I have been reading over forum posts regarding pole barn construction for many months now. However, I have a few questions that I was unable to find answers to. I just this morning took the first delivery of material for my new 24x28x8 pole barn. A couple concerns I have regarding the plans is the 2x12 (header?) that the trusses sit on is simply nailed to the posts. With a moderate amount of snow in central PA and the odd blizzard that dumps 2-3 feet I am concerned that this might be a weak spot in the design. I am thinking that it might be more appropriate to throughbolt the board to the posts with carriage bolts in addition to nails. I should note that there is a board on the inside and outside of the posts. Also the plans call for only 2'8" of post depth and an additional 10" of concrete. I understand that with the concrete frost depth is not a problem, however, lateral stability may be compromised with this shorter depth. Thoughts?
pole barn question
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herd
Gold Member
You would need to explain more about how you're constructing this shed in order to answer about the header load. If you're doinng a "pole shed'' design with 6x6 posts on 10 or 12 foot centers with prebilt trusses and using 2x6 perlins on 32'' centers, the perimeter band will just that, it will not carry the load as the post and trusses will do that.
Now if you're building a conventional roof systems with either 16'' or 24'' rafters/joists on center, then you need a sturdy, solid header. In that design, I would use either 2x10 or 2x12 with .5'' plywood, glued and staggered, nailed both sides with 16d cc's.
If you're sitting the trusses on top the post, I prefer to notch mine down one side the lenght of the truss thickness, then nail and bolt. When done, you will need diagonal wind braces. That along with your perlins will make the structure quite sturdy.
As far as post depth, I prefer 36'', but 32'' with concrecte on an 8' height is plenty. I guess it depends on whether you're digging by hand or with equipment as the soil gets hard at that depth.
Good luck, I am putting up a 24'w by 35'd in a week or so. I will be doing 3 trusses on 12' centers using 2x6 perlins on 32'' centers, using Imperial Ridge painted steel for roofing.
BTW, you didn't mention treated lumber, use treated for your posted, untreated for anything that touches the metal. Treated will rush your metal. You may also want to use a vapor barrier under your metal.
Now if you're building a conventional roof systems with either 16'' or 24'' rafters/joists on center, then you need a sturdy, solid header. In that design, I would use either 2x10 or 2x12 with .5'' plywood, glued and staggered, nailed both sides with 16d cc's.
If you're sitting the trusses on top the post, I prefer to notch mine down one side the lenght of the truss thickness, then nail and bolt. When done, you will need diagonal wind braces. That along with your perlins will make the structure quite sturdy.
As far as post depth, I prefer 36'', but 32'' with concrecte on an 8' height is plenty. I guess it depends on whether you're digging by hand or with equipment as the soil gets hard at that depth.
Good luck, I am putting up a 24'w by 35'd in a week or so. I will be doing 3 trusses on 12' centers using 2x6 perlins on 32'' centers, using Imperial Ridge painted steel for roofing.
BTW, you didn't mention treated lumber, use treated for your posted, untreated for anything that touches the metal. Treated will rush your metal. You may also want to use a vapor barrier under your metal.
MarkV
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Thoughts. Well if you are working from engineered plans someone has done the math to show that the nails will have enough sheer strength for the header to post connection. That said, I always through bolt or lag to the posts. Makes me feel better.
MarkV
The only concern with the information provided will be your bracing/purlins. IF the truss requires permanent lateral bracing of the web members, it may be difficult to find the length materials you would require. Check with you truss manufacturer, ideally the bracing members are not butted end to end but rather it is recommended that it runs past to the previous truss, thus could make your bracing and purlins difficult to impossible to purchase.
The bracing, there is a work around, instead of running the material laterally, you can possibly (depending on your design) do an "I" or "L" type "scab".
In the event of high winds, the structure could "rack" and with the bracing butted end to end, hummmm a lot of stresses their anyhow, not sure I would add to the list of potential problems.
JW <'/))))><
The bracing, there is a work around, instead of running the material laterally, you can possibly (depending on your design) do an "I" or "L" type "scab".
In the event of high winds, the structure could "rack" and with the bracing butted end to end, hummmm a lot of stresses their anyhow, not sure I would add to the list of potential problems.
JW <'/))))><
patrick_g
Elite Member
I prefer through bolts over nails or even screws or lags. More work and expense but I don't have any doubts regarding longevity. I have seen lots of really strong structures that weakened over time when wood cracked, wind loads repetitively worked on joints till they loosened, and such.
But then, I typically over engineer my projects in self defense.
Pat
But then, I typically over engineer my projects in self defense.
Pat
EddieWalker
Epic Contributor
I find it just about impossible to believe that nails are sufficient for holding the headers onto the sides of the posts on there own. My understanding is that nails are never to be used alone to support load bearing members of a structure. I've never seen it done and would never do so myself.
In my opinion, carriage bolts are the only way to go. I would use three half inch, hot dipped galvanized carriage bolts on each post as a minimum. First, tack on the 2x12's with nails to hold them in place after they are level. The drill your holes and install your bolts.
