Sawmill Shed Pole Building

[TimW]

I'm gonna build me a sawmill shed.  It is all in the planning stages right now.  I am thinking 40 x 60 feet.  But it might be smaller.  6x6 poles every 10 feet on the sides.  The trusses will be 40 foot wide and premade.  I already got a quote on them.  I build without prints, just what is in my mind.  It worked well that way on my 44x30 foot pole barn.

Two items that I am not clear on.  My top sill plates that the trusses sit on is one I am not clear on.  On my pole barn, I just bolted 2x6s on both sides of the pole.  Then I decided to stack another 2x6 under both sides.  This has worked well with a 20 foot truss span.  But I am not sure if 2x12s on both sides of the posts will work here, supporting 40 foot wide trusses and roof.

 

 

The 2nd item that I am not clear on is,.......I would like to have side doors on each side that would be 16 or 18 foot wide.  I can add bracing to reduce the load on the top sills, as they don't need to be clear span higher up.  Will 2x12s on both sides be enough to support the truss, which will be on 5 foot centers (every other truss will sit over the poles) with 2x4 purlins spaced 2 foot apart, followed with 22 guage metal?

[Don P]

Let's see if we are on the same page. This is a 40x60 footprint. I've put an 18' doorway on what I call the side to make sure we are calling the same thing the "side" vs the "end", good so far?



 

[TimW]

Let's see if we are on the same page. This is a 40x60 footprint. I've put an 18' doorway on what I call the side to make sure we are calling the same thing the "side" vs the "end", good so far?

Don,
Yes, the ends will be open and the 18 foot door will be on the side.  But I will have another 18 foot door on the other side too.
        

[Ljohnsaw]

 :P

[firefighter ontheside]

I take it there is no building code to worry about in your area.  I build small buildings under the radar, but something that big I would have to go thru the building department for our county.  I know you're in Texas, but do you get snow?  

[doc henderson]

how tall on the walls, and how tall do you want your door openings.

[Don P]

One step at a time. Engineering on large buildings is always prudent, well, any building really. Wall height gets into bracing so well worth thinking about.

That gives us enough to go on for sizing the plates. You have basically 2 conditions going on.

The first is the "regular" 10' spaced posts with a truss landing on the posts and a truss landing at midspan between posts. Half the truss is bearing on the plate on one side, half is bearing on the plate on the other. I'm going to assume there is a 1' overhang on each side as well, so 21' of truss span bearing on each plate. Truss spacing is 5' so the truss is carrying 2.5' of roof on each side of it, 5'. 21' x 5'=105 square feet of tributary area bearing on the plate. The load is 20 pounds per square foot live load (wind) + 10psf dead load (roof material weight)=30psf. 105 square feet of area x 30 pounds per square foot load=3150 lbs load landing at midspan on the plate, so use this calc;
https://forestryforum.com/members/donp/beamclc_ctrpointload.htm
I'm going to give you the allowable adjusted design values for #2 SYP to plug in;
Fb 1078, E 1.4, Fv 219
I'm coming up with a triple 2x12 nominal, store bought dimensions (1.5 x 11.25") or a double full dimension 2"x12"

Second condition;
The 18' opening uses a different calc;
https://forestryforum.com/members/donp/2ptbeam.htm
What I'm assuming here is that the trusses land at roughly the third points of span. If a truss lands in the center section of span the bending moment gets Much worse and we need to revisit this, so bear that in mind.
A triple full dimension 2x12 fails. I'm going to juice the numbers and go deeper. At #1 Fb, bending strength, goes to 1437psi, E, elasticity, goes to 1.6. I get a pass at 5.5 x 14". Not loving that though.
Lets see what LVL's do, Fb 2800, E2.0, Fv280
They can come as 1-3/4" thick x 11-7/8 deep so a double is 3.5 x 11.875 and I get a pass, that would be my choice over the doors. The supplier can run a check on those, typically the truss shop can do all that, supply them with the truss package and supply connectors.

That is one way. What we've just checked there is gravity loads, vertical, on the plates. Bearing area of the trusses on the plates needs to be confirmed and the gorilla in the room is wind bracing, that is a big sail, but lets see how this shakes out first.

[doc henderson]

would it help to add dedicated posts on each side of the door, breaking up the post every 10 feet? so the header across the door opening has a post?

[doc henderson]

oops, I see you did that in the drawing.

[TimW]

how tall on the walls, and how tall do you want your door openings.

