspect of building. No one is going to build saving 15% on material costs and drive their labor costs up more than the savings. I don't mean slight differences but when labor costs spiral materials suffer because of trying to save more than is practical.

[dgbldr]

Re: spliced floor joists

However, you give me a stamped drawing...

Exactly. It costs more to have the calc/drawing by an engineer than you'll ever save AND it will look cheap and questionable for the life of the building.

[tomthetoolman40]

Re: spliced floor joists

What's even more laughable is the scrap engineered stud.

Who's gonna spend $10 in labor to save $4 on a stud?

(Scroll the article one page to the right to read about it.)

[Happy Home]

Re: spliced floor joists

This looked like doo-doo when I saw it...

Mending plates in the field, just for starters ?

How do you crown those ?

Mentions better than upgrading to 2x12's... I learned to avoid 2x12 FJ for a few obvious reasons.

[frenchie]

Re: spliced floor joists

I'm just the carpenter... but if someone told me to splice joists midspan with a mending plate? or assemble studs out of scraps? I'd start looking for a new job.

[Phil_H]

Re: spliced floor joists

I think James Eggert hit the significant points. Even if the engineering were free, it probably would cost more to install and be more trouble than it is worth to use at joists. However, this scheme is frequently used on glulams. Simpson makes the HCA for connecting the glulams.

By the way, I think this is my first post. I am an engineer that does very little with wood and almost no light construction. (mostly structural steel)

[dgbldr]

Re: spliced floor joists

Pas de merde, as we say in French. Now I remember why I never subscribed to that magazine :)

[jimAKAblue]

Re: spliced floor joists

Theres a lot of fuzzy math going on.

The author says that if I splice a 12' and an 8', I can span 20'. His alleged savings come from eliminating the higher priced 20'ers from the lumber list. Who orders 20's? No one. I'm quite sure we all would order 10's.

The author wants us to double the rim joist to eliminate the header. Now I'd have to add joist hangers to carry the floor joist. Sometimes this makes sense in very rare cases.

The author urges me to use my "scrap" pieces to create studs. Sorry, we are already using ALL of our scrap pieces. I quite often have to cut small blocking out of plate stock because there isn't any "scrap" lying around.

I do agree with eliminating extra cripples in windows. Adding the extra ones against the trimmer studs is wasteful. They serve no useful purpose other than "that's the way my granddaddy taught me". I don't always eliminate them because I don't want to have the discussion with the builder, inspector or the homeowner's uncle who thinks that "only a hack would cut that corner".

[Slaughter Construction Co]

Re: spliced floor joists

Doable yes. Practical, not so much in residential construction.

Without pulling out the books, this works on the principle of continuous spans. At some point from the interior support, there is a specific point where the bending moment is zero and you only have to deal with the shear forces at that point.

At one time, there was a metal connector made that would be fastened to the end of one joist that would support the end of the adjoining joist. It was similar to joist hanger. I don't know if SST makes one or not.

In reality, in some situations, you could actually reduce the size of the joist using this principle. It is used in bridge building where multiple spans are common.

Maybe someone will come along and explain it better.

[johnny watt]

Re: spliced floor joists

Not sure if you can see the beam connection in this photo about 6' to right of column which my engineer designed. The connection is completely on the "I" portion of the beam while the top and bottom flanges are ignored. I could be wrong, but I would think that design is dependent on the cantilever beam it is attaching to, being larger.

I think joist splices and stud splices should be reserved for repairs. And I would trust my truss designer to spec out such splices more than anyone.