Hi All,
Looks like my wife has finally had enough of the mountains of dust in the garage and is close to approving a building for me and my tools. The idea is a 20 x 24 structure with a crawl space under and 10 ceilings.
Here’s my question….
The way and place I have to build it requires a not concrete floor. The floor will be regular joisting with a skin on top. I have lots of latitude on the joisting (engineered or just dimensional lumber) but wanted to know what you all thought about the skin.
Do any of you have just a plywood floor over joists? What about OSB? Thickness of floor? 16″ joist spacing ok? Do I need to double up the skin? Etc….
I am wondering if the weight of the tools requires anything special in regard to the floor structure so I can plan for it now and see how much it will cost.
Any comments would be greatly appreciated.
Thanks
Rob Kress
Replies
I'm certainly not a construction engineer, but it seems to me that a shop produces fairly high concentrations of weight on relative small footprints. How much so depends on the machines you have, or plan to acquire in the future, I'd think. As such, I'd lean toward keeping the joist spacing to standard, but using two-by sub-flooring with two layers of "skin" on top. OSB with plywood on top might be the way to go, but there are other minds here who likely have real knowledge on the matter.
A couple of things.
I would assume that the structure will (joists) will go in the 20' direction and that there will be an intremediate support. So the unsupported span will be 10'.
If this is the case and you expect to have heavy machines, 500 lb table saw, etc. then I would use joists at least 12" deep and perhaps double up on all of them. With the concentration of weight on say 3/4" skin it is possible with vibration and movement that the skin may fail.
I would use at least 2 layers of skin.
ASK
A 20-0 span is a longish span for wood. You will be using engineered trusses (I joist) of some sort. I would not shoot for the maximum spacing of the joist and you might even want or need to space them 12" o.c. Tongue and groove 3/4 plywood on the surface glued and screwed will work. I would not use OSB as it is rougher, will expand if wet and never compress again. Of course you could always split the span cross wise w/ a 20 ft beam or foundation wall below and reduce the span to 12 ft.
You will be asked about loads which will be called out by code. A normal floor load for a house has a 40 lbs per square ft live load required but I'm guessing that a shop would require a floor load of 120 lbs . You should talk with your local building official (inspector) about how shop will be classified. I think it would be considered a light manufacturing area. That will also tell you what loads you need to meet, fire resistive construction and set backs to property and other buildings.
It would be worth a couple hundred bucks to hire an engineer to do calculations for you and tell you how the floor should be built. If not that, then go to the lumber dealer, or call the rep at Louisiana Pacific and ask him what size "I" joist you will need at what spacing. He will ask you about the "live load" how stiff you want your floor, a matter of how much length divided by 240, 360 or 480 will deflect if loaded. An L/480 floor could deflect 1/2" when loaded. Is that acceptable? Long spans can get springy and you are dealing with a longish span.
Simple buildings sometimes aren't that simple. Talk with the local planning office. All those nasty rules have a purpose, just like the joints in wood working.
You may wish to take advice given here with a grain (OK, maybe a whole shaker) of salt, but if you have normal shop tools (as in hobbiest-type and not old "big iron"), standard construction should suffice. That's 2"X10" (or maybe even 2"x12") @ 16" OC (10' spans), with 3/4" subfloor (I'd use T&G plywood) and 1/2" or 3/4" finish floor.
As a reality check, I'd note that many appliances, etc. -- for example a loaded refrigerator or a loaded bookshelf -- outweigh pretty much any tool in my own shop, and standard flooring specs haven't failed me yet. ;-)
You may also want to post this Q over at Breaktime to get the builders' perspective.
Mike Hennessy
Pittsburgh, PA
Everything fits, until you put glue on it.
Edited 8/17/2009 12:16 pm ET by MikeHennessy
Edited 8/17/2009 12:17 pm ET by MikeHennessy
Rob,
I have about the same sized shop myself. Since you're already incorportating a crawl space you might want to think about some storage in it if you have the height also if you dry any lumber might be a good location, just be sure to get the soil treated. If I was going to place some of my heavier pieces over a framed in floor system i would first layout my machinery and then place a set of piers to support the additional load. A concrete pad say 12" thick by 16" square with a beam under the machine with a 6x6 post at the corners will surely support my 450 lbs tablesaw. I would place my joist on 12" centers with tongue and groove 3/4 plywood. The depth of the pad will be determined by local code and what bearing the soil in your area will bear. I live in the southeast and have no problem with this type of foundation on the commerical projects that I build.
