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I’m fixing to build a workshop, 800sf over two floors. Measures 31’x26′. A W12x35 steel beam, 26′, will span (clear span) across the building, with appx 15′ floor joists (No.2 SYP 2×10’s 12″o.c.) connecting between the end walls (2×4 walls, 8′ stud over 2′ block wall) and the beam (nailer bolted to web, joists in metal strap hangers). Flooring is to be 3/4″ T&G plywood, screwed and glued.
Upstairs will be storage (20’x7′) room with full-height 2’d shelving, and full workworking shop (tablesaw, bandsaw, drill press, etc). I have figured this at 50psf liveload, 20psf dead load, 360 deflection.
Is this loading realistic? Too much? I want solid, stiff floors, what with the machinery and all. Am I overbuilding it? I almost want to go to 2×12 on 12″, using 60psf/20psf/360. Any better ideas/recommendations?
alad
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Alad,
Have you looked at TJI's for your floor system?
Dave
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First of all, I am not an enginer of architech just a sometimes builder. All my reference books are at home, but I would guess that while your design sounds to me like it will support the load, (though the storage area may be questionable, what are you putting on that full height shelving?) I don't think it's going feel very "solid, stiff". a 1/360 deflection sounds pretty stiff, but I suspect it may "feel" a bit bouncy, but I could be wrong. If I were doing it I think I'd want to use 2 beams and shorter joists.
Jay
*alad- your loading is not unrealistic but perhaps needs further scrutiny in regards to the actual distribution of loading. I will give you ANSI Minimum Distributed Live Loads for various occupancies- you need to determine which governs, or use good judgement as to what actual LL you will design for.Libraries, Stack Rooms: 150 psfManufacturing, Heavy: 150 psf " , Light 100Residential Dwelling, 1st floor: 40 psfGarages, Gen'l Storage and repair: 100 psfGarages, Private pleasure, car storage: 50 psfAs you can see, there is a wide variation. Realize , fro example, that manufacturing ll's assume forklift traffic, not likely in your situation. Yours falls under what I would call mixed loading and I would suggest you look at your actual distribution of loading and worst case transient live loading (i.e. what are the largest likely projects you will be working on, and what type of loads will it impose?). I'd take a serious look at the stack loads and what LL it will impose-it is equivalent to library loading if they are loaded fully (book loads are very heavy). Your dead loads are just that, the actual weight of the materials given the size and spacing specified. The ANSI/ASCE code is the best guidance in determining these loads. Sorry my answer probably raises more questions than it answers, but as a PE, and not knowing all the particulars of your structure, I can only give you general guidance. It sounds as if you are taking a good common sense look at your situation.
*I did look at 2x4 floor trusses, the problem there is truss depth - 18" deep for the span, 16" o.c. I'm trying to keep overall bldg height managable - this is in a residential area, R-20.Don't see many (any) TJI's used around here -- I'll check around for span tables tomorrow.alad
*The 20x7 storage room will lay alongside the long dimension of the upstairs area, along one outside wall. Shelves will be 2' deep, and will hold anything from misc tools, to old Jeep parts, failed projects, old PC's -- just the ordinary collection of "stuff" that accumulates in a shop or garage. Hard to put a number on it.I thought about adding a second beam, splitting the floor joist system into thirds, with appx 10' joists. The numbers I ran earlier did put me at the upper end of the allowable spans. The W12x35 26' will run me about $265, so that's really not a problem.I was also just thinking about figuring for a point load, so I could put a trolley and chainfall on the lower flange. I have a client that's a PE/Architect, maybe I'll buy him lunch this week.DP
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Alad:
Based on the infor you provided, and assuming that all roof loads are transferred to the exterior walls, your floor joists are OK. You are actually getting a deflection of about L/265-L/335 depending on what you use for E. I dont think L/360 is being too conservative..who wants a bouncy floor? Assuming you have no columns under your 26' beam span, the W12x35 is overstressed and the deflection is approx. L/240. You need to go to a larger section if you want to free span the 26 foot,something on the order of a W14x43. Id add a column and footing under the beam, and have an engineer check it for you.
Good Luck....Dave
*Fred, I question the loads, too. I think that 100 - 125psf for storage is reasonable. As soon as you call an occupancy storage, the required load increases a lot. It is all too easy to say you won't exceed a load and then you do. 3 boxes of drywall mud is 150# . It's not hard to imagine full height storage being much more. Average it out over the aisles and you get 100 psf, easily. Err on the side of caution.
*Alad:I went back and re-read your post and now am not sure I understand the layout of the building. Mike and Fred are both correct in questioning the load. I think the UBC minimum floor design load for storage areas is 100psf. And remember the UBC is the minimum requirements. Give the description another shot.Dave
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Alad;
You mention the cost of another beam not being a problem, but there is more than just the beam, something has to hold the beam up, but with twice as many columns/footings each one can be smaller. And with the reduced joist span, you could increse the joist spacing and save lumber (and minimise the added number of hangers), also the price per bft _might_ be a little less for shorter lengths.
