What Size 2" Beams and Spacing for a 14 ft. Span

Weld county defers and subscribes to the Colorado Chapter of the International Code Council

One service of the Colorado Chapter of the ICC is to offer you these building guides for projects around your home, based on the 2003, 2006, or 2009 ICC code.

I'd suggest the deck guide, and you can probably get away with 2X10 as they will not directly bear snow loads

Thanks for the information. I was not aware that ICC offered this information.

I still have not found a recommended spacing for the floor or ceiling joists.

I presume to be on the safe side, I should probably use 16 inch spacing with the

2 X 10 joists.

Thanks again.

Bob

An older load table that I have (1979 Architectural and Graphic Standards) shows only 12" and 16" spacings for floor joists. For a 40 lb/ft² load and 16" spacing, lumber with modulus of elasticity E = 1,000,000 can span 13'11"; E = 1,200,000 can span 14'9". This is based on deflection. Based on bending strength, the allowable spans depend on tensile strength T. For T = 900, 13'9"; for T = 1000, 14'6".

Your local lumber supplier should be able to give further info, including what type of lumber they can furnish.

Thank you for your recommendations. I guess to be completely safe, I will go

with 2 x 12's joists with 16 inch spacing. I checked with Home Depot and they did

not have the tensile stringth information for their 2 x 10's and 2 x 12's.

They also do not have 14 foot long 2 x 12's so I will have to get 16 footers

unless I can find 14 footers somewhere else.

Does anyone know where I can buy 2 x 12's in 14 ft length in the North Denver area?

Thanks again for your valuable information.

Rancher

It depends on how much load (lb/ft²) you want to support.

These would probably be called joists rather than beams.

I guess I should have about 35 or 40 pounds per Sq foot load carrying capability.

Probably use 2 x 12's joists with 16 inch spacing to be on the safe side. What do you think?

Thanks,

Rancher

Where can I get 2" x 12" by 14 foot joists in the north Denver area?

Home Depot does not have 14 foot length.

Thanks,

Rancher

In my reply (#4) I forgot to say 2x10 as the dimension (just carrying it over from post #3).

Most of the common species of lumber should work with 2x10's on 16" centers. Cedar, spruce, and some types of pine come up short, but the others have sufficient tensile strength and modulus of elasticity. In particular, Western hemlock and Douglas fir are good. Does your lumber supplier know what species is on hand?

I doubt that 14' is a common length, unless by special order.

Thanks,

I'll have to check to see what species of lumber is available. Hopefully it

is not one that "comes up short".

Old rule of thumb, half the span (in feet) plus one =number of inches deep.

14 feet span, one half =7, plus one = 8 inches.

Use 8 x 2 timber.

If you are building a load-bearing roof, like a bedroom floor, space beams 18 ins heavy loads (bookcases, filled cupboards), 2 feet apart moderate loads. Light or unloaded, spread them 3 feet apart

Be aware that the next owner may not understand and respect a low load capacity floor, follow code, this is what it is meant to be.

2 by 8 on 16 inch centers will be too "bouncy" on a fourteen foot span.

I prefer fabricated joists, 12 inch is common.

2 by 10s would be better. 2 by 12 would be very expensive.

If you have access to a lumber mill, then go for the big 'uns. You can always over build safely.

Thanks for your response. Sounds like I need to look for fabricated 12" joists.

If they are not available at our local Lowes of Home Depot, would 2 by 10s be

almost as good? I may have to go to a more specialized lumber yard to get 14 ft

lengths or get 16 ft and cut the excess off.

Thanks,

Rancher

IF you can find lumber that's 14 feet long:

I try a load case of 40 PSF live load, 12 PSF Dead Load, and 2 x 12's @ 18" o.c. supported with Simpson Joist Hangers at each end. you must provide at least 2 parallel rows of joist bridging and nailing of 1/2-inch thick plywood @ 8" o.c.. maximum

W (TL) = 78 PLF (6.50 PLI)

L max = 14 FT. = 168"

Rmax = 546 #

Max. Vd (@ "d" from face of support) = 472.9#

Max. Mb = 22,932 in-#

Max. fv = 42.04 psi

Max. fb = 707.7 psi

max. LL deflection = 0.293" using a conservative E = 1.0xE6 psi

You can use the follow Wood Species and Grades pursuant to the "National Design Specification (NDS) for Wood Construction", "Table 4A Visually Graded Dimension Lumber".