StephanC
Guys,Thanks for the input. Here's a little more detail.....I built my own house. I have gone through the building process with the building department in my city and know the folks and how they operate. I will of course be talking to them.I do plan to split the 20' span in half so that my joist span is only 10'. I will probably be using an engineered joist because I want the floor construction to be more uniform than I was able to achieve in my house with dimensional lumber. I believe 16" o.c. is sufficient as well.Really my only concern is the skin and whether or not I need to double the skin or use something thicker or other than regular 3/4" t&g plywood. I have a lot of flexibility in how I build it but of course I don't want to over do it and blow the budget.I wonder what the cost of 2x10 spf would be for the flooring??Thanks for all the advice. Keep it coming if you have more.Rob Kress
Rob,To be code compliant you will probably have to use 3/4 inch plywood or OSB decking so you won't have a choice. A second layer won't be needed even if you don't put anything on top of it. 2x6 T+G spruce would make an excellent finished floor for a shop, and is readily available. It will get beat up over time though. Wider boards will have more problems with shrinkage and warping. There will be no need to go below 16" joist spacing and you might find it more economical to use 24" spacing with a slightly deeper joist which would allow for more insulation. Any competent designer could tell you in 5 minutes what your options are, this was all figured out a long time ago. John White
Shop Manager for FWW Magazine, 1998-2007
Although you have built a house you are not building a house. Numbers of loads quoted in one section for houses may not apply to what you are doing. Your work will probably be covered by the International Building Code not the International Residential Code. Under the IBC table 1607,1 calling out the required live loads the most likely fit would be light manufacturing at 120 psf. You are contemplating using relatively heavy pieces of equipment that place point loads not anticipated in residential construction. In areas where you plan to store stacks of wood why not plan on accommodating the loads? Live loads of 120 lbs per sq. ft must have the dead load of 10 to 15 lbs per sq ft. added to it to arrive at the total design load. That's why a lot of the tables for residential members use 50 psf or 40 psf live load and 10 psf dead load.Structurally speaking heavy girder members make the short spans and lighter joist make the long span. If you are placing a beam to split the span of joist you would want to make it as short as possible or across the 20-0 span. The difference between 10' joist spans and 12' spans is not even a factor if you're using engineered joist.I would not go 19.2 or 24" o.c. as the loads will cause the decking to have to be thicker. You wouldn't save much in materials with fewer deeper joist and heavier deck. And I agree that 3/4" plywood glued and screwed to the joist at 16" o.c. will probably work for a long time. I think they even make heavier sub floor material.My advise is to do what you and the magazine editor might consider overbuilding of the structure. Even placing joist at 12" o.c. is worth thinking about with thinner joist and deck. Good luck.
If this is on the same lot, and of non-commercial use so that it's use is incidental to the residence, then it is more likely to be an accessory structure (Section R202 definition) under the IRC, and not call forth requirements of the IBC for light manufacturing. But this is likely a call for the local building inspector. Let him sign off ahead of time, NOT while rejecting construction.
If you start building a commercial building you can end up with a major can of worms, as one thread here some time past testified. The builder of a one man shop had to have automatic dust collection turn-ons and explosion hazard equipment because some inspectors decided that any woodworking shop was a "dust hazard" area and needed to be treated like a flour mill.
It would also be more likely to be a zoning issue in many areas. That could be a tougher nut to crack--it would be around here in CT.
I know we may think so, but is a woodworking shop by definition "customarily accessory to and incidental to that of the dwelling"? Trying to convince an inspector or a board of zoning appeals of this fact, could bring a grim crooked smile to your face.My point is not that he is building a commercial structure, but that it's use, when trying to figure out loads, is most similar to light manufacturing. If that is the case, why not apply that knowledge? Yes, accessory structures on any lot can be a can of worms in trying to conform to zoning ordinances. I think we agree that it is best to understand them ahead of time before you've poured the footings and upset your neighbors. And out of curiosity, does anyone know of a dust explosion in a small wood shop?
Light manufacturing involves considerations (think fork lifts and the like) that just don't apply for what is essentially a garage shop. You can build a garage with the floor spec'd to 50 lb. per square foot, for example, only a bit more than the 40 psf for non-sleeping residential spaces. Now I wouldn't recommend going with code minimum--a little overbuilding is fine. A solid floor is a good thing, but if building officials get the wrong idea you could get way more requirements than would be necessary.
If you can't convince the building and zoning officials that the building is a customary accessory and incidental to the dwelling, then no matter how you spec the building you likely won't be able to build it next to your house, so lets not put bad thoughts in their heads. Starting off to build a "light manufacturing" spec'd building will send up the red flag real quick.
