Large floor joist spanning?

[jfw432]

Hey guys, I'm fairly new here but have read a few good articles on this site. I've been dreaming about adding a garage on the back of my house for some time with a deck on top (aka no roof). I'm looking at a 24x24 ft garage and would like to keep the floor space clear of supports.

I'm an engineer by trade but work with airplanes and metal instead of houses and wood so bare with me as I'm not familiar with what's allowed or standard practice. I was wondering if it's possible to splice some 2"x12"x12' joists together with a 12" spacing to span the 24 feet or would I be forced to use floor trusses or steel I beams for a span this large? If it is too large, could I get away with 20ft or 22ft instead?

If splicing is an option, I can think of tons of ways to splice wood together but what is the appropriate way to do it? Simpson straps, steel plates, bonded wood, nailed wood, bolted wood?

Thanks in advance.

 

[Dustball]

Where are you located?

Snow loads, earthquake-prone, hurricane area, etc...?

 

[6t7gto]

use I-joists

 

[jfw432]

use I-joists

Is this something you build or buy?

Where are you located?

Snow loads, earthquake-prone, hurricane area, etc...?

I'm in GA so none of those really apply.

 

[Thumper68]

I second the I-joist It will be your best bang for the buck. If you call up your supplier (Lumber yard) they will be able to size them for you.

 

[6t7gto]

http://lmgtfy.com/?q=wood+i-joists

 

[Thumper68]

Is this something you build or buy?



I'm in GA so none of those really apply.

You buy them.

 

[kbs2244]

Price competitive with wood "I" joists would be a steel "I" beam down the center with 12 foot joists resting on it.
The shorter span will be stiffer.

 

[mharris2007]

use I-joists

This.

I just built an attic for my garage. My engineer engineered the attic to hold 20,000 pounds or 6 honda civics, lol. There is a beam that spans 24 feet then the ijoists are 14 feet on one side and 8 feet on the other. If you don't plan on it holding anything ultra heavy, ijoists would span 24 ' fine.

When I was deciding between dimensional lumber or ijoists for my attic, you had to buy the best (most expensive) species of lumber for it to be sufficient across 24 feet. This was for attic space mind you 16" on center. Good luck.

 

[jfw432]

http://lmgtfy.com/?q=wood+i-joists

Come on man....seriously? How about explain your original post just a tad better? I wouldn't tell you to make a carbon fiber airplane and show you a picture of dry carbon fiber cloth. I'm just trying to figure out if you're suggesting building one or buying one. It's not like a regular "off the shelf" item at Lowes or Home Depot so I'm here looking for a little bit of clarity. I've done plenty of research but every search ends the same way....lots of specs, no price, no idea who makes them, and no idea how they're assembled.

I've never used a lumber yard before so this is new territory to me. Most specialty shops I've dealt with in the past are in business for other businesses and usually want a license number before even giving me the time of day. Is a wooden I-joist common enough that any lumber yard would have them? Do they custom make them or have them lying around?

 

[csp]

I second the I-joist It will be your best bang for the buck. If you call up your supplier (Lumber yard) they will be able to size them for you.

Key information here. Call a lumberyard, meaning a real lumberyard, not Home Depot or Lowes.

Chances are you're going to have to have structural engineering drawings for any building permit, so if you're serious go find an engineer that does this sort of work.

 

[jfw432]

This.

I just built an attic for my garage. My engineer engineered the attic to hold 20,000 pounds or 6 honda civics, lol. There is a beam that spans 24 feet then the ijoists are 14 feet on one side and 8 feet on the other. If you don't plan on it holding anything ultra heavy, ijoists would span 24 ' fine.

When I was deciding between dimensional lumber or ijoists for my attic, you had to buy the best (most expensive) species of lumber for it to be sufficient across 24 feet. This was for attic space mind you 16" on center. Good luck.

I have definitely given this a lot of consideration because I can do the math for a metal I beam. Still need to find one and if it's economical enough, figure out how the heck me and some friends are going to move something like this. I'm guessing around 200-300lbs for one of these without the supports.

 

[Thumper68]

Come on man....seriously? How about explain your original post just a tad better? I wouldn't tell you to make a carbon fiber airplane and show you a picture of dry carbon fiber cloth. I'm just trying to figure out if you're suggesting building one or buying one. It's not like a regular "off the shelf" item at Lowes or Home Depot so I'm here looking for a little bit of clarity. I've done plenty of research but every search ends the same way....lots of specs, no price, no idea who makes them, and no idea how they're assembled.

I've never used a lumber yard before so this is new territory to me. Most specialty shops I've dealt with in the past are in business for other businesses and usually want a license number before even giving me the time of day. Is a wooden I-joist common enough that any lumber yard would have them? Do they custom make them or have them lying around?

If you call a real lumber yard, they will be able to spec and order the I-joists that you need. They usually do not have a engineer on staff and will contact the manufacturer and they will do the load calc, it usually takes a week or so to get the specs and a few weeks to deliver after the order.

 

[Thumper68]

Have to add:

Depending on your AHJ you might need stamped prints to get the permit. to get those you will have to pay a engineer to go over any plans and stamp them. I had drew up some for a customer a few years back and had to take them to a engineer for a stamp, they charged me $350.00 with no changes. Of course the stamp also comes with them accepting liability for the specs as well.

