Spruce and Fir Questions

Hi all - Im looking for comments pertaining to using either Engelmann Spruce or Coast Douglas Fir for home timber construction. Im located in western Colorado and I can purchase large dimention timbers in these species. Im from back east and really dont know much about the structural qualities of these species. I am also looking for design values for these same species. Any comments will be most helpful -- Thanks !!

Personally, I have found the TFG Design and Joinery Handbook invaluable - the handbook includes a set of tables showing design values (modulus of elasticity, etc) for various species. Great resoure for comparison and for use in calculation of beam sizes required for various species. Always good to have an engineer/architect do a "reality check" on your selections. See the TFG book store for ordering- cost $25 and well worth it.

Ok TFG.....where is my commission check?

Both are great framing materials. Spruce is less stiff than Douglas Fir , but available "locally" for you. You will have to use larger members and more of them but that is the fun of timberframing.
DF #2 Fb 875 Fv 85 E 1,300,000
S #2 Fb 600 Fv 65 E 1,000,000
Values from NDS '97
Bake

I have to apologize for my post reply to the original question. After looking through the TFG Design handbook this weekend, I realize this was NOT the source I have used in the past for structural comparison of various species. I actually had a photocopy from another source attached in my book. If/when I find where I got the photocopy from, I will post that info.
Again, hope I did not mislead and I will send back the commission check from TFG.

Roger,

Maybe you used the tables so much they fell out and you had to clip them back in! I just checked my Guild Joinery and Design Workbook (V3.0 1998) and the tables begin on page 29 and continue to page 33. Same values as Bake gave us from NDS are shown.

Remember values are not identical for timbers used as "beams and stringers" as they are for ones used as "posts and timbers".

Rudy

Rudi,

I think that I understand the meaning of the words "post" and "beam" and I might even just stretch to "stringer" but what is a "timber".

I have learned the hard way that the same words mean different things to different people.

Ken Hume http://www.clik.to/WorldofWood

"Timber" is what the lumber jack yells as the tree is falling from the stump. :-)

Rudi, thanks greatly for the catch! You are absolutely correct - I guess I should have double-checked as the only times I am usually wrong is when I thought I was wrong!
Actually, this has been happening quite a bit since I turned 40......now, where did I lay those dentures....hmmmmmm.

"Beam and stringer" and "post and timber" are designations for the cross sectional dimensions of heavy timber memebers. A "beam and stringer" cross section has a depth that is more than 2 inches greater than its width. The piece is expected to be used mainly in bending. A "post and timber" cross section has its depth within 2 inches of its width. It is primarily intended for use in compression. The grading standards vary for the two designations, hence the design values also differ.

Dick,

I am now really glad that I asked that question. This is all news to me.

If I have a deep brace which is 4" wide x 8" deep and it is primarily intended to work in compression and / or tension but not bending, how is it classified ?

Post and timber ?

Regards

Ken Hume

I thought a timber was a minimum of 5"x5" John.

Right. If both dimensions of the cross section are 5-inches or greater, then the classification of "beam and stringer" and "post and timbers" applies. You can use a "beam and stringer" in compression or tension if you want. Likewise you can use a "post and timber" in bending. The point is that the grader looks at the pieces differently (with respect to defect type, size, and location) and the individual pieces have different design values. A 4x8 falls under the "dimension lumber" classification -- yet another set of design values.

Dick,

Is there a web site where I can check out the dimensioned lumber values or do you have the name of the full publication so that I can purchase it ?

Ken Hume http://www.clik.to/WorldofWood

The specification of the categories and the design values for both dimension lumber (width < 5") and heavy timber (width >= 5") are in the National Design Specification (NDS) for Wood Construction supplement: Design Values for Wood Construction. It is published by the American Wood Council of the AF&PA. http://www.awc.org/ Click on Design Standards.



[This message has been edited by Dick Schmidt (edited 02-28-2002).]

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