By the way, I have seen a local zoning ordinance somewhere that did specify woodworking businesses as a "customary home occupation." It isn't always so designated.
I can't find it in search, perhaps it was elsewhere, but I remember a long thread about the hoops a building inspector (supported by appeal to State building code authorities) put through a fellow building a one man (commercial) shop. It cost him many thousands of extra building expense and complication, for a hazard of very doubtful validity. It was very sad.
It's free advice. I don't think designing a floor system to meet it's need (particularly if you don't draw attention to it) will set off any red flags to a plan checker or building inspector. If they think you are overbuilding they will just smile. As one inspector told me, if it exceeds code requirements, we'll never ask you to less. The cost differential to go from your minimums using a 9 1/2" LPI 32 @ 16" o.c. to a 12" LPI 32 joist is about 5 percent. To go to a 14" LPI 32 would be a 20 percent increase over the 9 1/2 joist.. It is a balancing act if the 5 extra joist 12" joist need to hit a 12" spacing might be more cost effective. These costs even at 20 percent increase become lost in the total project costs. Why not do it right.If you were designing a commercial cabinet shop wouldn't you engineer the floor loads for light manufacturing whether they used a fork lift or not? What is the difference between a large commercial cabinet shop and modest home shop other than size? We often shoot from the hip and think you don't really need to do that. We know cars are heavier than people so if it holds up a car, it'll be fine. Except code requires a restaurant to have a 100 psf live load and a passenger garage requires only 40 psf. My advice is to have plans, talk with your city about the plans and do not build a wood floor for a woodworking shop to residential minimums. You just don't know when someone gets carried away and unloads a pickup truck full of lumber into the shop stacking it high and carefully parallel to the joist. But you know what they say about free advice. So hire an engineer.
In Humboldt Co., CA, a one-man shop at a residence can get around the zoning problem by being classified a 'cottage industry'. They want no employees, and very, very little customer traffic, deliveries and noise. It's a way to get a business license, if you really want one.Brian
Rob,
There is no need to over engineer this, as some are urging. Conventional light construction framing, designed to code is designed to support 50 pounds or more per square foot so any one 6' by 6' section of floor would be able to support almost a ton. Unless you intend to put all of your large tools in a big pile in the middle of the room you don't need any special flooring or framing.
The choices you make will depend more on budget, climate, foundation type, and a half dozen other factors.
John White
Shop Manager for FWW Magazine, 1998-2007
Rob,
If it were me, I would lay down 2x6 T&G glued and screwed to the joists and then screw down 3/4" Advantek T&G OSB over that. Keeping dust and dirt out of the grooves in the 2x6's will be a pain if it's on top. This would give a very stiff floor, particularly with an I-joist spanning just 10'. That said, for better feedback on this subject go to Breaktime where they do this for a living everyday.
You can use engineered lumber or 2x12 on 16" centers. Either way is fine. My shop is 20x30 with engineered 12" joists with a beam down the middle in a crawl space. So the unsupported span is less than 10'-0". I glued and nailed 3/4" osb.I would use Advantec if I were to do it again. I had never heard of Advantec at the time I built the shop. Later after using the shop for a few months I decided to put a finish floor down. Osb is a pita to sweep or keep clean. I stapled 1/4 plywood underlayment down and then installed the cheapest vynil flooring I could find. I found a peel and stick parquet flooring for .21 per foot. I had hoped it would last a couple of years until I had the funds to put down a better floor. This is the 12th year it'e been down and is still serviceable. Actually a lot of the floor looks fairly new, except where paint, solder, etc have stained the floor.
No need to double the floor , or go to any unusal lengths to frame it.If you plan to heat or air condition the shop, make sure you insulate it well. One other tip, 1/2" osb or plywood make a great interior wall sheathing. Osb looks rustic, I have the smooth side in and never painted it. I got shelves,jigs, saw blsdes and anything else you can think of hanging off the walls.No need for blocking, just a nail or screw .
mike
Wow guys,Thanks for all of the feedback. From what you've all said, it sounds like this floor is not really too big a deal. Great!I think that I would prefer osb with some sort of a finish floor (cheap and easy and strong). Perhaps really scrap t&g flooring from a local mill. My situation is a little complicated though by my wish to have radiant floor heating. Plus I have been considering building out of sips (so the many rodents living in my forest don't make a home in my walls). And in that case I could also use sips for the floor (with appropriate sub structure).Lots of options and really digging in now.Thanks againRob KressP.S. Anyone know how I can encourage a big snake to move in near my tree line? Or maybe a big owl or two....