1). Hem-Fir No. 2: Fb = 850 psi, Fv = 150 psi, E = 1,300,000 psi.

2). Spruce-Pine-Fir (SPF) No. 2: Fb= 875 psi, Fv = 135 psi, E = 1,200,000psi.

3). Spruce-Pine-Fir North (SPF North) No. 2: Fb= 775 psi, Fv = 135 psi, E = 1,100,000psi.

4). Southern Pine (SP) No. 2: Fb= 975 psi, Fv = 175 psi, E = 1,600,000psi.

I did not include any Live Load Duration modification Factors (conservative approach), nor any reduction factors for twists, checks, cracks and wetness.

Make sure you purchase lumber that has AFPA grade stamps, is free of twisting, checks and cracks. Also, make sure that the lumber is fairly dry and has a moisture content of less than 19%.......visually grade dimensional lumber with a maximum water moisture content of 15% or less (ie, Kiln Dried) is preferable. IF the lumber is stored under cover and out of the rain you may be able to obtain lumber that is fair dry and has a MC < 19%. Wet lumber will not work for your use at that span and Live Load requirement. Whatever you do, do not overload these floor joists!

Good luck!

===Signed CaptMoosie, BSCE/MSCE/PhD/PE

NYS Licensed & Registered Civil, Structural, & Environmental Engineer

I would go for 10x2 on a 16" centres & use 1" ply flooring,I did this with my workshop to get another floor in and it is solid as a rock, don't forget to double up the joists where the stairs are going.

Bazzer

I would not use 18" OC for your joists, as you will have a fair amount of waste in cutting your plywood flooring. Go with 16" OC. You may find a lumber yard that carries 14' 2x10 or 2x12's, but their hours will be shorter than HD or Lowe's and the price difference may not be that much - all factors you have to weigh. Also, is your span exactly 14' or a little less? If not, you should look at the 16' (I would double check the span all across the area). Keep in mind that you're not looking at a catastrophic failure if going with 2x10 instead of 2x12', you are looking at potentially slightly more deflection in the middle of the span, i.e., 3/4" vs. 1/4".

Also stagger your plywood joints so you never have 4 corners meet together. Use 8p galvanized nails or 2" deck screws to fasten the decking down. On your Simpson (or equivalent) hangers (yes, you ARE going to use hangers), do not use regular nails. You need to use rated nails or screws for the hangers. Do not notch, top or bottom, anywhere in the middle third of any of the joists. confine any holes (like electrical) to the center of the board, and try to keep any holes toward the ends of the joists. The old adage, measure twice, cut once is a good one. It could save you a headache down the road.

Planning ahead will also save headaches later as well: check the space for squareness (or you will be cutting every single sheet at least once), and layout from one side to the other (you may find it better to start from one direction because of interference issues), run your plywood length perpendicular to the joist length as this will give the strongest floor, when laying out the joists be sure to put all the crowns up with the largest crowns in the middle of the floor. And of course the best side of the plywood goes up. You may already know all this but thought I would toss it in anyway. Good luck!

Yes, by all means go with 2x12's @ 16"o/c as Johnathan suggests, instead of my 18" o/c. Also, 1/2" CDX plywood will work for the 16" o/c joist spacings with a 40 psf LL. Yes, 3/4" plywood is better, but it'll be a bear to lift into the barn loft even with 2 workers....

Please note that I was merely showing (by calculation) that it is possible to go up to a spacing of 18" o/c (but no more) with 2x12 lumber using the wood species and grade as indicted in my post.

Personally, having a 14 foot joist span is going to be a bit bouncy when partially loaded with stored items. IF possible, I'd rather see the OP reduce the span by 1/2 by installing a wood stud bearing wall at the mid-span. Having worked on my Great Uncle's & Aunt's dairy farm in the summer during my teenage years I know how perfectly easy it is to overload a floor with stored tools and what not.......and that includes hay lofts up in the main barn.