 

[jfw432]

If you call a real lumber yard, they will be able to spec and order the I-joists that you need. They usually do not have a engineer on staff and will contact the manufacturer and they will do the load calc, it usually takes a week or so to get the specs and a few weeks to deliver after the order.

Thanks!

 

[Dustball]

My house is a raised ranch meaning my living space is entirely over the garage. In order to have a clear span of 28 feet depth in the garage, 22" tall open web floor trusses were specified at 19.2" spacing. Seeing how houses and decks both need to meet 40PSF live load, you're probably looking at close to the same truss dimensions except you're four feet shorter. Keep in mind you have to also accommodate the weight of your roofing material and decking material.

 

[gpflepsen]

C'mon man! I like your *****. :}


Engineered lumber used according to the manufacturers span table often precludes the need for an engineered stamp. The design is already done and incorporated into the product literature. You need to understand where your inspector will be coming from and his requirements on this.

I would definitely look at the live loads and deflection that you're comfortable with. Having a bouncy deck would **** in my book. This would probably force you to upsize the joist to lessen the deflection. I'd explore the I-beam solution already mentioned for cost and buildability. Larger I-joist are easily manageable, but the I-beam will take some muscle.

 

[dfiler2]

My shop is 26' wide 14" I-joists 16"OC w/ 3/4" T&G decking and Its very solid. You can also use metal bridging to take out the bounce.

 

[theoldwizard1]

First you need to know what the load is. This is going to be difficult because you want a deck on top, plus you have the "live load" of people walking on it. Once you know the dead and live load, there are tables you can look at for the proper joist size.

Likely you will have to go with a wooden I-beam or, worst case, a parallel chord floor truss.

 

[6t7gto]

Come on man....seriously? How about explain your original post just a tad better? I wouldn't tell you to make a carbon fiber airplane and show you a picture of dry carbon fiber cloth. I'm just trying to figure out if you're suggesting building one or buying one. It's not like a regular "off the shelf" item at Lowes or Home Depot so I'm here looking for a little bit of clarity. I've done plenty of research but every search ends the same way....lots of specs, no price, no idea who makes them, and no idea how they're assembled.

I've never used a lumber yard before so this is new territory to me. Most specialty shops I've dealt with in the past are in business for other businesses and usually want a license number before even giving me the time of day. Is a wooden I-joist common enough that any lumber yard would have them? Do they custom make them or have them lying around?

http://www.menards.com/main/building-materials/engineered-products/i-joists/c-5662.htm

You're the "engineer", now all you have to do is figure out your live load and dead load.

 

[rburke65]

I-joist....picture a wooden "I" beam with the center web of plywood and the upper and lower flange being a 2"x4" and you will have a rough visual. They have been in use for years.....invented in 1969. Good luck and keep us posted.

 

[larry4406]

I would look into open web floor trusses. They span long distances. Then build a sleeper system on top to pitch the roof below the deck. Coat the roof with EPDM rubber to seal it. Then your deck bears on the EPDM (dead weight, no punctures).

 

[jfw432]

http://www.menards.com/main/building-materials/engineered-products/i-joists/c-5662.htm

You're the "engineer", now all you have to do is figure out your live load and dead load.

Thanks. I saw those and I wish I had a Menards somewhere even remotely close to me so I could price those out and compare it to the other options.

 

[kbs2244]

Everybody has been ignoring the issue of "stiffness" in the floor above.
Open web, and even some solid wood web "I" jousts have fallen out of favor because they just do not have a "sold" feel.
They do meet all the load bearing specs but people feel a flex or "spring" when walking over them.
Around here the steel "I" beam and 12 foot span 2x12 is back in favor because of this.

 

[csp]

Thanks. I saw those and I wish I had a Menards somewhere even remotely close to me so I could price those out and compare it to the other options.

If your location was listed in your profile someone reading this may be able to point to where you could look locally.

 

[b4z]

I have just modified our garage to remove a center support post and beef up the attic above.
It was 2 2x8s spanning 22' with a center support into the concrete floor and 2x6 floor/ceiling joists supporting the garage plaster ceiling and decking above for attic storage.
It is now 3 2x18" LVLs nailed together($1126) and the original 2x6s sitting on a 2x8 ledgers. When I sister 2x10s to the 2x6s for strength on the attic floor they will sit flush with the top of 2x18 LVLs. It will be super strong.
I'm going to agree with the other posters who have said that it is better to have a strong center spine and 2x10s or 12s off of that. I think it will be less expensive as well.
I am in charleston sc where will build for wind uplift and seismic. Mine was done by a engineer because it was required yours can probably be designed by the lumber yard.

BTW the plaster ceiling is so heavy the 11' 2x6s had deflected over a inch.

 

[b4z]

Everybody has been ignoring the issue of "stiffness" in the floor above.
Open web, and even some solid wood web "I" jousts have fallen out of favor because they just do not have a "sold" feel.
They do meet all the load bearing specs but people feel a flex or "spring" when walking over them.
Around here the steel "I" beam and 12 foot span 2x12 is back in favor because of this.

Agreed!

 

[Jon_E]

Open span in my 24' x 36' garage. I used (2) W14x30 spanning the full 24', between each garage bay, and each 12' bay has roughsawn (full dimension) 2x10 pine at 16" on center. According to my calculations it can handle 100 psf live load. I was going to use I-joists but they are really "bouncy" for a long span. I also considered floor trusses and the cost was prohibitive.