Help with floor truss design

[ACDNate]

I'm working on developing a framing plan for the first 20x30 bay in my shop that's under construction.
http://www.garagejournal.com/forum/showthread.php?t=252685

I will be enclosing the first bay, and bathroom with traditional stick framing. 2x4 @ 16" centers. The second floor will be utilized for storage of household items, Christmas tree, lights, and other assorted **** we don't need but hold on to for some odd reason.

The area below will have drywall finished on it and a run of HVAC duct work. Essentially a party room, gathering area.

I'm trying to determine what sized floor trusses I'll need to use. I will talk to a factory rep before ordering but i'm trying to get costs estimated ahead of time.

Longest span is 20'.

Anyone have any advice or links to help calculate what I'll need?

 

[Nowater]

Around here if the space is a commercial space, any storage such as you describe needs to be engineered. The engineer will determine maximum loads allowed based on the construction. If people from the party went up there, how many people could fit in the storage space?

 

[Zeke]

Floor joists. Depends on span and live load. Budget for big.

 

[ezzzzzzz]

I used 16" engineered beams on 16" centers for my 22' span. They are as solid as concrete...no noise...no flex.

 

[Chris705]

20' span for light duty (30psf attic type) storage would be my opinion to go with 2x12's at 16"oc....use hemfir. Provide a couple rows of bridging and use 3/4" t&g subfloor glued and nailed. Not sure if the 12" dimension is adequate for your ductwork? Otherwise one of the I-joist products could be quickly engineered for your required depth and span.

 

[CJCar]

Floor joists. Depends on span and live load. Budget for big.

If floor truss is in fact what you are after, here is the first google hit for a span table:

http://www.socomp.com/wp-content/uploads/2014/02/FloorSpan.pdf

 

[ACDNate]

Around here if the space is a commercial space, any storage such as you describe needs to be engineered. The engineer will determine maximum loads allowed based on the construction. If people from the party went up there, how many people could fit in the storage space?

Not a commercial application. This building is in my back yard.

 

[ACDNate]

Floor joists. Depends on span and live load. Budget for big.

Live loads is kind of what I was looking for information on. WHat kind of load to plan for. 40psf, 50psf, etc?

Also what deflection limit to use, L/360 or L/480?

 

[Zeke]

Live loads is kind of what I was looking for information on. WHat kind of load to plan for. 40psf, 50psf, etc?

Also what deflection limit to use, L/360 or L/480?

You really do need a structural engineer.

 

[BFBOB]

At the risk of opening a can of worms, has anyone tried building his own "engineered" joists? Wood I-beams are certainly simple enough. Rout a slot in the flats of 2x4's and glue in 1/2" plywood for the web with construction adhesive - or good ol' Titebond III.
Longest 2x4's available long enough to be worth the effort? 16'? 20'? The strength is in the flanges, so having the web non continuous wouldn't be a serious compromise (though I think I'd join them with a t&g anyway.)
Copy dimensions of commercially available wood-I's and derate the load a bit for good measure. What could go wrong?

FLAME SUIT = ON

 

[ACDNate]

At the risk of opening a can of worms, has anyone tried building his own "engineered" joists? Wood I-beams are certainly simple enough. Rout a slot in the flats of 2x4's and glue in 1/2" plywood for the web with construction adhesive - or good ol' Titebond III.
Longest 2x4's available long enough to be worth the effort? 16'? 20'? The strength is in the flanges, so having the web non continuous wouldn't be a serious compromise (though I think I'd join them with a t&g anyway.)
Copy dimensions of commercially available wood-I's and derate the load a bit for good measure. What could go wrong?

FLAME SUIT = ON

In theory it sounds possible. Not sure you would save any money doing so though.

 

[Kevin54]

In looking at the Pocket Reference Guide, to get your 20 foot span, you're looking at a lighter live load, and a light dead load, and using a 2x12 Southern Pine joist at 12" or 16" on center. Most of the other pines fall short by a foot or so, then of course as the loads go up, the span goes short.

It looks like you will have to go with either engineered floor joist, or if you can get a 30' LVL, then use 10' joist on either side to get your 20'.

If per chance you can have a support underneath somehow, like a supporting wall, then you would be good to go with 2x12's x 20' long with no problem.

This is basically the same thing in the Pocket Reference Guide. You'll notice that about the closest is the Southern Pine, but at 12" on center.

Or take a look at the engineered trusses here

http://www.roseburg.com/Product/rfpi-joist-lvl-flange/



`

 

[ACDNate]

So I was looking around at other engineered products mentioned in this thread. My assumption has been that trusses were typically the least expensive option. LVL's are insanely expensive.

Since Menards list pricing on various engineered products I used their site for comparison. I narrowed down to 20' span lenghts and found two comparable sized pieces

11 1/4"tall 2x4 truss $65.99

11 7/8" tall 2 1/2" I joist $30.80

I don't know much about the Ijoists.

Has anyone used them before? Installation issues? Any oddities I need to know about them?

 

[Chris705]

So the hem fir 2x12's at 16" oc will give a span of 19'-11" for a 40psf load and L/360. That equates to a typical floor loading used in any main floor residence. It can also handle drywall w/o cracking. The hem fir should be available at any full service lumberyard for less than $35 apiece.

 

[BFBOB]

I've worked around, but not installed, both trusses and wood I-beams. The folks who swing hammers say the Ibeams are cheaper load-for-load and lighter, but much harder to run utilities through - especially HVAC. In a garage that might not matter much, and drilling the thin web for electric is no biggie. I was just thinking for a DIY, building trusses doesn't seem very feasible, but I-beams does. Price? Don't know. I did a bit of web crawling, found some local lumber yards that carry 2x4x20', but no prices. Ditto -Ibeams. If I were undertaking the project any time soon, I'd dig deeper, but for now it's a mental exercise.

 

[ACDNate]

I've worked around, but not installed, both trusses and wood I-beams. The folks who swing hammers say the Ibeams are cheaper load-for-load and lighter, but much harder to run utilities through - especially HVAC. In a garage that might not matter much, and drilling the thin web for electric is no biggie. I was just thinking for a DIY, building trusses doesn't seem very feasible, but I-beams does. Price? Don't know. I did a bit of web crawling, found some local lumber yards that carry 2x4x20', but no prices. Ditto -Ibeams. If I were undertaking the project any time soon, I'd dig deeper, but for now it's a mental exercise.

Just using Menards website as a guide, the I joists are cheaper by a decent amount. If they're lighter that will help with assembly for sure. I have access to vendors that carry both and will get me a better price than typical retail. Still don't want to spend more than I have to.

I do need to figure out how the installation of an I joist would work in my application. Still digging...

 

[Nowater]

Yes, I built my own trusses on a ten feet wide shed that I did not need a permit for. That being said, yes I am an engineer!

 

[BFBOB]

OK, I looked at Menards. 2x3x20 I-joist $31.(they don't carry the 2/4 I-joists) Materials to build 2x4x20 I-joist $26. But, it would take half again as many 2x3's (12"OC vs 19.2"OC for 11 7/8" depth), so ... would it be worth my time to build them? Not really, unless I had nothing else to do - yeah, like that would happen!

Before deciding fo rsure, I'd need to see a price on 2x4x20' I-joists, but I suspect it would make building my own even less feasible.