Barn Floor - Joist Layout

Hi all,

It's been a while since posting on the TFG forum, but I've recently begun work on the second barn on my Vermont farm. A month ago I completed the rubble trench and will pour the footings (grade beams) in the spring atop which the stem walls will sit.

Over the course of the winter I'd like to firm up the design for the first floor decking. (The barn will have a wooden floor over a crawlspace and root cellar below.)

I've attached a picture of my current sill/girder/joist layout. I'd sure love any feedback/tips/design considerations you can offer. The central bays are 12' x 12'. The two bays inside the barn entrance will need to support a tractor and/or implements. (The bays on the overhang will be a shop with lesser loads.) I'm okay with calculating beam sizing based on loads. What I'm most curious about are layout options (use of summer beams, joists perpendicular or parallel with longitudinal sills, etc.)

I've tried to do a bit of research online, but it seems that very few barns are built these days with a timber floor.

Thanks in advance,
[img]http://www.paddleways.com/blog/gypsyrose/images/MonitorBarnFloorJoists.jpg[/img]

Kevin,

I came up with a joist/sleeper system that I have seen in some barns is Wisconsin. There is less notching, (which will save on labor, and since all the joists will be hidden under the flooring in the crawl space, you wouldn't know that they weren't "joined".)

I dropped the main sleepers to go under the lower sill tie-beams, and the joists then sit on the sleepers and are at the same elevation. I also added extra joist down the driveway mow/bay and an extra sleeper down the middle to help carrier the live load of moving equipment around. You should be able to create pockets in the concrete walls to let the sleepers transfer load.

Good Luck,

Rooster

[IMG]http://i453.photobucket.com/albums/qq254/crwtimberframe/Z%20misc/BarnJoistlayout2D2.jpg[/IMG]

[IMG]http://i453.photobucket.com/albums/qq254/crwtimberframe/Z%20misc/BarnJoistlayout2D1.jpg[/IMG]

Lodging them as Rooster suggest, works the best in my book. I second it.

Hi Kevin;

Traditionally the drive floor joists ran longitudinally and the aisle joists ran like you have them. However, the barn door is the most likely place for the sill to rot so with your plan future repairs of the sill at the barn door will be easier (unless the rot extends under the posts beside the doors!). Use a rot resistant wood within 18" of the ground. (Can you tell I do a lot of sill work!)

I like Craig's layout too. The framing does not tie all of the sills together but the floor planks will do that.

Venting a crawl space is still a controversial subject, but I would do it. Don't forget to make an door or hatch to access the crawl space.

Is your root cellar o.k. on an outside wall?

I do not think you need braces back toward the main foundation in the "forebay".

Any chance you will want to waste some space with a stairway to ground level in the "forebay"?

Best wishes;
Jim

Jim,

I'd read a piece in one of the TFG workbooks about the potential for springy floors if all joists are running the same direction (setting up a form of harmonic). I'm hoping that it won't be an issue with the relatively small spans in this barn.

Craig's sleeper layout has gotten me thinking about forms other than joined members.

I'm planning on having the foundation rise 16" above the exterior grade, topped with a layer of PT (under the sill beams). (There will be more height inside the crawlspace.) Sill rot at the entrance is something I'll be giving a good deal of thought to. Any thoughts on options?

Yes, the root cellar will have one wall that won't be earth-insulated. I'm hoping that insulating the interior of that wall (plus the ceiling) will keep things above freezing. I've got to sort out how best to vent the root cellar. Some vegetables want humidity, others don't. I worry about moisture buildup if humidity gets too high. As for venting the rest of the crawlspace, I don't have any planned (except the air that moves up through the wooden floor). Admittedly, moisture control is a topic I'm still trying to get my head around. I've read much of the debate but haven't come to any solid conclusions.

I plan to put in a hatch from the floor down into the crawlspace. There will also be an outside entrance (stairway) to the forebay (shop) area.

Thanks for the feedback.

After looking at the loading on the timbers in the above grade section of the barn (the "forebays" as Jim called it) I realized that I'd need some pretty substantial timber in the ties to support the load over 14' if the joists in all bays were oriented in the same direction. By turning the middle bay joists 90 degrees (see attached image) I've been able to bring the deflection to acceptable levels for a 57.5 psf load without having to resort to timbers greater than 8" in height.
Is there anything I may be overlooking?

[img:left]http://www.paddleways.com/blog/gypsyrose/images/MonitorBarnFloorJoistsV2.jpg[/img]

From what I can find on online, I'm seeing a wild range of numbers for barn floor design loads - anywhere from 40 psf to 150+ psf for live loads. (I suppose it's a result of the wide variability of barn uses.) My search hasn't turned up IBC numbers, however. Do any of you have a link or any insights on what acceptable numbers are for first floor design loads in a barn?

Thanks!

Tough to say Kevin. Remember too that your decking will need to be able to take the point load from the tractor wheels.

How much does the tractor and implements way? I imagine somewhere between 4 and 8k?


I just finished some drawings with 150 psf load for the hay loft.
Thankfully the first floor is @ grade. Cows are heavy!

My guess is that you'll be looking at 150 to 200 psf to start. Likely 3x decking if you are bringing in vehicles.

In a case like this, I would strongly recommend over engineering the floor. I know how expensive farm equipment can be...
It might also be advisable not only to use thick decking, but also run two layers, the top layer run at a right angle to the bottom layer. This will help to distribute loads across the decking boards, which will in turn help to distribute the weight on the joists more efficiently. It will also lessen the impact of a failure in any single piece of decking.

and also, use cottonwood for the drive floor if you will be driving equipment over it, it will not break and shatter like some other woods. Just be sure and don't let it covered with hay or stray, or it might get damp and rot out

I don't expect any more than 10,000 lbs of weight per bay. Loading it up with hay would be heavier. At the moment, the design is for 100 psf.

