new sawmill shed

[cheyenne]

evening all! i'm in the planning stages of a shed for my new sawmill & i know i can never build it big enough.my thoughts are 60' long+ & probley 20' or 24' wide. i was thinking pouring a monolithic slab and building everything on the slab. NOW i want to clear span 30' on one side for the mill & log deck. i was thinking bolting 3x12s together, maybe putting in 1/4x12 steel between the 3x12s. needless to say i'll mill my own timbers after i set the mill on the slab and build around it. lifting & setting is no problem i have heavy iron. i'm in upstate n.y. lots of snow so metal roof. I look forward to your ideas. cheyenne

[moonhill]

How high are your walls going to be?  This will have an impact on the truss you may need to span the 30'.  My mill building is 60' long and 30' wide and 16' to the tie beams. It's tight getting the 4x4 forklift in and picking off the track.  It's almost true "you can never build it too big".  It's more likely on the small side.  What's the future going to bring, an edger maybe, that happened to me and I lost more space.  Are you using a fork lift to handle material?   I have a multi king post truss over my spillway, 26'-6".    Tim

[cheyenne]

i'm only going to cut for my own use my business days are over thank god. wall height over the clear span  10 or 12' rear wall 8' 0r 10' pitched shed roof with metal. i'll load with a skid steer with forks onto a log deck. thinking 6x6 posts & header in the center end to end to help carry the load. cheyenne

[jfl]

I also tried to design a sawmill shed and had a few problem with the main beam where the unsawn log go through.

First problem: my sawmill is 21 feet long.  I can cut lumber up to 18 feet long. I want the openning to be 25 feet wide: how can I get 25 feet long pieces from a sawmill that can only cur 18 feet long pieces.  I'll get back on that later.

You asked if bolting 2   3x12 together would do.  What spiecies are they? Their strength varies with the spiecies and the grade.  Let's say that you use canadian SPF #2.  Bending Strength is 875 psi (from www.cwc.ca).  From tables, I see that a single 3x12 can support 1318 lbs with a Fb=900 psi.  So for 875 psi we get:

W=1318lbs*875/900 = 1281 lbs.

If you put 2 of them together, you'll get twice the strength, so 2562 lbs. 

Now what is the load? Normally, you would divide the load on the roof (dead+live) between the various supports.  Let say that the shed is 24x10.  So each 24 beam support half the load of the roof, so 5 x 24. If you use metal roof (with a high enough pitch so no snow can stay on the roof), you can neglect the snow load. You would have to estimate what will be the effective weight of the material on the roof (rafter+metal).  Let's say 10 dead + 10 live: So the weight on the beam would be:

5 ft x 24 ft x 20 lbs/sqft = 2400 lbs.

So the load is less than the capacity of the 2 beams so that would work.  I don't know how composite (metal + wood) would behave: I'm also building around my land with my own wood, but the thing that grow here is mostly wood: I don't get many metal tree so... ;D

WARNING: Here are the assumption I used in the calculations above, if any assumption doesn't apply to your case, then the end result doesn't apply either:

A) wood: Canadian SPF.  Don't you say you wanted to mill your own? What speicies?
B) grade: #2.  I can't tell you how to grade your lumber.  There is a grading document on www.nelma.org.
C) load: what are the actual dimension of the roof  where the 24 foot beam will be.
D) slope: even with metal roof, there must be enough slope for the snow to fall.  If I remember right below some angle (something like 25 degrees) all the snow stay on the roof. Above another angle (something like 60 degrees) no snow stay on the roof.  And in between, the load goes linearily from all the load to no load depending on the actual angle. So maybe you have to include a snow load in the calculation.  On the other side, when you add the snow load, you can increase the strengh of the wood (Fb) by 15% because of the duration of the snow.
E) this is a pretty long beam. You have to make sure that it will not buckle. You have to make sur it will not rotate on its extremities. Also it has to be laterally supported on all it's length.  There are ways to compute a beam stability factor which will affect the Fb (I used 875 psi) depending upon how the beam is attached to the rest of the structure.

I mentionned previously about the fact that a mill can't cut long enough to cover itself completely:  I solved that issue by using a truss. In a truss all the member are working in compression or in tension, not in bending, so you can make a connection between 2 lumbers, as long as the connection is stronger than the compression or tension load.

jf

[Don P]

I'm confused, I was reading that the beam has a span of 30' and is supporting half of a series of 24' roof trusses that run down a 60' building.
Assuming a 30 psf snow load, NY varies alot, this should be checked with the local building department.
If the truss has a 1' overhang then the portion of the truss bearing on the door header is 13' wide X 30' long X 40 pounds per square foot (snow plus dead load of the roof)= 13,600 lbs uniformly distributed on the 30' long header  ???

[thecfarm]

jfl,on cutting wood longer than the mill,go to Forum Extras,upper right hand side,this will bring you to Knowledge Base,click on to Milling Bandsaw,look for Sawing Logs Longer Than Mill.You are a new member and probaly don't know about this.Good luck.

[Meadows Miller]

Gday

Im making the main beams for my sawmill shed out of 3 Bolt laminated beams with 16"x2 stock on the outside and a 16x4" in the center 3 pices wide giving me a 16x8" beam to span 31'6" on the 3 bays on the front of the mill shed ill be milling timber beams upto 28'long somtimes for my Dads log home buisness Ive thought of using log but prefer sawntimber the posts will be 10"x10"s 15'high  I know the pine beams will weigh 350 kg 770lbs when there dry but if Im building somthing  I usually Over build it  :D the outside joins will be plated with 12"x 1/4 3 foot plates on each side the shed will be 95' x 28' this shed is still in the planing stage so that could change
 
Heres a rough idea of what they will look like from the top  .the open ends in the middile will  be mated with a 4" tennon on the top of the post and take the top of the long leg brace .

________________________________________________________________
l________________________________l_______________________________l
____________l_________________________________________l__________
l________________________________l_______________________________l

reguards Chris

[Raphael]

I'm leaning towards a design that puts the big opening on a gabled end.
Takes the dead load off that header (unless it's supporting a second floor).

[moonhill]

Raphael, it also keep the snow coming off the roof to a minimum.  That is my biggest problem in the winter.   Tim

[cheyenne]

Raphael, that is a very good idea. Now i'm thinking a Gambrel roof with trusses for storage above. With a shed roof for the other 30'. The more i ponder the bigger this thing gets. Think i'll ever get it built. thank you Cheyenne

[Raphael]

The more i ponder the bigger this thing gets.

I know how that works, my barn design keeps threatening to expand beyond the legal setback.  :D :D