# Flooring for a new second floor shop



## Thrifty Tool Guy (Aug 23, 2007)

Hello,

I've recently had a second floor added to my detached garage for a woodworking shop. Interior dimensions are 21X22-ft with a ceiling height of 8 - 10-ft (scissor trusses). The floor joists span width of the garage width (21-ft) and are 14" high OSB laminate I-beams on 16" centers. At this point the second floor is only the ~1/2" thk OSB sub-floor, but it does seem strong. My carpenter friend thinks that a layer of painted Lauan board would be fine as a shop floor. Unfortunately, I have a rather low opinion of Lauan underlay and doubt that it will wear well. But, I might be wrong.

At this point, I'm seeking input on sturdy, durable and affordable options for this floor. Relative to equipment weight, the heaviest object will probably be a cabinet table saw (something like a Unisaw).

Thanks


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## RJM (Apr 11, 2010)

Thrifty Tool Guy said:


> Hello,
> 
> I've recently had a second floor added to my detached garage for a woodworking shop. Interior dimensions are 21X22-ft with a ceiling height of 8 - 10-ft (scissor trusses). The floor joists span width of the garage width (21-ft) and are 14" high OSB laminate I-beams on 16" centers. At this point the second floor is only the ~1/2" thk OSB sub-floor, but it does seem strong. My carpenter friend thinks that a layer of painted Lauan board would be fine as a shop floor. Unfortunately, I have a rather low opinion of Lauan underlay and doubt that it will wear well. But, I might be wrong.
> 
> ...


I agree with you and wouldn't use luan for beefing up a subfloor. It's a relatively weak softwood. I wood also want a floor thicker than 3/4". Also, this composite floor would be weaker than a single layer of 3/4" material (lots of construction adhesive could mitigate this).

If I were doing this, I would look into adding one of the following on top of your 1/2" OSB (my order of preference):
- 3/4" T&G plywood
- 5/8" T&G plywood
- 3/4" plywood
- 1/2" plywood
- 3/4" OSB
- 1/2" OSB

You will want to make sure you use construction adhesive between the 2 layers and a sealer/finish - especially for OSB. I'd probably use a clear urethane finish.

By the way, what do your local building codes require for subfloors?


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## bobj3 (Jan 17, 2006)

Hi Thrifty

I did the same thing on a add on room for my shop (8' x 22' ), I now have low spots  every 8" or so about a 3/8" to 5/8"" drops in the floor,the joists are just fine but the OSB did give under the weight.  now I need to take every thing out and put down some more OSB..with some screws...

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Thrifty Tool Guy said:


> Hello,
> 
> I've recently had a second floor added to my detached garage for a woodworking shop. Interior dimensions are 21X22-ft with a ceiling height of 8 - 10-ft (scissor trusses). The floor joists span width of the garage width (21-ft) and are 14" high OSB laminate I-beams on 16" centers. At this point the second floor is only the ~1/2" thk OSB sub-floor, but it does seem strong. My carpenter friend thinks that a layer of painted Lauan board would be fine as a shop floor. Unfortunately, I have a rather low opinion of Lauan underlay and doubt that it will wear well. But, I might be wrong.
> 
> ...


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## Hamlin (Dec 25, 2005)

Why place your heavy equipment up on a second floor? Sorry, this doesn't make any sense to me at all. T&G 3/4" ply is the way to go for your flooring. Better stability. I've seen a 1/4" hard board sheeting screwed & glued down on top of 3/4" ply as the final floor covering before. Works well. 

I do have to agree, check your local building codes first!!


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## BigJimAK (Mar 13, 2009)

"Relative to equipment weight, the heaviest object will probably be a cabinet table saw (something like a Unisaw)"

My Uni weighs in at 600+# (275 kilos). If I was going to be putting that and other (lighter but) heavy objects on a second story I'd pay $100 for an hour of a structural engineer's time (possibly the one who did your home, if you used one) to do a couple of quick calculations for you. First, that's a lot of weight in about a 2'x2' (approximate size of the base) area on the second floor and secondly the weight isn't distributed evenly over that area. It may be something simple, like placing an extra layer of ply directly under the saw or ??? With the mobility kit (like I have) my concern would be even more so, since the load is concentrated where the wheels touch the floor.

It'll probably be OK but the engineer may have some suggestions on which way to orient the tools to best distribute the load. 

My $0.02..


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## Thrifty Tool Guy (Aug 23, 2007)

Hamlin said:


> Why place your heavy equipment up on a second floor? Sorry, this doesn't make any sense to me at all.


Sometimes, up is the only option.