Today I looked at the construction project and measured the head room from the top of the wood stud bearing wall to the bottom of the horizontal roof trusses. It is only

6ft 4 inch and if I use 10 or 12 inch joists, the head room will be reduced to about

5 ft 4 or 6 inches.

I'm wondering if it would be acceptible to use 2 by 6s or 2 by 8s doubled or trippled

which would allow a little more head room (or less bending over). Do you have any charts or formula's

that would determing if the doubling or tripleing would give me sufficient strength?

I would have to bend over a little regardless of what width joist I use, but the

tripleing of joists with an 8 inch or 6 inch width would certainly reduce the bending over to use the attic like store-room.

Thanks again for your expertise.

Hello wrancher, I'm glad to help you out. I did some engineering work regarding your question and here's the results:

Even if you use one of the crappiest wood species available (Douglas Fir Larch) w/ No. 2 Grade you can get away with installing doubled-up 2x8's spaced at 16" o.c. although the maximum Bending Stresses will be high (fb = 776 psi) they are within acceptable limits (Fb = 1.15 * 850 psi = 997.5 psi). Also, the Live load deflection will be approx. 0.53" or approx. L/320, which is better than the LL deflection limit of L/240 for an unoccupied floor. So, you can get away with using any of the wood species and No. 2 Grade lumber that I had previously mentioned.

Unfortunately, even using doubled-up 2x6 floor joists (@ sp. = 16" o.c.) are not acceptable for your floor joist span and loadings...the Maximum Bending Stress is very high at 1,349 psi (above most Allowable Bending Stresses [Fb] for No. 2 Grade lumber.........also, the Live load Deflection is 1.01" (very high) or ~ L/166.4 > Limit Deflection of L/240.......that option is NOT a good choice for your floor joists. Also, even adding an another 2x6 (to make a 3-2x6 joist) will only make the floor (Dead Load) all that much heavier and will not help you much in the way of strength requirements and LL deflection (calculated to be approx. 0.68" or ~ L/247.1~ very close to the LL Limit of L/240).

Make sure you glue together the 2-2x8 floor joists with a good wood glue, such as Gorilla Glue that is available in Walmart, local hardware stores and the the Big Box stores like Lowes and HD. Also provide 16d nailing along the top and bottom of the joists @ sp. <12" oc....make sure the nails are stagger pattern. and don't forget the 2 parallel rows of joist bridging to prevent the joist from twisting......if you don't install them you negate the entire design & analysis calculation + will not be within the Building Code & the NDS Code/Standards....

Have a great sunny day!

Hello Capt,

Thanks again for your work and all the critical information.

I'm convinced that the 2x8s doubled up will be the best way to go.

Also thanks for the info on glueing and nailing and bridgiing.

Hope I can do something for you sometime.

Have a good one. Rancher

Hello wrancher,

Really no need to thank me, or reciprocate at some later date.....unless you want to ship my way some 100 pounds of frozen prime Angus beef steaks! LOL

Just kidding really!!! Although my stomach is now growling at the possibilities....

I'm glad to have helped you out. When you're done installing your new floor please shoot us a few pics of your handiwork! I'm sure many of us would love to see all the hard work that you've completed.

And I would STILL screw on strap iron along the bottom of those joists....

But that's just me...

Hello Yusef, you're right in that sometimes installing steel strapping is quite necessary, especially if the two pieces of lumber are a little twisted and there's less than adequate contact surface between them.

If there's sufficient contact surface between the two lumber pieces there shouldn't be any problems. This is where the Gorilla Glue comes in, and if the boards are properly clamped together and the glue becomes fully cured, then there's no way those two boards are going to come apart, and that includes prying them apart w/ all manner of tools. If just won't happen at the glue line......no way no how! Instead, the two pieces of wood will separate in any place other than the glue line. I can guarantee it.

I'm very glad a Master Carpenter that was working on our house some 9 years ago suggested that I try Gorilla Glue. I'm glad I did back then, and I've been using it ever since in all manner of wood related projects within our home and that of friends and neighbors....all have been extremely pleased with the results and there hasn't been a adhesive failure yet!!!

Have a great day!

ps: I still want my "Lil Devil" and/or "Lil Ale-e-in" emotion-con included in the bunch here!!!!!

