Floor joist spacing question

[Bo Montague]

Hello folks, new here and couldn’t find an answer in the search. I’m building a 20x26 shop, wood floor, 2x10 PT floor joists with 1 1/8” advantech flooring. Max span of 2x10’s is 9’6”. Load will be of a typical wood working shop, heaviest items will be a lathe and table saw. Floor will be beefed up under the lathe.

Here’s my question. Will the floor joists 24” OC be sturdy enough?

Thanks, Bo

[Matt Day]

I bet a structural engineer would know. Do you want a bunch of armchair woodworkers telling you the spacing or an engineer who will know what the inspector is going to be looking for?

[Paul Lawrence]

... Do you want a bunch of armchair woodworkers telling you the spacing or an engineer who will know what the inspector is going to be looking for?

Hey! I resemble that remark! :D

What are these 2x10s sitting on? You can decrease the span distance by putting a support in the middle, for instance.

There are plenty of tables on span distances for various size lumber available to a search.

[Scott Winners]

I am not an engineer. I have been on two different 2x10 floors. One with single layer TG 3/4 ply subfloor and 24" joist spacing, the other 16" joist spacing with two layers of 3/4" not tongue and groove.

both met code, the 16 center floor was a LOT stiffer.

I have never heard of advantech flooring before.

How much, while we are waiting for a structural engineer to come along, are you willing to have your floor bounce?

[Tom M King]

I wouldn't try to save a couple of hundred dollars by using 24", instead of 16".

[Tony Pisano]

I agree with the shorter span. You never know what fantastic deal you might get on a heavy piece of equipment in the future.

[Von Bickley]

I don't like 24" centers on rafters, studs or floor joists. I would spend the extra money and go 16" on center.

[Bo Montague]

Thanks for the response guys!
Matt - I’m sure a SE would know the answer, he’d also like a big check for the answer.
Paul - I’ve read span tables until my eyes blead, they say it can be done, was checking to see if anyone else had experience.
Scott - it’s good stuff, check it out http://www.huberwood.com/advantech/products/advantech-flooring
Tom - gotta save the money for that next piece of equipment
Tony - winning response! Never know when that deal will happen.
Von - gonna spend the extra for 16OC

Thanks again guys!

[Paolo Trevisan]

well... I am a SE and here is what I would do.
run a beam at mid span so now your joists are only running 10'
place joist @ 16 IN c/c. last thing you want is vibration on your floor.
with running machines you will get some vibration. yiu want your floor as stiff as possible.
3/4 in subflooring or EQ.
insulation between joists. and possibly run your dust collection ducting there as well.
you will not regret it. with lumber pricing as it is skimping to save 50 bucks isnt worth the potential issues later.

cheers. and enjoy the build.

lastly keep in mind the span span rating for the joists you are seeing is possibly not what the loading is for a shop floor.

p

[Lee Schierer]

Your cost difference will be about 12 joists for the 16 OC floor. The benefit is a much stiffer floor. You might also want to consider 2 x12's for your almost 10 foot span.

[Tony Latham]

I can't answer your joist question but I'm sipping coffee over the same Advantech subfloor. It's great stuff. Stiff.

You might also look at BCI engineered joists. They may be cheaper. https://www.bc.com/manufacturing/bci-joists/

For whatever reason, my house architect and contractor both agreed on them.

T

[Jim Becker]

I agree about looking at the engineered I-joists. My shop building was build with them in the ceiling of the first floor and the upper level is rock steady, even with just a layer of 3/4" plywood. (12" I-joists, 16" OC) I would imagine them combined with the Advantech would provide a shop floor you couldn't move with anything less than an earthquake. :D

[Todd Mason-Darnell]

You should be fine.

Max span, per the American Wood Council span calculator, is 15' 2"

https://www.awc.org/codes-standards/calculators-software/spancalc

That being said, I would go 16" OC for the stiffness.

[Jon Snider]

My floor in my shop in progress is 40 x 28’, with an approx 32’ metal I beam spanning the length down the middle on two 6’ concrete buttress walls, also sitting on two metal columns equidistant from buttresses.

The engineered floor I joists are 3” x 11 7/8” on 12” center, supported in the center by the metal beam. Wood flooring is 1.125” Advantech T&G.

This is was designed by an engineer after I gave him weights for some of my heaviest machines (up to 2500#) and locations. And then I told him I wanted to sleep better at night. Probably major overbuild but better than a collapsed floor for not a whole lot more money.

If I ever sell the house, I can probably call it a garage and park cars on it too.

Jon

[David M Peters]

Bo, can you describe your reinforced floor area for your lathe?

Some day I would also like to have a wood-floored shop but would almost want a separate concrete pad for my AB!

[Jim Andrew]

There is another choice. You can add one joist per 8' and go with 19" oc, or go with 16" oc and it adds 2 joists per 8'. Either are stronger than the building code for a house, considering you are looking at less than a 10' span on a 2x10. When I started my building career in 1976, you could go with a 2x10 16' at 16" oc. Still have the '76 code book. Your treated yellow pine is a stronger lumber than the typical HemFir we used in those days.