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## Hamlin (Dec 25, 2005)

Thrifty Tool Guy said:


> Sometimes, up is the only option.


I won't argue that. Doesn't mean I agree with it.  I do wish you the best of luck. 

I personally don't like the idea of having 1000's of lbs. of equipment sitting on top of my head in a garage just waiting for the right moment to decide to come down and "visit me when I least expect it". Plus, I know you'll never find me trying to lift or carry a TS to an upper level. Just placing mine on it's mobile base by myself was a real PITA. 

Building codes and a structural engineer as Jim mentioned is the best option to check in with first. In time, you'll still have area's to where they'll sag. No getting around that, unless you use concrete or steel flooring. Even casters on the bases over time, will get "flat spots" in them. It's that gravity thing we all love an hate. 

Cheers


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## Thrifty Tool Guy (Aug 23, 2007)

RJM60 said:


> I agree with you and wouldn't use luan for beefing up a subfloor. It's a relatively weak softwood. I wood also want a floor thicker than 3/4". Also, this composite floor would be weaker than a single layer of 3/4" material (lots of construction adhesive could mitigate this).
> 
> If I were doing this, I would look into adding one of the following on top of your 1/2" OSB (my order of preference):
> - 3/4" T&G plywood
> ...


Thanks for the info. Relative to local code (PA requires the UCC, state-wide), I'm good.

However, I do need to update the info I previously provided. The OSB I-beams are the Weyerheauser TJ-360 units (14" high, 2.5" wide x 1.5" thk ends) and the OSB floor sheeting is the 23/32" (18mm) Ilevel (tm) T&G product from Weyerheauser. So, I'm in better shape than indicated by my first post, but I'm still tending to adding an additional 1/2" of plywood. But, what type of plywood should it be to avoid voids in the laminations and have a good hard surface. I assume hardwood, but that's pretty pricey at this time.


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## RJM (Apr 11, 2010)

Thrifty Tool Guy said:


> Thanks for the info. Relative to local code (PA requires the UCC, state-wide), I'm good.
> 
> However, I do need to update the info I previously provided. The OSB I-beams are the Weyerheauser TJ-360 units (14" high, 2.5" wide x 1.5" thk ends) and the OSB floor sheeting is the 23/32" (18mm) Ilevel (tm) T&G product from Weyerheauser. So, I'm in better shape than indicated by my first post, but I'm still tending to adding an additional 1/2" of plywood. But, what type of plywood should it be to avoid voids in the laminations and have a good hard surface. I assume hardwood, but that's pretty pricey at this time.


This is why you should go with a product designed to be used on the floor. T&G subflooring does not require an underlay and can be used as is for the finished floor for your shop Idon't believe this product has any voids). Also, the material cost difference between 1/2 ply and 3/4 T&G is about $160. This is small compared to the added stiffness you would get.

I think you wood be happier in the long run if you spent the extra money now. Screws and construction adhesive will also add a lot to the strength of the floor and minimize/eliminate squeaks.


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## RStaron (Sep 25, 2009)

Just my 2 cents, thrifty. I would go with another layer of 5/8" Sturdy floor plywood, glued and screwed. And on the ceiling in the garage I would go with a double layer of a fire rated drywall, as if you ever have a fire in the lower or garage part the I- Joist will burn so quick and with the weight above, well I guess you know what will happen. I some of the Chicago suburbs many have code to this affect even above crawl spaces.Some things it doesn't pay to be too thrifty! Also the drywall on the underside will keep the I-Joist from twisting, Yes the do twist. It will also stiffen the whole floor system.


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## TRN_Diesel (Feb 24, 2009)

NOt sure what you have for cross bracing under the floor but it wil help big time. CAn you add a load bearing beam over the middle span to help take the weight? FOr sure though 3/4" T&G screwed and glued with PL400 glue.

Have you considered running your electrical in the sub floor to plug in your saw? Don't forget to add some plugs overhead as well. 

Dust collection to would be nice hidden in the floor. I hate tripping over my on the floor.


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## Thrifty Tool Guy (Aug 23, 2007)

RStaron said:


> Just my 2 cents, thrifty. I would go with another layer of 5/8" Sturdy floor plywood, glued and screwed. And on the ceiling in the garage I would go with a double layer of a fire rated drywall, as if you ever have a fire in the lower or garage part the I- Joist will burn so quick and with the weight above, well I guess you know what will happen. I some of the Chicago suburbs many have code to this affect even above crawl spaces.Some things it doesn't pay to be too thrifty! Also the drywall on the underside will keep the I-Joist from twisting, Yes the do twist. It will also stiffen the whole floor system.


