Another question - Weight of barn beams?

Schramm · February 17, 2013, 01:02:05 AM

I am doing some calculating on the weight of a barn beam in these 3 species which I am picking up and having delivered this week and upcoming weekend. I have done some calculations and read that pine logs weigh about 30lbs per cubic foot but have no idea what that means when it comes to a barn beam. First it is mainly dry to about 12-15% MC and most of what I am getting are 1. Heart Pine 2. Douglas Fir 3. White Oak, beams are no less then 110 years old and no more then 12' in length. Is there a real weight on these beams? I am hoping to be cutting sometime next week or the very next week. I have to start making some flooring for a rehab.

Thanks for any info you can help me with. I am not looking for exacts, just a good way to give a good guess.

Rob

mesquite buckeye · February 17, 2013, 01:19:49 AM

All of these will be heavier than 30lb/cu ft.

To get the answer you have to calculate the volume of the beam in cubic feet, which means width X thickness X length in feet, then multiply by the lbs/cu ft for the species (which is actually variable).

or inches width X inches thickness X inches length divided by 1728 to get the cubic feet, then multiply as before.

hard pines run around 35lbs/foot

doug fir 31

oaks 40-48

Schramm · February 17, 2013, 10:54:36 AM

Got ya and thank you! Very simple way to figure it out. I found a guy with a mother load of various species of barn beams and I am leaving to go and check them out now. He has them in 10' lengths so they run about 250 lbs per beam.

Thanks
Rob

mesquite buckeye · February 17, 2013, 11:02:50 AM

No problemo ;D

Schramm · February 17, 2013, 11:09:17 AM

Another question: I have seen the beams in pictures and all the ones that I am getting are 10" square and they are very straight, so if I milled them down to 9.25" x 9.25" and then cut them down to 9" x 1" pieces I should get 9 out of each beam. The beams are 10' long so my question is this: "Does the Doyle log rule apply to barn beams?" The reason I ask is at the figures given in that rule a 9" log will only yield 16 board feet at a 10' log.

From my figures I will end out with a 9" x 1" piece, now instead of the log rule using sq footage figures (9" x 120" = 1080 si x 9 pieces = 9720 si /144 = 67.5 sf per beam). Now I know that in milling it goes by board foot but there really is no difference in size as a square foot is 12"x12" and a board foot is 12"x12"x1" the results are the same. Am I right or am I missing something as according to the Doyle rule I would end out with 16 sf.

Little confusing for a first timer so an explanation would help.
Thanks
Rob

mesquite buckeye · February 17, 2013, 11:25:06 AM

Doyle Rule is for converting roundwood to 1" boards usually with a 1/4" kerf, so typically underscales what you get from logs, which has nothing to do with what you are doing.

Those really straight beams aren't. You will find out how unstraight when you mill them up. If they deviate just an inch or twist a little, you will lose more.

Just saying, calculating how much you need to produce a certain amount of lumber only goes so far. It comes down to what comes off the mill.

Let's say you can come up with a square straight cant that is 9 X 9, then you still have to saw it up into boards, you lose the kerf of every cut, which depends on your saw. Woodmizers lose about 1/8" per cut. So with that 9 X 9, you could end up with 8 one inch boards. If you can live with something thinner, you can get more slices.......

If the blade gets dull, doesn't like the old hard wood and wanders, you have more loss....

Hope this helps.

mesquite buckeye · February 17, 2013, 11:26:44 AM

To figure board feet, measure inches wide by thickness by length in inches divided by 144......

redbeard · February 17, 2013, 05:54:39 PM

Schramm some other things to consider when buying and sawing reclaimed beams especially milling flooring. Your going to have to account for a lot of loss due to knots , checking and metal wounds if your counting on getting full value from every beam its not going to happen. Centers and juvenile wood will make up a lot of the beams in a demo sale. There will be a majority of tight grain old growth but you will also get the beams that won't make the grade you need to get top dollar.

What I look for are the ones free of center on both ends. When you can find them like the close up pic they will yield full bf of flooring lumber. Good $5-$7 bf Doug for flooring has to be clear and qrt sawn with end grain 60 to 90° hope this helps a bit.