I was looking at these 4″ x 8″ x 8′ cedar beams the other day for a project in my “dude room”. I believe I can pick them up for $7-8 lf
I want them for posts to support a loft.
I was amazed at how light they were!
So I check my book on wood species and found that (other than N. White cedar) the compression PSI was relatively the same for it as oak, hickory, pine (strangely most species of fir were ALOT higher, but I digress). I was just amazed!!! Especially with how light it was. So I decided this is a fine choice.
Do you concur?
However I did want to consider using 2 cedar 4 x beams to span 11′ While not quite as high as the species mentioned above, the PSI for horizontal forces seemes adequate. However I can’t locate a span table for that wood.
Any ideas???
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WWPD
Edited 3/15/2006 12:59 pm ET by Sailfish
Replies
Do you want to meet code or just build the thing.
If you want to meet code, see if you can get span tables from the manufacturer of the wood that are AF&PA approved. If not, time to get the engineer.
If you don't care about code and you can't get span tables, and you know how to do some basic wood frame engineering, see if you can get engineering values (fiber strengths: Fb, Ft, Fv, Fc perp., Fc, and modulous of elasticity, e). From those numbers, you can calculate deflection and failure but if you've never done it before and it's not something that interests you to learn, again, get the engineer. (If you do "home brew" engineering, do NOT forget safety factors -- at least three times design load).
For "seat of the pants" a 4x8 made out of solid cardboard would "probably" hold as one of the columns for a small loft (a joke, of course), so solid cedar of good grade "should" do the job. But then, how many of these columns will support the loft; plus there's a lot more to it than just compressive strength (likely Fc -- compressive strength parallel to grain is what you were looking at). You also need to factor in the modulous of elasticity, e, and the slenderness factor which relate to the tendency of a column to bend under high stress. Put enough weight on a slender column and it will fail regardless of its compressive strength. Just seat of the pants might tell you that a set of 4x8 post have got to hold up a small loft. On the other hand, if one of your columns fails and God forbid one of your children are under it when it does --- you get the picture. Get the engineer.
For a horizontal beam, I can't give you a seat of the pants. Depends a lot on your design and the characteristics of the wood. For the most part, fiber bending strength and modulous of elasticity factor in. But your design might also put the wood under high tension, or who knows. There's too much that goes into to it to guess that a cedar 4x8 would "probably" hold.
Anyway, all that Fb, Fc, e, jazz (you probably want to tell me Fu) is so that you'll see there's a lot more to it than compressive strength out of a book. If you want the thing to hold, get approved tables or an engineer.
"A job well done is its own reward. Now would you prefer to make the final payment by cash, check or Master Card?"
thinking cedar post and "span" real differentas for references / resources people are always listing span table type sites and there is the Western Red Cedar Bureau ( seems to me they changed their name to match the times of late ) that you could google and they have people that answer the phone if span properties are not addressed on their sitejust off the cuff I'd take away 30% or so span strength quotient to be safe but what you going to put in this "dude room" loft anyway?Our Indian bretheren consider this wood a gift of the Gods
so many wonderful uses but no match for dougfir, oak or hickory in the span departmentrough cut cedar & brackets / braces go well together and cut your span
I don't know but regardless go get those beams before they get away.
'Nemo me impune lacesset'
No one will provoke me with impunity
Wish I could think in practical terms more often. I have to hang around here more.
Best advice I've ever seen. ;-)
"A job well done is its own reward. Now would you prefer to make the final payment by cash, check or Master Card?"
Jeez Rez, I was thinking of you the minute I read the first post. Wanna go in halvies on a warehouse?
edited for poor spellingBirth, school, work, death.....................http://grantlogan.net/
Edited 3/15/2006 6:16 pm ET by seeyou
All ya need's a shed to kept 'em dry and there's no monthly with interest:o)
I mean 7-8 bucks for an 8ft 4x8? H*ll! Buy'em all and build one out of cedar! Roar!
edited because I wanted to.
be seeyou, youseedar big wooden sticks o'er dere?
'Nemo me impune lacesset'No one will provoke me with impunity
Edited 3/15/2006 7:44 pm ET by razzman
It's not 7 to 8 bucks per post.It's 7 to 8 bucks per lineal foot.That means an 8 foot post will cost 56 to 64 dollars. Then tax....
I've got you outnumbered, one to one. Come out and meet your doom. ~Yosemite Sam
In that case go cut yer own .
be have chainsaw will travel
'Nemo me impune lacesset'No one will provoke me with impunity
Now you have the plan !!
I've got you outnumbered, one to one. Come out and meet your doom. ~Yosemite Sam
You guys up north have is so good.
There are no tree around here.
No mills around here, limited choices of wood.
I gotta pay up the yang for wood.
It would be nice to live up there.
Well except for the cold.
And the snow.
And hayfever.
Lack of Warm water.
12 week summers.
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WWPD
Yep, cold ain't cool no matter what the ski bozos say:o)
be rather fried
'Nemo me impune lacesset'No one will provoke me with impunity
LOL! in terms of price, they are worth it just to stack up and look at, ain't they?
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
And they smell pretty, too.Birth, school, work, death.....................
http://grantlogan.net/
Here is a Mech. prop. of wood pdf.
They are fine for posts, but cedar beams scares me, depending on span and load.
When you talk compression, they are similar in length, but laid horizontally, you need a different set of words. Compression really does show then
Welcome to the
Taunton University of Knowledge FHB Campus at Breaktime.
where ...
Excellence is its own reward!