Why use glue and straps? Space the beams with nogging. This will straighten up twisted planks and add a little stiffness to the structure.

The straps I had in mind would simply stiffen the joists....I have used that technique many times. They go the length of the joist along the bottom. A useful technique for a retrofit.

A very rigid and stiff floor would result by running beads of glue on top of the joists and dropping the floor onto it (I use cookies of scrap wood to hold the floor off the joist until the glue is applied, then just knock out the cookies from underneath. Walk on the floor to squeeze the adhesive down nicely, and sink deck screws to solidify the job. This will keep the floor from squeaking. You are still required to nog the joists every six feet or so. We call them dwangs, but the proper term is bridging.

(unnecessary disclaimer...follow the code book for your area....)

But that won't give you the stiff floor you might really need. Just because a floor is built according to code doesn't mean it feels solid! Far from it...minimums are just that...bare minimums. You want to make a dance hall floor, well, for that you have to glue three eights to half inch sheet plywood to the bottom of the joists. Hold them in place with deck screws and let dry. You now have a big wide box beam which will simply not bounce at all. Any time I have had a bouncy floor, I have done this in whole or in part, and the results were amazing.

The reason I have done this is because the code is so "minimum" that many of my clients have been left with bouncy floors by rush job contractors. That is how I fixed the perceived problem.

Note that I have not suggested deviating from code, but rather, adding to it.

Thanks again for the clarification. Sounds like a great idea.

If you go for 8" joists close the spacings to 12"

Bazzer

I was wondering how much head room you had. You can greatly improve the load bearing capacity of smaller profile timber beams by using flitch plates. http://en.wikipedia.org/wiki/Flitch_beam I have used this technique many times in the past where sub floor clearance was an issue. Don't forget to nog the joists, to stop them from twisting under load. Mezzanine floors are great way to make the ground pay if you have the head room. Your shed will be the envy of others.

Thanks for your valuable response. My head room is not going to be sufficient for

walking except posssibly the space between rafters or trusses. The distance from the top of the wood stud bearing wall to the bottom of the horizontal portion of the rafter is 6 ft. 4 inch so I would only be using that area for storage. I would need to reduce the head room by the width of the 2 inch joists which would leave me with insufficient space to walk without bending over. I'm 6 ft. 1 inch tall.

I'll check on the flitch plates for additional load bearing capacity. That will certainly help.

Thanks for all of your help and info. Rancher

codes aside, i think bar joist would be a bette choice.

What is "bar joist"? Is that a double joist with a metal reinforcement "bar" sandwiched between the two joists?

Can I use double 8 inch joists with 16 inch spacing with the bar sandwiched in

or could I get by without the bar?

Thanks, Rancher

no, that's not what a bar joist is. it would take me forever to describe one, but they're all steel. look on web.

I've already started with the double 2 by 8s, but thanks. I'll look into it before I build again. Rancher

What Anon. Poster #1 is describing is what is commonly referred to as an "Open-web Steel Joist". They're far too expensive for your DIY barn construction, plus they need to be fabricated at your local steel fabricator. They're more often than not found in commercial building, factories, retail stores and warehouses. If you've ever have been in a Walmart store and looked up at the open ceiling then you're seen an open-web steel joist.

You can see what they look like at the Steel Joist Institute (SJI) website:

www.steeljoist.org

Rancher, possibly what you're thinking about is what is called a "flitch beam", typically 2 pieces of dimensional lumber sandwiching a vertically oriented steel plate........the lumber is secured to the steel plate with usually 2 rows of structural grade bolts (like ASTM A325-F), washers and nuts, top & bottom. The bolt holes as drilled or punched beforehand, usually in a steel fabricator's shop. They're very strong, and you'll need a Structural Engineer (PE) to design it properly for you as there are certain critical factors that must be checked in the steel, the wood, and the bolts. In your case, adding all that extra steel weight & bolts is really unnecessary, unless you seriously want to increase the Live Load carrying capacity beyond 40 PSF.

IMO, you're fine with the doubled-up 2x8's (at 16" o/c/) that are glued & nailed together pursuant to my previous posting.