As for the depth of the posts, I would go 3 feet or more. It would depend on the soil and movement of the soil during the year. In some places, 4 feet would be the minimum. I've heard of areas of the country where that's not even deep enough.
Good luck,
Eddie
In my opinion, carriage bolts are the only way to go. I would use three half inch, hot dipped galvanized carriage bolts on each post as a minimum. First, tack on the 2x12's with nails to hold them in place after they are level. The drill your holes and install your bolts.
As for the depth of the posts, I would go 3 feet or more. It would depend on the soil and movement of the soil during the year. In some places, 4 feet would be the minimum. I've heard of areas of the country where that's not even deep enough.
Good luck,
Eddie
Bolts and Lags,
This poses another Engineering feat that must be taken into account prior to the fact. Nails are small in diameter, where as bolts and lags are not, thus could potentially weaken truss members.
Any larger diameter fastner could pose a problem and should be checked into before hand. Especially if these come near a joint and or truss plate.
Its funny because a nail can puncture a plate and be fine PROVIDED it doesn't cause the plate to tear and or pull away from the wood but cutting or drilling is strictly prohibited in most cases.
This poses another Engineering feat that must be taken into account prior to the fact. Nails are small in diameter, where as bolts and lags are not, thus could potentially weaken truss members.
Any larger diameter fastner could pose a problem and should be checked into before hand. Especially if these come near a joint and or truss plate.
Its funny because a nail can puncture a plate and be fine PROVIDED it doesn't cause the plate to tear and or pull away from the wood but cutting or drilling is strictly prohibited in most cases.
yooperdave
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If you are buying your shed from a 'professional' company, you have the right to demand the structural calculations to PROVE structural adequacy.
Frost depth is frost depth. If the building code requires a certain depth, then hold the company accountable to give you what the building code specifies. You are correct that embedment depth of the pole provides much of the structural integrity of the lateral system of the building.
Big picture: This is a small and low eave height shed - it should not take much to bring this structure into code compliance.
Good Luck,
Yooper Dave
Frost depth is frost depth. If the building code requires a certain depth, then hold the company accountable to give you what the building code specifies. You are correct that embedment depth of the pole provides much of the structural integrity of the lateral system of the building.
Big picture: This is a small and low eave height shed - it should not take much to bring this structure into code compliance.
Good Luck,
Yooper Dave
GE222
Gold Member
I spec'd the design of a 42 x 48 shed along with Lester Buildings in Southern Wisconsin.
It was built on a concrete slab versus having the poles cemented in the ground below the frost line.
After 4 years, there have been no issues with the slab settling or cracking.
I started with a good rock/clay base under the slab. It was graded with a Cat D-6 and allowed to settle for several months before the slab was poured.
Limestone was added and then compacted.
The slab itself was roughly 18" thick by 24" wide at the perimeter. The base was tapered up for an average thickness of 5.5".
Rebar was installed at the perimeter, mesh on everything, and fiberglass was included in the mix.
A 1.5" PVC pipe was buried prior to the pour for the main electrical service.
The finished shed has 14" sidewalls with windows, and a 16' x 12' overhead door at each end.
The finished height of the slab is about 12-14" above the local grade for excellent water drainage.
I will probably never have to worry about rotting sill plates, posts, or the tin corroding on the bottom.
The posts are also 8' on center so I can easily add internal sheathing without piece together panels.
Would I ever do it this way again? Yes, Yes, Yes!!!
It was built on a concrete slab versus having the poles cemented in the ground below the frost line.
After 4 years, there have been no issues with the slab settling or cracking.
I started with a good rock/clay base under the slab. It was graded with a Cat D-6 and allowed to settle for several months before the slab was poured.
Limestone was added and then compacted.
The slab itself was roughly 18" thick by 24" wide at the perimeter. The base was tapered up for an average thickness of 5.5".
Rebar was installed at the perimeter, mesh on everything, and fiberglass was included in the mix.
A 1.5" PVC pipe was buried prior to the pour for the main electrical service.
The finished shed has 14" sidewalls with windows, and a 16' x 12' overhead door at each end.
The finished height of the slab is about 12-14" above the local grade for excellent water drainage.
I will probably never have to worry about rotting sill plates, posts, or the tin corroding on the bottom.
The posts are also 8' on center so I can easily add internal sheathing without piece together panels.
Would I ever do it this way again? Yes, Yes, Yes!!!
flusher
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Your pole barn is pretty close in size to the 20x28x10H (front),9H(rear) pole frame equipment shed I built last year (metal sides and roof). I used Simpson T and L connectors and 1/2" bolts/nuts to tie the 4x12 beams to the tops of the 4x6 P.T. posts. I needed doubled 2x12s (=4x12) to span 14 ft between two rows of posts. The posts in third row in the rear were on 7-ft centers so I used 4x10 beams.
Used a lot of 4x4 knee braces with 1/2x6" lag bolts to stiffen the frame.