Snow?  What's that?  The Panhandle (can get blizzards) and North Texas get snow.  If we get any, it melts within a few hours.  Usually melts upon hitting the ground.  We're an hour north of Houston.  Better chance for a hurricane than snow.

[TimW]

how tall on the walls, and how tall do you want your door openings.

I haven't decided yet.  The barn has 13.5 foot tall walls.  I might go 10 foot walls.

[TimW]

One step at a time. Engineering on large buildings is always prudent, well, any building really. Wall height gets into bracing so well worth thinking about.

That gives us enough to go on for sizing the plates. You have basically 2 conditions going on.

The first is the "regular" 10' spaced posts with a truss landing on the posts and a truss landing at midspan between posts. Half the truss is bearing on the plate on one side, half is bearing on the plate on the other. I'm going to assume there is a 1' overhang on each side as well, so 21' of truss span bearing on each plate. Truss spacing is 5' so the truss is carrying 2.5' of roof on each side of it, 5'. 21' x 5'=105 square feet of tributary area bearing on the plate. The load is 20 pounds per square foot live load (wind) + 10psf dead load (roof material weight)=30psf. 105 square feet of area x 30 pounds per square foot load=3150 lbs load landing at midspan on the plate, so use this calc;
https://forestryforum.com/members/donp/beamclc_ctrpointload.htm
I'm going to give you the allowable adjusted design values for #2 SYP to plug in;
Fb 1078, E 1.4, Fv 219
I'm coming up with a triple 2x12 nominal, store bought dimensions (1.5 x 11.25") or a double full dimension 2"x12"

Second condition;
The 18' opening uses a different calc;
https://forestryforum.com/members/donp/2ptbeam.htm
What I'm assuming here is that the trusses land at roughly the third points of span. If a truss lands in the center section of span the bending moment gets Much worse and we need to revisit this, so bear that in mind.
A triple full dimension 2x12 fails. I'm going to juice the numbers and go deeper. At #1 Fb, bending strength, goes to 1437psi, E, elasticity, goes to 1.6. I get a pass at 5.5 x 14". Not loving that though.
Lets see what LVL's do, Fb 2800, E2.0, Fv280
They can come as 1-3/4" thick x 11-7/8 deep so a double is 3.5 x 11.875 and I get a pass, that would be my choice over the doors. The supplier can run a check on those, typically the truss shop can do all that, supply them with the truss package and supply connectors.

That is one way. What we've just checked there is gravity loads, vertical, on the plates. Bearing area of the trusses on the plates needs to be confirmed and the gorilla in the room is wind bracing, that is a big sail, but lets see how this shakes out first.

Thanks Don.  I had planned on 2 foot eves, but that doesn't show on the truss quote.
I will go with full dimension 2x12s.  One on each side of the pole.  Will four 1/2" bolts be enough to support them on the pole? Or go 3/4"?
For the 18 foot wide openings, can I just install 6x16 SYP beams?  I can get them for free. LVLs, not free.  Can I use diagonals braces off the poles to help support the door opening sill plates?
Wind bracing is a must, as wind uplift is big down here.  On my barn, I used 2x6s diagonal on the insides of the poles at each corner and 2x6 purlins on two foot vertical centers outside the poles.

[Don P]

6x16, yes ma'am, that'll pass.
I wouldn't hang on bolts, I'd notch the 2x12's in on either face. Between the wall girts (your wall "purlins") at the upper set run a vertical 2x6 on the post to help capture the 2x12's and bolt that through the post below the beam and then through the beams and post "tenon".

Diagonal braces will help with wind at the openings, and everywhere else you can put them. It is not considered good practice to count on them for reducing beam dimension or span. I know everyone wants to do that but I have asked the question of several engineers. It certainly doesn't hurt a thing  ;).

I do like Docs idea of double posts at those doorways with the 2x12's on the main posts and the 6x16 on shorter posts to support the 6x16, bolt or lag the posts together. I'm still getting a pass at a 19' opening if you go that route. Use good wood for those, there's no redundancy there.

Doodling;


 

 
Actually when all that lays out even spaced with Doc's inboard door posts, the opening scales to 18' 5-11/16"

[TimW]

6x16, yes, that'll pass.
I wouldn't hang on bolts, I'd notch the 2x12's in on either face. Between the wall girts (your wall "purlins") at the upper set run a vertical 2x6 on the post to help capture the 2x12's and bolt that through the post below the beam and then through the beams and post "tenon".

