16 x 24 Pole barn planned for the spring

[quicksandfarmer]

The loft looks a lot like the construction of a deck. What you're calling eave rafters would be called beams in a deck. The post would normally be notched and they would be bolted to the post. The joists should have blocking or bracing to keep them from twisting, and should be fastened to the beam with hurricane clips or some other way of keeping them from lifting or shifting. This is particularly important if the roof is attached to the joists as wind uplift could take the whole second floor off.

For the size of the beam: earlier we were throwing around a 10 psf dead load and 40 psf live load or 50 psf total. Each section is 16x8=128 square feet, or 6400 lbs. That is held by one beam on each side so each beam has to hold 3200 lbs for the floor plus whatever the roof contributes (maybe 40 psf? Ask your inspector about local snow loads). That's going to be at least two 2x12 or possibly three. This is why you need notching and bolts, there's thousands of pounds on that joint.


If you look at a beam chart for decks you'll find that 16' joist span and 8' post spacing puts you in the far corner of the chart, near the section that says "engineered beam required."

You'll need something to prevent uplift where the rafters attach to the joists or beams.

Each of the center posts is going to be holding 64 square feet of floor (3200 lbs) and 64 square feet of roof (2560 lbs?) or 5760 lbs. You need to make sure your footings are big enough to hold that load, otherwise your posts will sink. A 6x6 has a bearing area of 30.5 square inches, about 0.2 square feet. Check with your building official but a common number for soil bearing capacity is 1500 lbs per square foot. So each post needs about four square feet of footing, that's a 2x2 concrete pad under the post.

There's a lot of info about designing decks on the Internet, I would view this as designing a 16x24 deck with walls and a roof added on.

 

[EddieWalker]

Since the changed the formula on pressure treated wood, I've seen 4x6's twist. I never noticed it before, but you can't even find a dozen of them in a pallet at the store that are straight. Get them home and half of them are turning on you in a week. I wont use them for a client anymore. the only thing I will use are 6x6's. They are heavier, they cost more and they are way overkill. But they stay straight, and for me, that's worth the extra cost and hassle dealing with the weight.

I don't thin anybody mention it, but some builders are using treated 2x6's and laminating them together. Structurally, they are plenty strong enough, but if you put them in the ground, they need to be rated for ground contact. Most 2x6's are not rated for this and it is something you will have to special order. There is an advantage to not having to notch the posts if you go this way, but it's not hard to notch a post and I like the process of notching them, so I like to stick with what works and I can guarantee my clients is going to last.

For the roof structure and the spans you are working with, 2x6's are perfect. I would look at gambrel roof truss designs and see if you want to stick with that design, or add to it. The only concern is snow and wind loads. If that isn't a concern, then the design you posted should be fine.

For me, I've regretted every shortcut I've ever taken, and every time I've tried to save a buck. Spend what it takes to do it right the first time, and you will never have any regrets.

Eddie

 

[lovemytoys]

i used pre made trusses

 

[lovemytoys]

pics i built this last year

 

[lovemytoys]

it cost me about 90 for each truss

 

[YardBikeBob]

Do not build your roof out of 2x4's!!!! This is going to give you too much movement over time and lead to issues. I like half inch plywood for your gussets. I use liquid nails and deck screws to hold it all together. I don't like nails and try to use screws as much as possible.
Eddie

There ya go! Using 2 by 4 stock for roof beams will never hold up. When we bought this place I was sure disappointed with the construction methods on the barn we inherited. The roof is all 2x4s and simple iron nails!


I sure would like to have a long talk with the builder! The way things are going it won't make it another 70 years.

Bob

 

[Hiltz]

In maple syrup production, the rule of thumb is to build your sugar house twice as big as you think you'll need... That way you'll only have to add-on once.[/QUOTE

Im gonna steal that last part from you.

 

[YardBikeBob]

I like the liquid nails and screws idea-would 2 x 6s be adequate?

I would use 'construction adhesive' in the 28oz tubes. Then 2" x .113 galvanized in an air nailer for those 1/2" plywood truss joints. Cheaper, faster. Do the rafter deck and nail it down for a flat spot then screw scrap pieces to the floor as a jig for your gambrel trusses.

Framing nailers are no longer that expensive: 3-in-1 Air Framing Nailer - 10 Gauge

As you're not using roof sheathing, the nailer running 3 1/2s could attach the purlins, too. Sure, a good screwin' might be better but if you're just one guy and only got weekends. . .

Bob

 

[Hiltz]

If your projects size is somewhat confined by your lot size you could cantilever your floor joists 12" out over your walls. Your trusses would then be set 12" farther outside the lower walls. I would think the cost would be minimal and this would give you extra space without compromising the footprint of the building. It would also have the benefit of sheding water off and away from the side walls. Cheers

 

[GPintheMitten]

Consider going taller. A 10 foot eave is more practical for your future lean to.