Framing question-

[Foghorn]

I've got a 20x30 metal shop and I'm looking to add a small loft for storage.
My plan is to build it suspended from the existing framing, ie no legs. 20x10 is what I'm shooting for just based on the existing structure.
My question is the 20 ft span. Is a double 2x8 with a 3/4 plywood core gonna be strong enough? All glued and screwed of course. Not much weight planned to be up there, extra coolers, decoys and me ect.. just worried it might start sagging if I don't do it right.


Thx

Fog

Nothing screams poor craftsmanship like wrinkles in your duct tape

 

[1krr]

If you are doing it out of wood, they make engineered laminate beams in just about any length you could want. You might want to look into those.

 

[JoshGN]

Go to a lumber yard and talk to someone there...preferably an engineer, they will be able to help you more specifically...

I just did something similar but on a larger scale. 40ft across the front and 20ft deep...I used 16in I joists and 16in LVL across the 40ft span...

 

[761mph]

also take into account that the roof truss's might not be designed for the extra load of the loft and contents without some extra support legs

 

[doctorjj]

20 foot clear span will need more that 2x8. Glue lams are the way to go. Prob need two 2x12 glued and screwed together.

 

[TwoForFlinching]

2x8's aren't bad, but thats a long span. Even on the 12, it'll sag and flex with age/weight.

Spanning 20', look into engineered OSB i-beams. They're really freaking strong, but more flexible than wood. While it most likely won't ever sag, there will be a slight bounce.

Board beams are extremely strong and stout, but spanning 20', it's gonna cut into your headroom on either floor. They have to be thick.

Best of luck to you!

 

[DeeJay]

I covered the same span in my shop. I wanted to put a load bearing loft above a 20 ft section of my 20x40 building. This was in 2005 and do not recall what loading per square foot was used but more than you indicated. I ended up with 2x10 on 24 inch centers across the ceiling. However, this was from an outside stud wall to new stud wall in the center of the building. No way would I replace one of the 20 ft walls with a 20 foot 2x8 and plywood sandwich.

I did replace a load bearing wall down the center of an old house that I converted to a shop in 1997. I put plywood in between a pair of 2x12's and screwed them together - forgot to glue but don't know how much difference that made. I then started removing the sag in the roof line by adding braces to the ceiling trusses. Doing this started to load the center "beam". I only got 1/4 of the way from one end bracing the roof before the "beam" started to sag - a lot. My fix was to add a 2x10 to the each side of the beam since I did not want to tear the whole thing down.

I agree with others, get an engineered beam. They are very common and are used as headers on nearly all garage door openings nowadays.

 

[Foghorn]

Cool... thanks for the info. I'll check on getting one of them!

Nothing screams poor craftsmanship like wrinkles in your duct tape

 

[Mr.Glock]

also take into account that the roof truss's might not be designed for the extra load of the loft and contents without some extra support legs

Best listen to this post.

Those metal trusses in your "20x30 metal shop" are designed to support weight on top of them, they are not designed to support weight from the bottom. You need to support your loft with legs from the floor to carry the weight you plan on putting on your loft. I have seen metal trusses fold under from guys trying to pull engines off them, it makes for a expensive mess to have to strip off your roof/insulation to put on new trusses and re insulate and re skin.

As also stated above, you can support your span from both sides and keep your free span area of your shop if you do it right. You can run a engineered glue lamb from floor supports on each side of your loft.

 

[Boehlertaught]

I agree with using engineered beams. We just finished a new garage and spaned 27 feet with 12 inch beams on 12 inch centers. Wentere. Went a little big on the beams and used 12 inch centers because the upstairs is a gym with lots of exercise equipment. The floor doesn't shake at all.