Tek-Tips is the largest IT community on the Internet today!

Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!

Register Log in
  • Congratulations MintJulep on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

How to justify timber grade 50 years ago

Status
Not open for further replies.
jason76

jason76

Military
Joined
Jun 16, 2009
Messages
1
Location
US
This time, I tried to attach a fireplace hood (400 lbs) to the existing wood joist. Using DF #2, I noticed the wood joist could not even hold its own existing loads. But the contractor argued that nobody use DF #2 50 years ago and the joist without any knots should be classified as DF #1 and better.

My question are how to justify the lumber grade 50 years ago and what kind of equivalent values we can use for today's calculations. I like to hear your thoughts.
 
Sort by date Sort by votes
Grading rules have changed a bit over the years, but your contractor might be correct. Further, it is possible you have a full size rather than nominal size joist (2x12 was actually 2"x12").

Find the prevailing grading agency for your area and see if you can get some historical data. The National Forest Products Association might be of some assistance.

The joist is obviously performing if you don't notice excessive deflection or creep, making it stronger than your calculation imply.
 
Upvote 0 Downvote
If the joist still has sawmarks on it, it may be full size. I don't know Ron's age, but 50 years ago, in Canada, a 2x12 was 1-5/8x11-5/8 and the lumber was seasoned (shrinkage was minimal). Typical Doug Fir was either #1 or Select and the flexural strength for #1 was 1500f and shear was 120 psi, if memory serves. These values were based on service loasds, not factored loads.
 
Upvote 0 Downvote
dik...I'm a little older than the project! In the US at that time, we had nominal sizing as you've noted for Canada; however, there were still many locally produced lumber items that were rough cut and sized.
 
Upvote 0 Downvote
There have been many posts on this subject, I suggest you google it at the top of the page.
 
Upvote 0 Downvote
Status
Not open for further replies.

Similar threads

J
  • Locked
  • Question Question
Retaining wall replacement (TIMBER SHEETPILLING)
Replies
5
Views
4K
phamENG
phamENG
fchris82
  • Locked
  • Question Question
Timber floor joists reinforcement
Replies
2
Views
2K
fchris82
fchris82
MAEngr
  • Question Question
New to existing CMU wall detail
Replies
0
Views
129
MAEngr
MAEngr
SHEAR_FORCE
  • Question Question
Sistering to Undersized TJI Floor Joists
Replies
6
Views
8K
SHEAR_FORCE
SHEAR_FORCE
Field Engineer
  • Locked
  • Question Question
How to survey a building
Replies
6
Views
593
Field Engineer
Field Engineer

Part and Inventory Search

Sponsor

Back
Top