24' Span for Loft Build in New Shop

[malibucrew]

I'm planning to build a loft in my new shop 24' x 30' shop. I'm wanting to build a loft against the back wall that is 8' tall x 24' wide x 8' long. I'm planning to use 6"x6" posts with max back wall span of 12' apart anchored to base plate secured with red heads. I'll be using 2x12s for my headers (landing on the notched posts) and my joists with plywood floor. My question is I would like to span 24' on the front beam to avoid having a post in the middle of my shop and wanted to know if I could combine 3 2x12x24's to give enough strength to span that far. I've done the research and see that tjis (i joists) and lvl beams have span tables for this, but these are not available at any of my local lumber yards. I did talk to a structural engineer who told me that just 2 2x12x24s would work, but a few other posts have said otherwise. This loft will mainly be for household storage on the sides and I don't expect to put a significant amount of weight in the front middle, but still need it sturdy. See attached picture for the layout.

 

[CraigStu]

I'd do the three 2x12s at least. But that is simply a gut feeling and I'd probably do four.

 

[billconner]

I'm skeptical of 2x12s spanning 24'. Looking at span tables for ceiling joists with attic storage - 20 psf - no. 1s of a few species (Doug fir, SYO) 2x12s 12" on center will work. Sort of says 4 might work as a header but simpler to just span the 24' for entire 8'.

Really need an LVL...

 

[duneslider]

I used 3@ 2x12 for my 13' span. 24' is a long run.

You could add a steel plate and make a flitch but that usually ends up more expensive than just doing LVL's for the same thing. Most lumber yards will help size your beam and order you the LVL and drop it off in your driveway. A lot of the smaller yards don't keep LVL in the yard but a order is just a few days away.

 

[Pontiac787]

Pretty sure my garage was framed with 4 LVLs for a 26ish foot span. As mentioned above, check with your local lumber yard. You might be surprised on pricing and they’ll deliver.

 

[sjvicker]

It depends on your hobbies but if I was in your position I'd have your engineer spec this as a steel beam that you can handle up to 1k additional point load in the middle so you can add a trolley and a hoist.

Second to that, look at using a glue lam. If you can't get I-joists or LVL's at your local yards (not the big boxes) then you have to be able to get glue lams.

 

[billconner]

Anyway to shorten span with posts 3 or 4 feet from each end? No post in center.

 

[Hank11]

Look at this:

https://www.southernpine.com/wp-content/uploads/2023/09/207_HEADERSandBEAMS_1218L.pdf

Especially page 17 for your use.

If different wood, look for similar documents for that wood.

Also look for same on LVL type materials. (likely you will end up with this)

 

[dcg9381]

LVL or steel I beam would be my choice.

 

[billconner]

I am surprised you can get 24' 2x12s but not LVLs. Usually 24' lumber is harder for me to get.

 

[strutaeng]

It's all going to based on how much floor capacity you need. For 24' long beams, looks a 3 1/2 x 16 PSL may work. Either 1.8E or 2.0E. I'm assuming 40 psf live load and 10 psf dead load (pretty common, just framing and open structure below - no sheetrock)

The LVLs are pretty comparable to PSLs, and the widths are nice because they match when ganged up. So the equivalent ganged-up width should work.

Since you are using 6x6 columns, I would probably just use 5 1/4 x 16 PSL or the ganged up LVLs. Or just use 5 1/4 x 5 1/4 PSL posts to keep everything the same width. They are very nice and straight and much stronger than solid wood.

 

[Hank11]

If you are lifting by hand, ganged smaller pieces are lots easier to lift.

 

[billconner]

I'm assuming 40 psf live load and 10 psf dead

An attic is 20 psf, a bedroom 30 psf, and 40 psf for a living room. Based on the earlier posts I assumed attic loads or maybe bedroom and certainly not a living room which would support a crowd of people moving around. With less than head height, 40 seems overkill. On the other hand, if stacking boxes of books and paper, 40 isn't enough.

 

[MadScientist3019]

An attic is 20 psf, a bedroom 30 psf, and 40 psf for a living room. Based on the earlier posts I assumed attic loads or maybe bedroom and certainly not a living room which would support a crowd of people moving around. With less than head height, 40 seems overkill. On the other hand, if stacking boxes of books and paper, 40 isn't enough.

The other consideration is the deflection allowables. I would think the l/360 would be fine for storage where for active time spending in the area you may want l/480 for a stiffer floor.

 

[billconner]

That's a high standard. Iirc the IRC is 1/360 for living spaces 1/240 for roofs and attics. I would think a storage loft in a garage would be fine at 1/240. Maybe less if drywalling the underside.

 

[strutaeng]

An attic is 20 psf, a bedroom 30 psf, and 40 psf for a living room. Based on the earlier posts I assumed attic loads or maybe bedroom and certainly not a living room which would support a crowd of people moving around. With less than head height, 40 seems overkill. On the other hand, if stacking boxes of books and paper, 40 isn't enough.

Yeah, that's why I stated load since nobody had said anything about loading. OP should probably clarify what's he's intending.

All of the mezzanines I've designed have been in the 60 psf range, but for industrial use. 40 psf seems right for me, at the minimum. 20 psf is not much weight honestly for any kind of "floor." Always better to be on the conservative side, and he'll wind up with a much stiffer and solid-feeling floor. We've all been on top of roofs (20 psf live load for those) and hate that sping-y feel of the either the deck deflecting or the rafters. Or at least that's my experience...if you start talking floor vibrations, then you are in the L/480 deflection numbers or better.

Reading back, I see OP called it a "loft", not a mezzanine, so who know what's he's thinking...

 

[billconner]

Not disagreeing but I mentioned 20 psf in post 3. And I think it's a 14' high building so less than 5' above mezzanine. Felt like an attic load.

 

[strutaeng]

Not disagreeing but I mentioned 20 psf in post 3. And I think it's a 14' high building so less than 5' above mezzanine. Felt like an attic load.

Oh, you are correct. Sorry, I missed that

We probably won't hear from OP...he hasn't been seen since he joined and posted the question.

 

[NUTTSGT]

I am surprised you can get 24' 2x12s but not LVLs. Usually 24' lumber is harder for me to get.

That's what I was thinking. Almost sounds odd to me or a counter guy that doesn't want to make a phone call for a special order.

 

[billconner]

Did similar in grad school shop. Stressed skin. I think 20'. 2x8s with ply skins on both sides.

 

[Hank11]

Did similar in grad school shop. Stressed skin. I think 20'. 2x8s with ply skins on both sides.

I bet that was stiff!

 

[billconner]

I bet that was stiff!

Yeah. Stressed skin platforms are stiff.

 

[mdim]

Would go with an LVL.

Lumber yard certainly won't have it in stock, but it usually only takes a few minutes to order one (and get it delivered). You could probably patch something together with regular lumber but why?

 

[carlaisle]

Does the front of this "loft" need to be open or is it to be enclosed? If engineered lumber is not conveniently available, you could just make the front wall a truss.

 

[malibucrew]

Appreciate all of the feedback, I decided to just use the middle beam to make sure I was covered and adjusted my lumber according to span tables for a 40 psf live load. Again this is just for general attic storage for my tools and my wife's things, so not much weight up there. I did it all by myself over a 3 day weekend, very happy with how the results turned out

 

[FL Guy]

Appreciate all of the feedback, I decided to just use the middle beam to make sure I was covered and adjusted my lumber according to span tables for a 40 psf live load. Again this is just for general attic storage for my tools and my wife's things, so not much weight up there. I did it all by myself over a 3 day weekend, very happy with how the results turned out

Do,you have any other pictures?