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.

[Brett Bobo]

Maximum length of 2x10's on 16" centers used to be 16'

Based on what area load? It's important that people don't use this as gospel and there's a significant difference in span length depending on the particular area load. Also, there's both strength and serviceability limit states to address. Being a structural engineer, I agree that yes, the table saw alone will likely not pose any issues but that's not to say that once a full shop is on the second floor that strengthening of the floor system may be necessary. In fact, it's likely that serviceability, i.e. deflection, will be the primary concern here based on the previously-mentioned "bounce" in the floor system.

[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.

[Chen-Tin Tsai]

Brett, based on your earlier post, I think my first step would be to consult a professional engineer first. At present, the garage is only rough framed, so all of the framing, supports, and subfloor of the second floor is visible. Would it be advisable to contact a structural engineer, or would there be other firms that does inspections/assessments of the situation?

[Brett Bobo]

Yeah, I think it's always good practice to seek the advice of a professional. Of course, this is assuming that you're not required to pull permits and submit stamped drawings for approval. Just double check the requirements.

As suggested previously, get a good game plan together of your proposed shop layout and possible future equipment so you can address hopefully all of the structural issues at once. Typically, the inspection firms will have SE's on staff for forensic work like this. There will likely be some independent SE's as well. It'll all depend on your area. For example, in Houston the structural framing plans are not required to be sealed, outside of the windstorm zones. It's merely a prescriptive code check via a city inspector, which can be reasonable for standard, residential construction.

The good news is that you have an open structure to make modifications, if necessary. There will be some complications with framing into the wide flange but depending on your capabilities, modifications are fairly straightforward.

[Jim German]

I'd say you'll be fine. 600lbs for the saw, plus 200lbs for you, 800lbs total spread over 3 2x10's on a 12' span isn't going to cause any issues. You're only looking at like 1/16th of inch deflection. The L/360 allowable deflection would be 0.4" so you have plenty of margin there.

Course if you are concerned with it, or are ever considering any really heavy tools you could always double up the 2x10s. If everything is all open already it'd be a cakewalk to do and not all that expensive.

As Phil mentioned though, if you're going to have a whole shop full of tools up there, the supporting I-Beam might be overloaded depending on how big it is.

[Bryan Rocker]

One thing you also need to be concerned with is the beam they are spanning on, 12' span would be ok if it were sitting on 3 2x12"s turned into a beam. I just went through some of this stuff this past summer when I had to have the sag in my garage fixed because the beam was WAY to small. For my 20x20' garage the load cals called for 3 2x16" glue lams installed to provide enough support. Was it a bit more than the min, yes but the code would be just a "Grade C" quality IMHO. You can figure out the designed loading via a few online sites, my current house has 2x10s over 3 2x12's in the middle spanning 12' ish and I would be concerned about putting my table saw in the middle, over the beam itself no but in the middle yes....way to much bounce and flexing. You will have a difficult time keeping your table saw level and true with all that flexing....

As with all things your mileage may vary and all men have opinions :0

I would recommend an engineer/architect....

Bryan

PS If I wanted to see this much snow I would have moved back to Nebraska......