Rough cut lumber

[ww_kayak]

A couple of question about rough cut lumber. If I cut and dry TRUE two-by-X's, should I just use a standard lumber span table and know that I'm stronger than I need to be, or can I safely take adavantage of the bigger dimensions? I want to design a garage/shop and I'd to get as wide as possible with conventional building techniques( no trusses or engineered joists)? I have 40+ acres of Eastern Hemlock and a 30" band saw mill...

The town has no problem with native timber, and doesn't even require actual plans for the garage. I just want to design within a safe range before I have it checked out by an architect.

Thanks

[Sweep]

An architect will not design the structure from building code tables, but by calculating the section modulous and moment of inertia of whatever lumber the mill will produce. There's even a website that will calculate those values for any cross-section. The difficulty will be in determining the maximum allowable fiber stress (Fb) and modulous of elasticity (E) for the wood and how much safety factor to use for possible grading errors.

Why would you wait to give it to the architect? You aren't going to get any relevant answers until you do. Structural design of a simple structure is not difficult but it isn't intuitive either; you need to do the math. If the architect intends to put his/her name on the design, the buck stops there so the opinion of others is irrelevant.

Now, if your architect needs advice, let me know.

[ww_kayak]

I guess I want to get some ballpark figures. I can tell him I want a 40 foot wide bay with 16 foot ceilings, and he'll design it. I was just looking for some general advice. Something like " jeez anything over X feet I wouldn't use conventional building techniques." That way I don't waste his time and my money redesigning my design :0. Plus I've read enough on this forum to know there is a big difference in what an architect designs and what a contractor knows works :-)

[Sweep]

It appears that you are assuming that a contractor's intuition derived from his long experience using dimensioned lumber sized from the building code tables would give you a more efficient design for your rough sawn lumber than a design based on the actual structural capacity of the wood.

You could not be more wrong. I have been designing buildings for 40 years and have found that intuitive design is nothing more than guessing which is a waste of time and money.

Tell the architect the maximum practical size of the lumber you intend to cut and its species and grade. In ten minutes the architect will tell you to the inch the maximum uniformly loaded simple span for that member for various spacings. If double those spans is not big enough for you, then you will need an intermediate support or a truss. Why would you need to guess?

But how could I know what actually works; I'm only an architect. :roll:

[Joe Bartok]

There's even a website that will calculate those values for any cross-section.
Sweep: Can you post a link to this site?
I've been scouring the Internet for the past year, looking for a calculator that will return First and Second Moments of Area, Area, centroid, etc., for irregular sections.

[Sweep]

Joe, here it is:

http://www.engineersedge.com/section_properties_menu.shtml

[Joe Bartok]

Sweep, thanks for the link. It's not exactly what I've been looking for but still handy.
What I'm been after is a calculator where I can draw any section to scale, trace the perimeter and the program returns the values. Such a program would be handy in the analysis of log sections where material has been removed to accommodate purlins or ridges. Currently I'm analysing these variables for rotated circular sections and triangles, and then finishing the final math by hand. A somewhat tedious process! I think I can make my own irregular section calculator with javascript anyway ... back to the drawing board.

[ww_kayak]

Sorry I asked. I had no intention of guessing, or waiting to talk to an architect, I was just wondering if anyone had some thoughts or opinions on the subject. I guess it's not that kind of forum, thanks anyway.

[Sweep]

Try the Journal of Light Construction forum

http://forums.jlconline.com/forums/index.php