Rob,
Oh well somebody's gotta throw a wrench inta the works. Is this building forever going to be a woodshop? Will it fit into the overall landscape of your property in terms of resale down the road?
I'm sure you have a lot invested in your property; wouldn't want to decrease its potential.
Sorry, I had to say it,Bob @ Kidderville Acres
A Woodworkers mind should be the sharpest tool in the shop!
Bob,That is one of the big considerations that my wife and I are mulling over. We are really fortunate to have the circumstance that we have..... great family and great careers (my wife really is my sugar mama). So when I was out of work a few years ago, we found this great lot and I built a really great house. In that regard, our house is on a small cul-de-sac street separated, but part of, a really fancy McMansion subdivision. Most houses in the development do not have such a big accessory building structure on their property but most houses have something. Also, my house is on one of the best pieces of land in the development and from the outside looks like one of the premier homes. Most people in our neighborhood have toys and we believe that potential buyers would appreciate a place to put their toys (jet skis, motorcycle, etc... NOT CARS) if we had to sell. And we are going to build this thing so that it looks like the house. All that said, we are trying to minimize the cost of the structure cause you never really know what potential buyers might like or not like. So we don't want to potentially throw away money on a really fancy building that detracts from resale.Rob
Let me throw a new material into the discussion: particle board. I'm not a fan of plywood for shop floors as the top ply is really thin and a mess if it is damaged by a falling object.Particle board is a less expensive version of MDF. (The particles are just a little larger; not dust as in MDF.) The very slight surface texture helps make it slip-proof and (I think) it is good looking. I would guess that a 1/2" overlayment would give you the surface and stiffness you want.Sorry to add one more branch to your 'decision tree'.Frosty"I sometimes think we consider the good fortune of the early bird and overlook the bad fortune of the early worm." FDR - 1922
Let me suggest you look at an Advantech type OSB. Not damaged by water in the same way as ordinary OSB. I believe it comes in an 1 1/4" thickness designed for solid subfloors.
In a McMansion subdivision, you might also think about a free-standing covered breezeway between the house and the shop. Just be sure it's wide enough to accommodate the inspirational bronze and marble statues along the path. ;-)
Surpisingly, there are no statues or marble fountains in the neighborhood. To tell the truth, I have found my neighbors to be very cheap with slightly entitled attitudes. These are all the people who spend all they have on nice cars and house not reserving anything in the bank for the rainy day. So they all spend right up to the limit (the everything cable tv package). Doing this makes them think that they belong in the wealthy class (homes north of $750,000 in my area - Cleveland). They aren't there, of course, but treat all the contractors like they are and demand way more than they paid for (even though they really did spend a lot of money by any global standard). So the landscaping in the hood is all really similar between houses (and nice) but nothing else really beyond typical. Like I said before, my wife and I are really fortunate that we were able to have me build the house. And my mother-in-law in a landscaping / gardening wizard. I have the best landscaping in the hood (for the cost of a couple strong back boys when she shows up to do "extensions").No, the only statues in the hood are in my front yard. Cheapy plastic and cast concrete Buddhas. Perfect.As for the breezeway, it would block more of the inspirational view out back (the hardwood forest).Rob
My shop has a crawl space with treated pine 2x10 joists on 16". The floor is treated pine 3/4" plywood. Just regular, not T&G. The floor is easy to clean, easy on the feet, and has functioned beautifully for 12 years. Easy to put down, too.
No need to overdo it.
Rob,
Sounds like a great setup for the site and situation indeed. So one end will have double doors and could perhaps be used as a garage?.... That could throw a monkey in the works with planners, they would just glance at your plans and see a garage looking floor plan and that is a serious floor.
The plans I would submit would not show double doors/garage door, but build one end with a garage header system, and window and door underneath that could be removed after inspections to retro fit a garage door. I like big doors, easy to load material on the truck and then run out onto table etc. On a nice day it is really nice, and gives some great overflow space for finishing, turning etc.
An under floor DC system or an overhead system? Under floor will be quiet, outside closet for the machine and a return will help reduce dust a bunch as well. Outside closet for the aircompressor is a noise recduction as well.
Great flouescent lighting over the entire shop and some flexible mounting halogen lights on the bench or moving bench areas is great as well. Good light is really nice. Skylights bring natural light, and eleminate the wasted wall space of windows.
FWW had this shop article that I thought had some great considerations. Mat Teague is a pretty sharp guy, and did a lot of homework on this.