I checked the ASIC-ASD handbook last night, and now I'm pretty sure that the deflection would be more than you'd like with a single W12x35. Today I see that Dave thinks that a W12x35 would be overstressed, it certainly would be at 100psf over the entire area, but your storage area is only a small part of the total, but that also means the loading is not uniform, so this probably is something a professional should check.
(though if I were doing this I would definatly use two beams and would probably consider that conservative enough)
You said "nailer bolted to web, joists in metal strap hangers", I'm not sure I've ever seen that done, but it sounds like it might be good idea since the joists would then provide lateral support for the beam, though unless you use 3x stock for the nailer you'll have to notch the joists for the top flange. You need to remember the wood will shrink as it dries out, but the steel won't, so you need to be sure your bolts don't tear apart the wood, and if you set your joists flush with the top of the beam you'll have speed bumps in your floor in a month or so :)
Jay
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I think the 100# live load suggested is way out of line. No way you could get that in a shop. You might get more than 100# in a single square foot, but not if you averaged it out over several square feet. A 10' by 10' area with 50# loading is capable of carrying 5,000#. I can't see getting more load than that on a shop/storage floor.
2X10s are probably adequate, but why put them 12" OC ? I would suggest using 2X12s at 16" OC instead. Remember that stiffness comes from depth, not from reduced OC spacing. You would get a stiffer floor for about the same price.
I-joists aren't a bad choice here either. I don't personally like them a lot due to fire performance limitations, but other than that they're fine.
Another option would be 12" deep floor trusses (keeping the beam) Don't go for the clear span 18" deep trusses - they're too shallow for that long a span, and will not be stiff.
Best of luck with your shop. Think I could come over some weekend and borrow it ? (-:
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Thanks for all the help, friends. I'll try to work up some way the next couple of days to post my floor plans here, even if it's just a tiny .jpg, you'll have a better idea of what the layout will be.
BTW, I'm actually downsizing, the workshop I'm borrowing now (and losing) is 3000 sf divided over two floors. In town, city building code limits outbuildings to an 800sf footprint. But I can go 40' tall -- that could be three eight foot walls over a ten foot wall, plus the gable height. Pretty stupid code, huh?
alad
*100 psf is not unreasonable. The poster says he will have stack loads and ANSI loads for this type of occupancy put LL between 50-150 psf. Based on code requirements and the fact that the posters occupancy does not fall into a rigid classification, the designer must make an educated judgement as to what LL to design for.I would also caution against giving anything but general guidance to someone in this forum- you don't know what the exact loading the occupant will eventually have or what information is or is not volunteered.
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Fred, again I second your opinion. To suggest that the code load for storage is out of line is irresponsible. 3 stacked boxes of drywall mud, left over from a job, is 150 psf and only about 2' high. The original post suggests 8' high shelves. It would be easy to load that up to 100psf or greater.
*Ron,Just WHAT IS IT about wood I-joists that contributes to their fire performance limitations? I have never heard this before (it's true, I'm not up on code) so I'm curious about this.Thanx,Brian
*Brian -My concern about I-joists and fire performance is personal, and not based on any research or code info. It just seems that the 3/8" thick plywood web wouldn't take too long to burn through in a fire. If much of the web burned through, the floor could collapse. I'm sure the I-joist manufacturers have done testing on this, but I've never seen any documentation on it. Anybody else know anything about this ?
*Fred, I am assuming that you are referring to my post when you caution against giving any more than general advice. Its terrible how the legal "profession" has such a grip on all aspects of our lives. Alad, alas, Fred is right, we dont know all the details and are making assumptions about what the configuration actually is, so, the best advice is finalize your drawings then have a PE check it for you and make recommendations for changes. P.S. It is my *opinion* that you will see loads potentially is excess of 100psf, as has been statedDave
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I'm fixing to build a workshop, 800sf over two floors. Measures 31'x26'. A W12x35 steel beam, 26', will span (clear span) across the building, with appx 15' floor joists (No.2 SYP 2x10's 12"o.c.) connecting between the end walls (2x4 walls, 8' stud over 2' block wall) and the beam (nailer bolted to web, joists in metal strap hangers). Flooring is to be 3/4" T&G plywood, screwed and glued.
Upstairs will be storage (20'x7') room with full-height 2'd shelving, and full workworking shop (tablesaw, bandsaw, drill press, etc). I have figured this at 50psf liveload, 20psf dead load, 360 deflection.
Is this loading realistic? Too much? I want solid, stiff floors, what with the machinery and all. Am I overbuilding it? I almost want to go to 2x12 on 12", using 60psf/20psf/360. Any better ideas/recommendations?
alad