Here's my latest thinking:

Floor Joist Layout

On Craig's suggestion (and knowing that it was the way in many old barns), I looked at configurations of sleepers. The part I didn't like, however, was embedding the ends of the sleepers in the concrete. I also wanted to keep the beam size a bit smaller than the sleepers would require. I've ended up (for the moment) with the configuration in the link above. By adding a post to the middle of the central span I can get the loads supported without having to resort to a giant member in the middle of the drive bay. It's been an evolving puzzle. Thanks for your input.

> It might also be advisable not only to use thick decking, but also run two layers . . .

I plan to run two layers of decking - 5/4 each. I've got a lot of white ash that I've been thinking of sawing up for the top layer of the decking. (The primary species I have to work with are hemlock, maple, ash and cherry. The maple is reserved for sugar and some of the cherry is gonna go into new kitchen cabinets one day.)

White ash works good, a lot of old barns around here have ash in the lofts (which in other areas folks call hay mow)
But if you can find cottonwood, I would highly recommend using it for the top layer.
The advantage of cottonwood is that it is 'spongy' -the fibers in the wood will compress and crush under extreme loads, but will spring back to their normal state. This makes the wood incredibly tough and durable. Old timers made their floors out of cottonwood because it could take a serious beating.
Ash under a crushing load will be crushed, and the fibers destroyed.

I am a big fan also of like you said supporting your floor with a mid-span post.
I am not sure exactly what you are describing, but what I would do is have posts to support a beam upon which the joists merely set, they do not have to be joined at all, here gravity can do ALL the work.
I know this idea works very well, and I can show you examples of castle floors framed in the 12th and 13th centuries like this that are still functioning well to this day under heavy loads.

Hey,

It looks like we have a lot of positive input with regards to your floor layout. I would like to clarify a few things about the floor framing that I proposed.

The ends of the main sleepers are merely setting into pockets created in the inside face of the concrete wall, they are not embedded per say. The original layout that this was based off of was from a bank barn that had 24 in.thick mortared feildstone walls for the foundation...which allows for a lot of surface area on top of the wall for the sill beams and the lower tie-beams. I recently looked at a hand hewn barn frame that had two 14 x 16 x 22ft beams in the floor system that carried the load of the joists, and they were both resting in pockets in the stone wall. Another option would be to add a concrete or block column to the inside surface of the wall that would carry the sleepers.

The additional sleeper that supports the midspan of the joists, is there to reduce the span load by 1/2...adding one beam, allows all the joists to be supported where they need it most instead of them just being supported at their ends.

I hope this helps.

Rooster

Craig,

I'll be laying up the stem walls for the barn in concrete block. I'd thought that the easiest way to support the sleepers would be to build out the wall on the inside of the foundation under the sleepers, as you suggested. I'd want to isolate the timbers from contact with the concrete with a layer of PT between. Seeing old foundations with timber ends drawing moisture from direct contact with the masonry raised my concerns about putting the sleepers directly onto concrete. Did the one that you'd looked at have any moisture problems at the timber ends?

Kevin,

I would agree that adding a PT block between the sleeper and the concrete block would help with any moisture transfer. The hand hewn beams that I was referencing were White Oak, and I did not see any significant signs of moisture problems. The sill beams of this barn sat directly on a mortared cap of the fieldstone walls. I often find some rot or water damage on many of the barns that I restore. These were built before the advent of pressure treated lumber. You would obviously want your barns to last as long if not longer than those that I have worked on, so I would encourage you to take the appropriate steps to ensure the future of your barn, well after both you and I are gone. My Moto is "Building on the Past for the Future to Hold."

Rooster

Craig,

I love that motto!

Thanks for all your feedback. It has really helped me refine plans for a barn that I hope will serve many generations.

I, too, have found very little in the way of contemporary barns with timbers on the first floor deck.

Best,
~ Kevin

What would you like to discuss Michael John?

I bet it wants to sell you some paper gold certificates. Or something worse.

I got lost on this one??? please explain.

Spam I suspect, Jay.

Yes, it is spam. What the spammer is promoting is point enhancement and level raising for online gamers in violation of user agreements. This is a hacker-spammer enterprise and posts should be removed.

thank you Roger, et al.

I agree it should be removed and better screened if at all possible.

Has anyone tried out that little 'notify' button? I haven't seen anything come to my inbox... so if you have used notify - we might need to turn some dials and flip some switches in the background.

Seems I'm the only moderator that spends any time here... I can't see everything coming in - but I do try to clean this stuff up. This one has been removed.

Test notification sent.

Hi Mike, thanks for all your hard work, and yes I did, but it must not have take hold????

Thanks Gents. I have not received. I'll flip some switches and see what I can do so I get notices...

-mb

Mike, while you are looking under the hood, could you change the default setting on viewing the forum from threaded mode to flat mode? That one change would make the forum much easier to view for guests and other new comers, since they could just scroll through the conversation as it takes place in time.

That should be in your personal settings. My view starts with the oldest post and works down to the newest post, ten to a page.

Dave, I am aware of the of the preferences menu and I have set my view to flat mode as you evidently done. For unregistered viewers there is no option for changing the view, they must view the page by the default of threaded mode, which can be completely cumbersome and unreadable. Try logging out and call up Northern Hewers Historic Hewing Questionaire thread. I think you would find the threaded mode the most frustrating reading experience you've had in a very long time.

So in the interest of forum improvement, flat mode should be the default mode. Let's hope small improvements can make the forum grow a little.

I made the view switch. I cannot find where to toggle me receiving spam alerts. Will get in there again later and try to poke around some more.

Roger, I understand now.

Mike, thanks for taking the time to run this place.