You know, the biggest issue with using the 1/2 or 5/8" sturdy floor plywood is finding it. In my area, the 3/4" is the only available product.

Relative to the drywall, it's not required by code in my area and I want the below floor access for future work/modifications. However, I really like your point about preventing twist. What do you think of using 2-ft x 7-ft sheets of drywall or OSB glued and screwed to the first floor ceiling as shown in the attached figure.

Thanks


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## TRN_Diesel (Feb 24, 2009)

Thats a bit overkill. When I framed houses we just used 1x4 and nail them in. 

You could strap the ceiling and have the 1x4 line up to screw the drywall ceiling into. Or router out a grove for them to the depth so they sit flush.


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## Thrifty Tool Guy (Aug 23, 2007)

TRN_Diesel said:


> Thats a bit overkill. When I framed houses we just used 1x4 and nail them in.
> 
> You could strap the ceiling and have the 1x4 line up to screw the drywall ceiling into. Or router out a grove for them to the depth so they sit flush.


Dan,

Which piece is it that you want me to cut the groove in? 1x4 or the I-Beam?

Jon


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## TRN_Diesel (Feb 24, 2009)

The 1x4 needs to sit in a groove on the ceiling joist so you would have to rout the joists to allow them to sit flush. If you do it this way you can use the ceiling joist to screw on your drywall to the ceiling. I assume you want to cover the ceiling right? If not just strap the ceiling with 1x4 to stop the joist from twisting and maintain the spacing. Lay out the spacing on the 1x4 prior to installing it to help align the joist.


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## RJM (Apr 11, 2010)

*My "2 bits" on notching floor joists.*

Never ever, ever notch a floor joist, especially I-beam floor joists. This is often done but is not a good practice and will significantly reduce the load capacity of the joist. This is severly exacerbated in composite I-beams since the top and bottom flanges carry all the tensile and compressive loads in the beam. Cutting a 3/4" notch in a composite I-beam with 1-1/2 inch thick flanges will cut the load capacity of the beam up to half of it's rated capacity. Also, cutting a notch in the center of the span is the absolute worst place for a notch since bending loads are highest there.

There should already be sufficient cross bracing to prevent joist twist but it's not uncommon for it to be left out, even by some "professionals".

If it was my building, I would make sure solid blocking was installed rather than just cross bracing. Blocking should be the same height as the beam. Additional I-beam can be used for blocking. It's usually cut to the width of the gap between the flanges (leaving a gap between the perpendicular webs) but I've also seen it cutout to match the cross-section contour of the I-beams (eliminates the gap). I've also seen it cut to width and filler blocks added to the web (covers the gap). If It was mine, I'd cut it out to match the contour. More work but looks a lot better (I'm not sure it adds any strength but it definately does not make it weaker).

If "running your electrical in the sub floor" ws menat to mean cut a groove in the subfloor and lay in power lines, I say don't do it! It's illegal for obvious reasons. If i interpretted it wrong, I apologize. I think it's a great idea, however, to install power under the floor. Same with the DC. The only drawback to this (not counting cost, time, effort) is that once done, the layout is locked in. If you leave the joist exposed underneath, you can change the layout but you will need to plug up holes. Alternately (this is what I'd do) you could layout your shop with DC and power above the floor and once you've used it fo a while, you could add the power and "plumbing" under the floor. Remember - no notches, or holes, in the flanges. Holes in the webs should be in the center third of the web and not close together. There's detailed I-beam installation guides you can find on the web. Here's one.

Drywall offers no real strengthing and should not be depended on for stiffening. OSB would work but should not be needed with proper blocking. If fire is an issue, consider a sprinkler system. This could also reduce your insurance premium. 

Bottom line:
1. NEVER, EVER cut notches, or holes, in the flanges of I-beams (for that matter, never notch floor joists, beams, or studs).
2. Solid blocking is much better than 1x stapping, or cross bracing, to prevent joist racking.
3. NEVER, EVER install any utilities "IN" the subfloor (or for that matter, "in" wall or ceiling coverings).
4. Consider adding a sprinkler system for fire prevention.


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## tdublyou (Jan 8, 2010)

RJM60 said:


> Never ever, ever notch a floor joist, especially I-beam floor joists. This is often done but is not a good practice and will significantly reduce the load capacity of the joist. This is severly exacerbated in composite I-beams since the top and bottom flanges carry all the tensile and compressive loads in the beam. Cutting a 3/4" notch in a composite I-beam with 1-1/2 inch thick flanges will cut the load capacity of the beam up to half of it's rated capacity. Also, cutting a notch in the center of the span is the absolute worst place for a notch since bending loads are highest there.
> 
> There should already be sufficient cross bracing to prevent joist twist but it's not uncommon for it to be left out, even by some "professionals".
> 
> ...