Diagonal braces will help with wind at the openings, and everywhere else you can put them. It is not considered good practice to count on them for reducing beam dimension or span. I know everyone wants to do that but I have asked the question of several engineers. It certainly doesn't hurt a thing  ;).

I do like Docs idea of double posts at those doorways with the 2x12's on the main posts and the 6x16 on shorter posts to support the 6x16, bolt or lag the posts together. I'm still getting a pass at a 19' opening if you go that route. Use good wood for those, there's no redundancy there.

Doodling;


 

 
Actually when all that lays out even spaced with Doc's inboard door posts, the opening scales to 18' 5-11/16"

Yeah girts.  That was a senior moment.  I follow your description.  It is all clear in my mind now.  Thanks Don and Doc!  Glad I cut extra 6x6 poles.  These side doors will mainly be for moving lumber pallets in or out.  Bracing all 6x6s will be done also.  That won't be a problem, just more wood.
As it gets built, I will decide to close one end or not.  The other end will be for moving logs to the mill.  But with the amount of trees I have around here, I have perfected the art of moving 20 foot logs thru 14 foot openings.

[TimW]

On second thought, I will put 6x6s and diagonal bracing on one end.  Not sure about enclosing it yet, as I really want airflow.

Also, I will add 4x6 blocks between the 6x6s where the truss won't be supported by a 6x6.  Like on my barn here.

 

[Don P]

Hmm, several thinking problems on my end.
First, there are 3 trusses on the header over the door, one at midspan, one at each quarter point.
Second, I checked the 6x16 beam still using the dimensional lumber design strengths rather than switching to the heavy timber design values.

Always, rethink, check yourself, own mistakes, and fix it. Here we go.

There are a few ways of looking at the 3 point loading but the long and short of it is the maximum bending moment is higher than I figured above for the 2 point load which was 19,425 ft-lbs. We have more load, one more truss. And our "hand" moved out further on the torque wrench, he have more leverage bending the beam. You're a A&P mech, one way I think about these numbers, a beam is nothing but 2 torque wrenches with the handles welded together.

The easiest equation for this is .5 x P x L
.5 x #3150 (ea truss load) x 18.5'(header span)=29,138 ft-lbs

Backing into this a different way, check the maximum flexural stress of the bottom fiber of the 16" beam= Max moment (in/lbs)/ section modulus
The equation for section modulus= bd²/6 = 6 x 16²/6 = 256"³
So, f= (29,138 x 12)/256= 1366 psi required Fb in the beam material

I did that kind of backwards of how we've done that in the past but it shows another way of looking at a problem. Now we know the Fb required and I'll go to the heavy timber tables in the NDS and see if the SYP checks out....
Hmm, #2 is Fb 850psi, not even close
#1 is 1350 psi, mighty close
#1 dense is 1550 psi well clear.

#1 is smaller knots <4", well centered, away from the edges, straight grained 1 in 10 max, nice material. #1 dense is at least 6 rings per inch and at least 1/3 summerwood, can you hit that?


While I'm backchecking... here's another way using the calcs here. For 3 evenly spaced point loads you can multiply the individual point load x 4 and plug that into the total load input and use the heavy timber uniform load beam calc here;
https://forestryforum.com/members/donp/beamclc06b.htm
punching in our inputs I'm getting maxmoment of 29,137.5 ft-lbs, check
#1SYP- minor fail in bending, #1 dense easy pass

[TimW]

Hmm, several thinking problems on my end.
First, there are 3 trusses on the header over the door, one at midspan, one at each quarter point.
Second, I checked the 6x16 beam still using the dimensional lumber design strengths rather than switching to the heavy timber design values.

Always, rethink, check yourself, own mistakes, and fix it. Here we go.

There are a few ways of looking at the 3 point loading but the long and short of it is the maximum bending moment is higher than I figured above for the 2 point load which was 19,425 ft-lbs. We have more load, one more truss. And our "hand" moved out further on the torque wrench, he have more leverage bending the beam. You're a A&P mech, one way I think about these numbers, a beam is nothing but 2 torque wrenches with the handles welded together.

