Structural strength Ratings?

[huskymac]

Does any one know of a Structural strength rating graph or chart . I'm kicking cabin ideas around. and I was wondering about using trees on site. Hickory, Oak, Ash, Dogwood, Elm, Locust, Maple. Quite mix really, but I don't want to strip the land of any one species. What I'm after is comparing load carrying ability's. For example a 6"'x 6" 8 foot Oak beam can carry X amount of weight. How big would a Elm or Poplar beam need to be to carry the same load?

Any Help?

 

[Metals406]

Load rating aren't just based on species... It's based on grade too. You can call your local lumber yard, and they should have load ratings on hand per species and grade... But then comes the tricky part... You have to be able to accurately calculate the loads you'll be putting on said beam... As well as judge your lumber accurately, to grade it to the acceptable level.

Then you have the issue of mixing species... They'll have different grain structure, hardness, drying time, compressive capability, etc. I've never seen a log home built with multiple species... Just one. Two of the most common are spruce, and lodgepole pine. Granted, I'm sure they use hardwoods in the Eastern U.S.

Nothing wrong with some good ole fashioned farmer-sense... Build it where it looks strong, and it probably will be. You may even be able to get some tips from a local log builder in your area.

EDIT: I just read that you're a cabinetmaker, so you know your way around wood. Go with the lumber yard thing... They should have those charts.

 

[Mike Van]

If this cabin is something you're going to live in, you might want to run this by your building inspector. Some require 'graded' lumber only, or an arcitect or engineer's sign off on your work before you can get a permit or c.o.

 

[gink595]

There are plenty of old post and beam style bank barns here in the Mid-west that are made of mixed hardwoods, if in doubt over engineer it, thats what they did 100-150 years ago, alot of them are still standing. Same with most of the old farm houses, all native lumber.

 

[Leroy in Kansas]

Huskymac,
I believe some of the information you are seeking can be found in a book by Jack A Sobon, title, Build a Classic Timber-Framed House. In the back of the book there is "An introduction to Structural Design". Although this will not make a structural design engineer of you it may help with some of the questions. Leroy

 

[scottr]

Huskymac, I'll bet that the information is in the Wood Handbook. http://www.fpl.fs.fed.us/

 

[woodshop]

http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr113/fplgtr113.htm

This takes you right to the handbook, you have to dig a little to get the info you need, I'd grab a cuppa joe and dig into chapters 3 and 4. If you're not very familiar with some of the terms, you might want to read some of the earlier chapters that explain some of the basics.

This is a great resource, but sometimes you just have to dig a little and work for what you want to find.

 

[huskymac]

Thanks guys!

That is some great Info! Tons of useful stuff!

Ive been playing and working with wood for 40 years now. As Bobl said in his BIL mill thread I know just enough to know I have a lot to learn!

My cabin idea is to build a small post and beam frame and then use SIP's (structural engineered panels) to fill in the walls and roof. I was thinking of using Hickory for the 8x8 beams. My idea of mixing species would be the 4x4,s that are buried in the sips and also for rafters sill plates etc... Drying times and shrink rates could be of concern but this project will be spread over 5 to 6 years so I think I should have adequate drying times before I actually start building.

I spent the day cutting and hauling firewood yesterday. While I was there I got a couple of fair sized Ash trees lined up for milling. The weather took a turn for the worst today so it looks like it will be awhile till I can get out and try the new mill.

 

[gink595]

After reading this thread this morning I found my old Timber Frame book and I was reading about the different species this book listed as good candidates for a timber frame. It said for:
"Hickory this is the strongest and heaviest of our native woods. But hickory, like beech has a high shrinkage rate and should beworked quickly to reduce splitting. Care in seasoning is especially important with hickory timbers.

Ash: Strong and fairly heavy, ash has a medium rate of shrinkage. It does not work as easily as a wood like oak."

It sounded like white oak was one of the most popular for the old timber frame structures, it said it resisted decay very well. That was surprising to me.

 

[wdchuck]

After reading this thread this morning I found my old Timber Frame book and I was reading about the different species this book listed as good candidates for a timber frame. It said for:
"Hickory this is the strongest and heaviest of our native woods. But hickory, like beech has a high shrinkage rate and should beworked quickly to reduce splitting. Care in seasoning is especially important with hickory timbers.

Ash: Strong and fairly heavy, ash has a medium rate of shrinkage. It does not work as easily as a wood like oak."

It sounded like white oak was one of the most popular for the old timber frame structures, it said it resisted decay very well. That was surprising to me.

White oak was a mainstay in shingles in the New England homes for centuries. Then there are the barrels and ships made from it. Trailer decks made from white oak take a beating and weather great, horse paddocks, fences, corrals...

Black locust would make fantastic ground contact wood, just need to keep the tooling sharp as can be.

 

[Metals406]

That is some great Info! Tons of useful stuff!

Ive been playing and working with wood for 40 years now. As Bobl said in his BIL mill thread I know just enough to know I have a lot to learn!

My cabin idea is to build a small post and beam frame and then use SIP's (structural engineered panels) to fill in the walls and roof. I was thinking of using Hickory for the 8x8 beams. My idea of mixing species would be the 4x4,s that are buried in the sips and also for rafters sill plates etc... Drying times and shrink rates could be of concern but this project will be spread over 5 to 6 years so I think I should have adequate drying times before I actually start building.

I spent the day cutting and hauling firewood yesterday. While I was there I got a couple of fair sized Ash trees lined up for milling. The weather took a turn for the worst today so it looks like it will be awhile till I can get out and try the new mill.

Okay, post and beam. When I hear the words 'log cabin', my brain defaults to logs stacked on top of each other... So the species mixing thing would be irrelevant in this case.

I think you'll like using SIP's... They work good.

 

[redoak]

husky,

I'm in the process of building a post and beam barn. All the timbers are white pine, none larger than 8"x8", no unsupported span greater than 10'. I ran the numbers and with those timbers I could have gone as far as 16' spans. The trees you mentioned are considerably stronger. I say as a rule of thumb, using 8"x8" timbers, you can span up to 16' without worry. Anything longer than that you'll want to run the numbers.

I really like Sobon's book, but if you want to double check the engineering of your frame design pick up a copy of A Timber Framer's Workshop by Steve Chappell. He gives you the all the details right down to checking the relish on your tennons and shear on the pegs.

They say with hardwoods to let them season before cutting the joinery. I had a 250 year old colonial and the joints were still tight... they did not frame that building green. All timbers were red oak, some with the bark still on which was a real nice thing to contemplate.

-redoak