[Peter Christensen]

My shop has 2 x 10’s on one foot centers with 1” OSB. When I find some hardwood flooring on close out I’ll put that on too. My joists span about 16’ and 12’ supported by a LVL beam. I don’t at this time have any machines approaching 1000 pounds. When I get a pile of wood I lay it across the joists close to the wall or over the supporting beam below.

[Jerry Olexa]

A support in the center would help a lot....2 X10 would then work but I'd go 16" centers for stiffness for tool/machinery..I personally would go 2 X 12s also but I tend to overkill/overbuild. Remember too, later you may want to move machinery to new location in your shop so I'd build it strong everywhere.. Just my thoughts.

[Tom M King]

There is another choice. You can add one joist per 8' and go with 19" oc, or go with 16" oc and it adds 2 joists per 8'. Either are stronger than the building code for a house, considering you are looking at less than a 10' span on a 2x10. When I started my building career in 1976, you could go with a 2x10 16' at 16" oc. Still have the '76 code book. Your treated yellow pine is a stronger lumber than the typical HemFir we used in those days.

The little diamonds on tape measures are for 19.3 inches on center. It's hard to find insulation rolls for that spacing though, so not worth the few dollars saved.

[Frank Pratt]

I agree with Jerry. Beefing up the floor structure where you think your heavy machinery will sit just confines you to the initial layout. I doubt if you'll find many shops that have stuck with way the layout was originally planned.

[Chris Stolicky]

I built mine with 2x10's 16" OC. The span is <8'. I did beef it up under the lathe. Floor is 3/4" Advantech plus 3/4 oak flooring. Everything is solid. I would not not recommend 24" OC for any floor where you will likely have heavy machinery. Good luck.

[Frank Pratt]

I wouldn't recommend 24" centers on any floor, even with 1" subfloor & 3/4" hardwood. Especially in a shop.

[andy bessette]

I would go 12" centers for my own shop.

[Frank Pratt]

I would go 12" centers for my own shop.

Same here.

[Tom Bender]

If it was your money I'd go with 2 x 12s on 6" centers and marble over double diagonal hardwood planking.

[Peter Christensen]

Marble looks nicer but Granite wears better. ;)

[peter gagliardi]

In a shop floor, stay far away from I joists.
Stick with solid lumber, there is much less bounce, and it is ultimately stronger.
I know the engineering papers might argue differently, but all you have to do is walk/bounce on the two types, you will know immediately.
And 16” is the maximum center to center. If you see bigger or more machines in the future, go 12” on center.

[Jim Becker]

It's interesting you say that, Peter...I have zero bounce on my second floor of the shop even if I jump up and down. (I weigh just north of 200 lbs) It's only 3/4" plywood over 12" I-joists, 16"OC.

[Tony Latham]

My house is built with BCI I joists set 16" OC with a pony wall halfway across the 32' span. It's topped with 1" Advantec flooring and there is no bounce.

T

[Frank Pratt]

In a shop floor, stay far away from I joists.
Stick with solid lumber, there is much less bounce, and it is ultimately stronger.
I know the engineering papers might argue differently, but all you have to do is walk/bounce on the two types, you will know immediately.

Are you saying size for size, dimensional is going to be stiffer and stronger that I joists? Sorry, but that's wrong on both counts. And there is engineering to back that up. I did some pretty thorough research when I built my house & used I joists. 3 x 12 I joists on 16" centers with an 18' span, 3/4" OSB & 3/4" white oak flooring. It's very stiff.

About the only advantage dimensional has is that it will take longer to burn through in a fire.

[peter gagliardi]

Trust me, there is bounce.
I build houses for a living. You cannot detect bounce by yourself very easily.
Go to the middle of those spans with another adult, have them jump, report back.
I try not to use them, but every job I have visited that does, exhibits the same. These are installed per engineers specs.
Solid lumber does not do it nearly as much.

[peter gagliardi]

Frank, I am not convinced. The engineering used is mostly only to cover deflection- span cannot deflect more than 1/480 . The I joist will ultimately fail under less deflection than solid lumber, they are not good in fires, and they do not take shock load well at all.
Oh, and I forgot, they do not do point or concentrated loads well at all.

Solid lumber is forgiving- yes it will deflect more, but catastrophic failures are less frequent beyond the specs.
Engineers are smarter than me, so who am I to argue.

[Steve Milito]

Hello folks, new here and couldn’t find an answer in the search. I’m building a 20x26 shop, wood floor, 2x10 PT floor joists with 1 1/8” advantech flooring. Max span of 2x10’s is 9’6”. Load will be of a typical wood working shop, heaviest items will be a lathe and table saw. Floor will be beefed up under the lathe.

Here’s my question. Will the floor joists 24” OC be sturdy enough?

Thanks, Bo

I started with an on-line "barn" plan when I designed my shop but wanted to have it modified in a significant way; it was 40'x35'. My builder recommended a local engineer, who I used. His approach was "I can make this like a factory but it's going to cost a lot or you can put it on slab. We then went through the whole what's going in it conversation and I basically gave him a list of dream equipment (a full sized lathe, full sized sliding table saw, etc). What we came up with as middle ground was 2x12's on 16" centers and 12' spans. We also used 1 1/8 advantech flooring. There's a system of piers and girders underneath to support it all which is every bit as important as the joist spacing. I believe that live load rating was in excess of 175 lbs/ft^2. I hope that helps.