 I have to 100% add +1 to Robert's points above.
A lot of things can happen when you notch framing members, and none of them are good, and his points on blocking are spot on.
As for running in floor wiring, there is a safe way to do this. Around where I live it used to be a very common practice to run electrical conduit between the sub floor and finished floor. 
After the sub floor is layed, 1 x 2 sleepers were nailed on top of and parallel to the joists and the conduit run in the void between the sleepers. Afterward the finish floor (usually hardwood) would be installed on top of the sleepers. Of course this makes future alterations more difficult, but it is definitely a clean looking method.


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## Thrifty Tool Guy (Aug 23, 2007)

Great info guys. Since I don't have a lot of i-beam scrap, I'm going to combine Dan and Roberts input and use my scrap joists above the strapping at "strategic" locations. Therefore, I need some input on how to attach the blocking to the joists.

Thanks,

Jon


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## RJM (Apr 11, 2010)

http://www.gp.com/build/DocumentViewer.aspx?repository=BP&elementid=4815

Look at page 7 - lower left


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## RStaron (Sep 25, 2009)

Thrifty Tool Guy said:


> You know, the biggest issue with using the 1/2 or 5/8" sturdy floor plywood is finding it. In my area, the 3/4" is the only available product.
> 
> Relative to the drywall, it's not required by code in my area and I want the below floor access for future work/modifications. However, I really like your point about preventing twist. What do you think of using 2-ft x 7-ft sheets of drywall or OSB glued and screwed to the first floor ceiling as shown in the attached figure.
> 
> Thanks


I'd go with the 1x4's nailed to the bottom of the I-Joists. About three rows evenly spaced. I used 11-7/8" I-Joists 18' long spaced 16" apart in my kitchen remodel and I get some bounce in the floor as I walk across. This is well within specs of the I-Joist, but I can't put down ceramic tile as I had planned with that bounce. I am going to put 1x4's on the bottoms to help stiffen them as my carpenter brother-in-law suggested. I was just concerned that the weight of your woodworking machines would cause the I-Joists to twist.


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## TRN_Diesel (Feb 24, 2009)

I agree with Ron 1x4 is easier and will provide you with necessary support to stop twisting. What did you space your TGI's at? Was it 24" o/c or 16" o/c. 

You may want to figure out the weight of everything and then check the load specs on the floor to see what your deflection would be. 

May sound weird but suspended ceiling underneath would allow you access to the ducting and electrical as well. Not sure what your ceiling height is but I am sure you will figure it out once you read all the imput you have gotten.


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## RJM (Apr 11, 2010)

TRN_Diesel said:


> I agree with Ron 1x4 is easier and will provide you with necessary support to stop twisting. What did you space your TGI's at? Was it 24" o/c or 16" o/c.
> 
> You may want to figure out the weight of everything and then check the load specs on the floor to see what your deflection would be.
> 
> May sound weird but suspended ceiling underneath would allow you access to the ducting and electrical as well. Not sure what your ceiling height is but I am sure you will figure it out once you read all the imput you have gotten.


 



RStaron said:


> I'd go with the 1x4's nailed to the bottom of the I-Joists. About three rows evenly spaced. I used 11-7/8" I-Joists 18' long spaced 16" apart in my kitchen remodel and I get some bounce in the floor as I walk across. This is well within specs of the I-Joist, but I can't put down ceramic tile as I had planned with that bounce. I am going to put 1x4's on the bottoms to help stiffen them as my carpenter brother-in-law suggested. I was just concerned that the weight of your woodworking machines would cause the I-Joists to twist.


 

Anything nailed to the top or botom of floor joists will not prevent racking. You must have some kind of cross bracing to form a triangular load path connecting the top of a floor joist to the bottom of the adjacent joists and vice versa. Without the triangular element, all you have is a box which can easily rack. Think truss bridges - every (vertical) closed section is a triangle. Solid blocking looks like your making another box but really the load path is thru the two diagonals on the blocking.

Any bounce in the floor is due to insufficient load carrying members - i.e. not enough floor joist. Often, building to code is adequate structurally but may result in undesireable results (e.g. bouncy floor). Adding material to the top and bottom of a bouncy floor will help stiffen it but very ineffciently. Adding more floor joists, or sistering the existing ones, will add much more stiffness. A center support beam will also add stiffness.


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