Would love to see your final plans and progress photos in the coming months and the myriad of decisions you have to make. There are many here on knots that would enjoy this project vicariously..... drool on keyboards is not always a great thing but I will use my shop towel as needed.
AZMO <!----><!----><!---->
-----------_o
---------_'-,>
-------(*)/ (*) http://www.EarthArtLandscape.com
Azmo,I am not planning the structure for cars because I don't want to get into the extra effort for that. However, I will be framing the front of the structure for a garage door if some poor sap down the line wants to make the change.In place of a garage door I am thinking about making a double 4 x 8 custom built door. Basically, some sort of rail and stile frame (with middle rails and stiles) and plywood in the middle for the panels. This way I'll have an 8 x 8 opening when I need it. I know that sounds a bit fanciful but I have made doors before and it was really quite trivial. Really just bigger than the usual stuff.Dust collection will be under the floor. That means the dust collector and the air compressor (both very noisy) will be located in the crawl space (really enclosed space with a concrete floor). This keeps the noise out and the frees up valuable floor space (20 x 24 is really not that big).I have lots of overhead fluorescent lights now in my garage and couldn't do without so I'll do the same in this building. I am planning on lots of windows looking out back towards the forest and no skylights. I worked for a contractor for 2 years and learned quickly that the only the thing skylights are good for is calls to the contractor to stop the leak. No skylights cause I don't want to have any leaks.Thanks for the article. $40,000 YIKES!!!!! I am no where near that dollar and if I am, the project will get canceled in a heartbeat. I have a very strict budget which means I'll be doing all the work myself and that's ok. I'm very qualified and fairly speedy. I haven't read the whole thing yet so I can't comment on his numbers but I think I might be able to get this done near $10,000. Sounds low??? Not really, that's about right I think. The foundation is the only thing that might throw me off.Thanks for the comments. I'll be giving updates when more happens.Rob
Rob, you don't have any info posted so I am not sure where you live, and construction costs vary so much from Texas to Maine and California. I don't heat or cool or my shop, and that eliminates a large cost. Looks like you need to start a spread sheet to start figuring the costs. My guess... $19000 stem walls, concrete floor in the crawl space, framing, roofing, insulation, electrical, floors, windows, doors etc. It always amazes me how quick it adds up. The 40K shop had a bath in it, that is expensive real estate, with sewer lines, water, hot water, fixtures etc.
I have 9 skylights in my home, office and storage area. None leak a drop and never have. We don't get snow though, and I would not like that issue. Windows up high under the eves from 8' to 10' is nice as well, lots of indirect light.
Don't forget to put in a spot for a chain lift inside the shop as well. Sure nice to pick up and off load this heavy iron stuff with it, can't believe how many times Ihave used mine.... even used it to flip a large slab on my workbench.
Good luck! <!----><!----><!---->
-----------_o
---------_'-,>
-------(*)/ (*) http://www.EarthArtLandscape.com
Rob,
A good, quick way to build doors of the type you describe is to simply cut plywood panels the size of the doors and nail 1x4's flat onto them where you want reinforcement or decoration. This is much simpler than mortising and tenoning and cutting separate interior panels. Plus, the doors never sag.
If you need insulation, you can also sandwich rigid foam between two layers of plywood, with the 1x4 decorative pieces attached to the outmost layer. The interior plywood at that point could be as thin as 1/4 inch...
I made doors like this for my shed, out of 1/2 inch OSB. They've stayed very flat, and once painted look great.
ZoltonIf you see a possum running around in here, kill it. It's not a pet. - Jackie Moon
If I was building a new shop the floor would be well planned and over engineered. I like the idea of T&G 2x6 flooring. You never know what machines you will end up with after 30 or 40 years of woodworking. I started with a Sears contractor saw and now have a Euro slider. A combo slider will weigh about 1500# and a large planner 2000# plus. I would plan for that unless you never plan to upgrade what machines you have.
I have a concrete floor with heavy anti-fatigue mats over most of the floor. The slider sits on a horse stall mat.
Life is what happens to you when you're making other plans.
When your ship comes in... make sure you are not at the airport.
My shop is 24 X 32. The floor is 3/4" ply, nailed and glued over 3X6 joists, 16" O.C., spanning just over 7', over 3X8 girders, spanning 8'. There are no soft spots in the ply or bounce in the framing system.
Also, building to the residential floor framing code leads to bouncy floors. Build to the deflection standard that is acceptable to you, such as that required for tile floors which need stiff framing.
Edited 8/17/2009 11:48 pm ET by 082250
This forum post is now archived. Commenting has been disabled