The easiest equation for this is .5 x P x L
.5 x #3150 (ea truss load) x 18.5'(header span)=29,138 ft-lbs

Backing into this a different way, check the maximum flexural stress of the bottom fiber of the 16" beam= Max moment (in/lbs)/ section modulus
The equation for section modulus= bd²/6 = 6 x 16²/6 = 256"³
So, f= (29,138 x 12)/256= 1366 psi required Fb in the beam material

I did that kind of backwards of how we've done that in the past but it shows another way of looking at a problem. Now we know the Fb required and I'll go to the heavy timber tables in the NDS and see if the SYP checks out....
Hmm, #2 is Fb 850psi, not even close
#1 is 1350 psi, mighty close
#1 dense is 1550 psi well clear.

#1 is smaller knots <4", well centered, away from the edges, straight grained 1 in 10 max, nice material. #1 dense is at least 6 rings per inch and at least 1/3 summerwood, can you hit that?


While I'm backchecking... here's another way using the calcs here. For 3 evenly spaced point loads you can multiply the individual point load x 4 and plug that into the total load input and use the heavy timber uniform load beam calc here;
https://forestryforum.com/members/donp/beamclc06b.htm
punching in our inputs I'm getting maxmoment of 29,137.5 ft-lbs, check
#1SYP- minor fail in bending, #1 dense easy pass

Uh, with posts on 10 foot centers and trusses on 5 foot centers,...1 truss in the middle span and a truss over each post.  I don't understand where you got ...1 at each quarter point?
The door posts will be doubled up, so.............oh, I see now.
The posts supporting the trusses will have to be on 10 foot centers and the door opening needs to be reduced to 18 feet. That moves more trusses off of posts about a foot. 
But the double posts don't need to be side by side.  The inner post can be moved in to span 18 feet and leave the outer posts on 10 foot centers.  That puts a foot between the double posts.  Then stack the 6x16 and the 2x12s on the posts as mentioned previously.
        Happy Thanksgiving

[Don P]

Here's how I'm seeing the truss layout. The trusses are point loading 3150 lbs each at ~1/4,1/2 and 3/4 of the door beam span;



The apple pie is gonna have to wait, I'm turkey damaged  :D

[TimW]

Here's how I'm seeing the truss layout. The trusses are point loading 3150 lbs each at ~1/4,1/2 and 3/4 of the door beam span;

A picture is worth a thousand words.  Thanks.

[Don P]

I need to amend the grading there. The 6" face cannot have a centerline knot larger than 1-1/2" or an edge knot larger than 1", but I would avoid edge knots altogether.

Furby sent another idea this morning, need to do a little cyphering and sketching but need to go be moleman under a house while the day is warm.

[TimW]

Thanks Don.  Pretty sure I can get grade needed for this.  I have been eyeing this pine for a special occasion.

   Neighbor said I can take it down.  But I dig them and push them over.  Bye bye stump.

[Don P]

Wow, that's a honker and looks like at least 20' to the first kink.
Furby was asking about doubling or tripling up the trusses on each side of the door and then running purlins the 18' way to avoid such a big header. That would work but at 18' the purlins would need to be 2x10's. Just another way.

Looks like I'm a welder tomorrow, I think today qualified as skid steer abuse. Bruno would fire me for sure  :D.

[TimW]

Wow, that's a honker and looks like at least 20' to the first kink.
Furby was asking about doubling or tripling up the trusses on each side of the door and then running purlins the 18' way to avoid such a big header. That would work but at 18' the purlins would need to be 2x10's. Just another way.

Looks like I'm a welder tomorrow, I think today qualified as skid steer abuse. Bruno would fire me for sure  :D.

That honker is over 100 feet tall.  Those white posts are 5 foot and the jon boat is 14 feet.  It's around 60 feet to the first limb.
Who is Furby?    I don't see how not having a truss for 18 feet will work.  An 18 foot purlin?  Is that flat or on edge?  It won't work flat as it would be like a diving board.  It won't work on edge, as the knotch to fit the rest of the purlins will only be 2 inches thick.
Not to even mention how long diagonal braces across that 18 feet would have to be.
I think the trusses should all be on 5 foot centers as I am fine with the 6x16 header. 
I like the idea of 6x16s beams as headers, as I excel at the difficult.  I like challenges. 
Or as Barney (How I Met Your Mother) would say, "Challenge accepted".

[btulloh]

Besides, a 6x16 20ft long is one honkin' piece o' wood and should be quite a conversation starter. 

Always fun to watch these builds unfold. Thanks for keeping us in the loop. 

[TimW]

Besides, a 6x16 20ft long is one honkin' piece o' wood and should be quite a conversation starter.

Always fun to watch these builds unfold. Thanks for keeping us in the loop.

btulloh,
Welcome aboard!