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