1907 Lumber Values. 1

[RARWOOD]

The Carnegie Pocket Companion-1923 which SlideRuleEra has talked about before, gives design values for wood.

Those design values are quiet high, so I am unsure of how to apply them for use in evaluating wood from a building built in early 1900. Does anyone have any suggestions?

I am trying to get an estimate of what design values may have been use in order to determine the orginal loads that a building was designed for.

 

[dougantholz]

- rule of thumb is wood that old is select structural or dense select structural. You can get the species through your local APA or agriculture extension office.

 

[SlideRuleEra]

RARMBJ - The note at the top of the table of "Working Unit Stresses for Structural Timber" (page 289 of CPC-1923) gives this guidance:

For building and similar structures, in which the timber is protected from the weather and practically free from impact, the unit stresses may be increased 50 per cent.

I agree that this would make the allowable working stresses quite high by today's standards. Engineer's in the early 20th century do not appear to have had knowledge of "load duration". I have never seen that issue even discussed in publications from that time. Also they were willing to accept a much smaller safety factor then (typically 6 to 1, and if the 50% increase is taken into account it becomes only 4 to 1). This probably had to do with the fact that almost all timber used at that time was high quality, not the wider variability seen today.

In summary, IMHO, for a building that meets the above requirement, I would apply the 50% increase. This would be to determine what the ORIGINAL design loads were. But... I certainly would not say that the structure is safe (by today's standards) at those loads.

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