(Another) Sawmill shed design thread, but I could use some help

[AnthonyW]

Yes, I am starting another sawmill shed design thread. I can't find the one I was using, nor can I find the thread with the calculator I'm interested in.

I'm interested in building a shed similar to bruce29's in https://forestryforum.com/board/index.php/topic,56866.80.html post #82 or https://forestryforum.com/gallery/displayimage.php?album=3208&pid=123252#top_display_media.

I must keep the shed under 200 sq ft so I thinking 10'x20', with one side open for 20' and the other 20' side having a single post at the center. The roof is driving the other portion of the design. The roof panels are 3' wide and either 12' or 8' long. Referring to bruce29's shed, I will have a long slope of 12' and a short steep slope of 4' (8' cut in half, or 12' cut in thirds). The roof will be 21' or 24' wide, thus overhanging either 6" or 24" beyond the corner posts. I am also looking to use a 5/12 pitch. On my current storage shed, the 5/12 pitched metal roof sheds snow fairly well.

I'm not sure I trust much of the lumber (eastern white pine) I can mill myself in terms of grade and strength. I'm thinking of purchasing 4x4 PT for posts, and 2x material for the front and rear beams. The rafters and such I don't have a problem using milled material.

I have run into two problems/questions so far.

1) For the 10' spans in the back, I had found but now have lost a calculator for determining which 2x I should be using. The calculator had a selection for 2-2x6, 2-2x8, 3-2x8, etc. and you entered the span and loads. (P.S. per the state documents, the snow load in my area is 55PSF). Anyone know of a calculator like this? Perhaps a link?

2) For the open 20' span in the front, the "ridge" board will be directly above the front posts and 50" higher than the rear posts. I was thinking of a two-for-one to accomplish the span and (part of) the height difference by building a wooden floor truss. Are there any calculators or design tools out there to help me with this?

A feature I do not see in bruce29's shed are any 'ceiling joists', only rafters. It also appears that his roof pitch is lower than mine. With an 60" total height difference in my shed (5/12 pitch over 12'), I think they are required.

I'm working on a sketchup layout and hope to post it soon.

[Raider Bill]

I'd feel better using at least 6x6"s or phone poles for posts.

[AnthonyW]

I found these two calculators (but not the one I'm looking for yet)

http://www.awc.org/calculators/span/reversecalc/reversecalc.asp

http://www.awc.org/calculators/span/calc/timbercalcstyle.asp

For a given species of lumber they calculate the maximum span for a given size or given the size calculate the maximum span.

I found a set of tables at http://constructitall.com/9-uncategorised/972-maximum-span-calculations-for-joists-a-rafters.html that has the information I am looking for, but I know I came across a calculator somewhere.

[AnthonyW]

I finished my sketchup drawing for the shed.



The corner posts are 10'x20'. The overall length is 24'. The height is dictated by the roof pitch (5/12) and the distance from the ground to the bottom of the roof rafter in the rear, 7 feet. With the bottom of the roof rafter at 7', the rear posts are, coincidentally, at 7'-2" (10" up for the 5/12 pitch and 8" down for the 2x8 beam).  The bottom of the "ridge beam" is just about 12' (7' plus 5/12 pitch * 12 feet).

I called around looking for pricing/specs on the floor truss I was thinking of using to span the opening but I couldn't get pricing. I did however get pricing on an LVL. The LVL was 16" tall by 24' long and either 5 1/4" thick or 3x1 3/4" thick either way the bill was over $700. This plan isn't going to happen.

I was planning on adding some corner bracing to stiffen the shed. But I realized the only reason to have the large front opening is to be able to load logs. Is it possible to add corner braces (gussets?) in such a way as to take some of the ridge load and shorten the span? If I started the brace around 7' on a 45* angle, it could shorten the span by 3'-4' on either side, reducing it to 12'-14'.



I added one brace in the front left, highlighted in orange.

[BCsaw]

I would be worried about using 4x4's. Your asking a lot from them. Also a cross beam on the ends and add braces from them to the corner posts would stiffen up the frame a bunch.

My 2 cents......good luck with your build. ;D

[AnthonyW]

I didn't update the posts in the drawing. Most likely the front posts will be 6x6 to compensate for the "missing" post in the middle. I figure just butt joint or face screwing the corner braces in place will only stiffen the frame but won't take any of the roof load. Now I trying to determine what technique is the right one to transfer some of the roof load to the corner post so I can shorten the span and reduce the size of the header.