Good luck!

Thanks again. That is precisely what we are doing: The two 2 by 8s

glued and nailed together. Rancher

Add a diagonal truss member at each end of the span, extending 24" out from the wall at the top, extending down to the intersection of the wall and floor. Use 3/4" gusset plates on both sides of the joist/diagonal with gorilla glue and nails. This will effectively reduce the span to 10 feet enabling you to use 8" joists. This will work if you can spare the loss of a little space iwo the diagonals.

No need to add diagonal gusset plates at each end when there's 2-2x8's (Hem-Fir No. Grade or better w/ MC<19%) spaced at 16" o.c. and LL = 40 psf. The design repetitive bending stresses, perpendicular shear stresses @ "d" distance from face of support, horiz. shear stresses @ supports (based on contact area), and the LL deflection are all within tolerable limits (ie, they're all less than the modified Allowable Stresses for that wood species and visual grading), and conform to the Building Code. I've already done the necessary calculations pursuant to the National Design Specification (NDS) for Wood. Everything is fine, UNLESS the OP desires to support a heavier Live load.

By adding the gussets at each end you are essentially shifting the "d" distance from face of support inwards towards the center of the joist, and thus allowing the joists to be loaded higher and for a greater vertical end reactions....but, for this to be valid relative to the NDS then both ends of the joists must be resting atop a seat, and not just have plywood gussets slapped onto their sides [Note: There must be a solid seat (or stiffened beam seat) or a structurally-effective resting contact area under the ends of the joists...Simpson Strong-Tie floor joist hangers 3" wide would qualify, but they don't reach out 24-inches from the supporting walls, only about 2 inches.].

Thanks again. Rancher

I have a neigbour who is putting up open web wooden joists in his barn. He has to hold a LOT of hay, so his are pretty big. He got them from here. The design seems to me to be very VERY interesting. Mostly because it can be scaled up so easily! (Perhaps a bit overkill for wrancher's feed shed, but hey, there will be other buildings coming down the road! These are becoming really common around here. You used to see it as pre built trusses, this is a trussed joint.

I have had building inspectors tell me that they are not happy with any of the lumber coming out of the mills these days. Apparently, the standards were all made with old growth stuff in mind, and after many many years of re-forestation, the new growth stuff is flimsier and softer. Upside...its easier to nail into and warps less upon drying. Downside, it now takes a ten inch beam to do the job of an old eight inch beam! Or to put it another way, floors made with modern lumber are bouncier. (It was not just you imagination!) And with 2 by 12's being nearly three times the price of 2 by 10's, you can see why folks are going with manufactured beams.

That being said, there is a considerable movement in the construction industry around here to utilize steel web beams. Not the old standby that you can see by looking up to the ceiling at any Wal Mart, but rather a composite steel and lumber joist which is normally built up on site. These are two by four lengths which are separated by steel bars...lower shipping costs are a big plus, especially up in the Canadian North where shipping costs are significant. Here is a link to the engineering study. Its from the Canadian National Research Council. You might find it useful. Either way, I would be delighted to see some feedback, and this thread is as good a thread as any!

Thanks for doing all that great engineering! You rarely see it in the intensely practical world I inhabit, but its only barely more important than one's own heartbeat.

Thanks,

I already have my joists in place, but , like you said, this could certainly be considered next time.

Rancher

Yusef, thanks for the information and links.

We've had those hybrid open web floor trusses down here for some time now, and I like using them in my designs.

There are other alternatives too:

1. Fabricated wood trusses with steel gusset plates (see www.tpinst.org ; the Truss Plate Institute), which are fabricated around these parts most frequently. Major lumber suppliers actually design and fabricate them.

2. TJI's....Truss Joist Institute....an engineered wood I-beam which are very strong and economical.

3. Microlam beams....ditto....I love these beams, and have specified them the most on upscale home projects and commercial projects.....incredibly strong!

4. Open-web hybrid floor joists featuring steel web bar sandwiched between 2 wood top & bottom chord pieces.

I agree with you about the crappy dimensional lumber that's available in the last 15 to 20 years that's being passed off for "good" lumber. In my opinion it's a huge step backwards and gives the entire construction industry a black eye.