Structural Engineer for Shop?

[Chen-Tin Tsai]

I am starting to outfit my new shop, which is in the second story of a 2-car detached garage on the property my wife and I purchased. The garage has a lot going for it: it's detached from the house, with nearly 9' ceilings on the first floor and mostly that on the second floor (away from the sloped roof areas on each side), has it's own 100 amp sub panel with ample space for additional circuits, and 2x10 on 16" center second floor structure with an I-beam in the middle. While I was planning on taking my time upgrading and outfitting the space, an impromptu purchase is making me accelerate my plans.

This is the impromptu purchase: a 1999 Powermatic 66 with a 5hp 3ph Baldor motor, 5hp static converter, long rails for the Accufence and mobile base from a fellow creeker.

Assembled in it's original home.

Disassembled in my garage.


Now, I'm in the process of preparing my second floor shop to receive this fine piece of machinery. I know I will definitely need to have a 230V electrical line installed so I can power it, and find some strong folks to help with the moving up the stairs. However, I'm wondering if I would need to bring in a structural engineer to inspect the structure to make sure that it will support the 600+ pounds that the Powermatic will weigh once it's assembled. Are there any other Creekers who went through outfitting a second story shop with any insights to share? Are there any structural engineers in Central Maryland on SMC?

[Brett Bobo]

Hi Chen-Tin,
Regardless of the application, a professional opinion is always worth having and more so in your situation. More importantly, it may be mandated if you're required to pull permits or submit plans/drawings for city or country approval. I don't know of a firm specifically in your area but try to find a residential engineering firm that does forensic inspections with licensed SE's on staff. Before doing so, get a good game plan of your equipment layout/locations so you can address all of the structural issues at once.

Having said that, posting pictures of the existing layout and planned layout helps tremendously in giving advice on what may or may not be possible. Assuming it's a standard width garage (~20' wide), my initial guess is that the existing framing might possibly be sized to accommodate a future second floor, i.e. other than attic storage, since you have a wide flange splitting the center of the garage.

[Mark Engel]

My shop is on a crawl space with the same floor configuration. The center beam of the floor is four 2x10 across the length (26') of the building with two evenly spaced concrete pillars under those. The floor joists are perpendicular to the main beam. The sub-floor is 3/4" Advantech. I did not put in a finish floor.

I currently have a Grizzly G0623 sliding table saw, a Grizzly G0453 15" planer, a Grizzly G0514 19" bandsaw, a Seco 3hp shaper, router table, work bench, assembly table... etc.
The floor has never even creaked. It feels nice and solid with no bounce.

Garage-Shop_023.JPG Garage-Shop_038.JPG Shop_setup_2-16-2013_1_.jpg Shop_setup_2-16-2013_3_.jpg

[Andrew Fleck]

2x10's 16" on center is plenty strong enough to hold that saw. Think of 4 or 5 people standing in a circle talking in your living room or the whole family sitting around the dinner table. It's easily the same weight.

[Jim Andrew]

What is the distance from the outside wall to the center of the wall? Maximum length of 2x10's on 16" centers used to be 16', haven't checked the code in 12 years. The maximum span was actually about 15'3", but you had the width of your foundation wall and the wall in the center, so you could build a 32' wide house with 2 x 10 @ 16" oc. If your garage is twenty some feet wide, with an I beam running down the center, you are much stronger than the code required a dozen years ago.

[Phil Thien]

I'm not an engineer. But if I were, I'd not only want to know the span of those 2x10's, I'd want to know the size of that I-beam (flange and web thicknesses and widths), and I'd want to know what is supporting the I-beam and where. I'd also need to know a little about the 1st-floor framing.

I agree that because it sounds like you may need some permits for electrical, you may want to consult the building inspector and ask him if he thinks the structure is sufficient. Phrase it this way: "If this was your garage, would you be worried about putting a 600 # saw like that on the 2nd floor?"

[Chen-Tin Tsai]

The joists span around 12' from the walls to the center support. I think it would be sufficient, but there's a bit of "bounce" when I'm doing some hard planing or chopping mortises (I'm still mostly a hand tool guy ) at my workbench. I'm not sure if it's due to the subfloor or the joists. So far, I'm leaning towards having it assessed by a structural engineer, if nothing else than for peace of mind. It's probably much easier to have that done now, before any upgraded wiring, insulation, drywall and floors go in.

Phil, when you say "consult the building inspector", are you referring to the inspector that works for the permit office in the county?

[Mike Olson]

2x10s spanning 12' should be fine, not sure why you have an existing bounce. Can you see the floor joist from below? I'd say get up there and inspect them.

Blocking between the joists helps with bouncing.
Also, look for knots on the bottom of the joists. Many builders don't know the Knots UP! rule I had hammered into my head back in the day. If there is a knot showing through the bottom of a joist or close to it, chances are it will crack right there and your left with a 2x6 or 2x4 strength.

[Chen-Tin Tsai]

Yes, I can see the floor joists from below; they're exposed and easy to take a look at. I'll take a look over the weekend. My suspicion is that the subfloor is 5/8" instead of 3/4", and rather old. I'm thinking about adding an additional layer of subfloor (perhaps the Advantech) over the existing subfloor.

[Phil Thien]

Phil, when you say "consult the building inspector", are you referring to the inspector that works for the permit office in the county?

Yep. They can be very helpful. I read a lot of online complaints about inspectors, but the vast majority of the ones I've run into are very helpful.

But if you don't mind spending money on an professional opinion, that would be even better.

[David Gutierrez]

Chen at 2x10 @ 16oc with 12' span will support about 80 pounds per square foot total load, assuming douglas fir larch #2. If the saw has a foot print of 30" x 30" or 6.25f of floor area and weighs 600 lbs then the live load is 96 pounds per square foot. you should also allow 10 PSF for dead load, the weight of the floor itself. the live load available is 70 PSF. You will be over the live load capacity by 37% that is too much. You should get a architect or engineer to take a look at this for you.
the other thing to consider is the floor itself 3/4 inch plywood subfloor may need some help depending on the finish floor.

[Chen-Tin Tsai]

I think that with the load being right at the limit, plus my future expansion plans (hard ducted DC, larger hand tool bench, project lumber storage, etc), I'll be bringing in a structural engineer to give me an evaluation and discuss options.

[David Gutierrez]

Chen
that is the best thing to do. An architect would also be able to help you with this. Who ever does it should check the joists, beam and subfloor.

[Brett Bobo]

Please, let's not confuse engineers with architects and vice versa as we are not one and the same.

[Mel Fulks]

Brett is right ,but that wasn't always so. Architects used to have to do their own engineering,the word means "chief builder" . Long history of architects staying on site and directing work. Benjamin Latrobe designed the masonry dome of the Philadelphia bank and personally showed the masons ,who had never built one ,exactly how he wanted it done. Top of it was 160 feet plus over floor. Separation of the two professions was a great thing for lawyers as around here they are always suing each other .