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walkereng
walkereng, Consultant
Category: Structural Engineering
Satisfied Customers: 2596
Experience:  Over 30 years of Structural Engineering experience.
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I have put up a room in the corner of my detached metal shop

Customer Question

I have put up a room in the corner of my detached metal shop building with concrete floor. What center-to-center spacing would I need for my 2 x 6" joists (on metal hangers) across this 12' by 12' room where the joists are covered on top by 5/8" thick multi-layered plywood in orderto support 40 psf (pounds per square ft.) of random stuff being stored on top of that plywood?
Submitted: 4 months ago.
Category: Structural Engineering
Expert:  walkereng replied 4 months ago.

I can help

Expert:  walkereng replied 4 months ago.

What species of lumber will you be able to get?

Can I get back with you in about an hour or two?

Expert:  walkereng replied 4 months ago.

I’d like to point out that a Professional Engineer’s standard of care typically includes a site visit to assess field conditions and get an overall understanding of the structure. This can obviously not be accomplished through the internet. The information provided here is meant for planning purposes only (general sizing and budgeting) and is based on the information provided by you. All loading cases considered are for vertical loads only, no lateral analysis has been completed. The information should be verified by a professional engineer who can visit the site to ensure that potentially important information has not been overlooked or omitted.

For a 12' clear span and a Live Load of 40 psf and a Dead Load of 10 psf, you can use the following:

2"x6" (#2 grade) spaced at 6" o.c. (you can use Douglas Fir, Southern Pine, or SPF lumber)

Expert:  walkereng replied 4 months ago.

You will need to have a local engineer detail your connections, size your support, determine foundation requirements, and check your structure’s lateral stability.

If you feel you have received a satisfactory answer to your question, click the Rating button that is appropriate. Experts are credited for each adequately Rated answer they provide. If you have additional questions, please let me know. Thanks

Customer: replied 4 months ago.
This 6" o.c. takes into account the 5/8" thick plywood screwed into the joists, right? The concern here is only for stagnant storage of random objects on the plywood. The joists are suspended using metal hangers on 2 x 4 walls using 16" o.c. frames. These walls are sitting on high strength concrete (4000+ psf).
Expert:  walkereng replied 4 months ago.

If you reduced your Live Load from 40 psf to 20 psf for random light storage, you could use the following:

2"x6" (#2 grade) spaced at 12" o.c. (you can use Douglas Fir, Southern Pine, or SPF lumber)

Hope this helps.

Let me know if you have any more questions.

Expert:  walkereng replied 4 months ago.

If you feel you have received a satisfactory answer to your question, click the Rating button that is appropriate. Experts are credited for each adequately Rated answer they provide. If you have additional questions, please let me know. Thanks

Customer: replied 4 months ago.
As I originally said, I am storing random items, long-term, which I guess is dead load, right? I know the county building dept. said I needed my "attic" to support 40 psf, which they said is the minimal strength required for storage. They said they COULD have applied what is considered a more normal requirement of 120 psf. They felt I needed 4" o.c., but admitted that they didn't take the thickness of the plywood into account. Were they talking "live load" or "dead load" do you think (when they said 40 psf) AND did YOU take the thickness of the plywood into account? They're the people (in the building permit dept.) I'm trying to satisfy.
Expert:  walkereng replied 4 months ago.

Live Loads are any moveable load, so your storage would be Live Load. Dead Load is from the materials used to construct your structure.

I am going to attach a couple of files, both from the Building Code.

One is Live Loading for Residential occupancies and the other is Live Loading for Commercial occupancies.

Expert:  walkereng replied 4 months ago.

Here is the Commercial Live Load information.

Expert:  walkereng replied 4 months ago.

So the Live Loading will depend on if this is a Commercial or Residential occupancy

Expert:  walkereng replied 4 months ago.

The 40 psf is Live Load

The thickness of the plywood would be Dead Load and would not increase the load capacity of the floor joists. It would laterally brace the joists.

Expert:  walkereng replied 4 months ago.

Take a look at my information and let me know if you have any questions.

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