Making a Beam

[WV TreeTopper]

Hello everyone. I am currently constructing a pole building and am looking for some advice on tying boards together to make a beam. I can mill up to 17' and need to span a 20' gap maybe 30' if you guys think I could do it. I was planning on using Norway spruce or maybe poplar . Also was wondering on the best way to tie my runner boards to the poles where they would but together. I don't have a large surface to tie into because I didn't kill my posts down. Was thinking about putting a a small 2x2 or 2x4 board on the post before I tore my main runners on. Any advice would be much appreciated. 

[WV Sawmiller]

   Have you checked out this tip from the Extras on the FF Home page? I have not done it yet but it describes how to cut a longer log than your mill.

https://forestryforum.com/board/index.php?action=tips

    Sorry you are on the wrong end of the state. I can saw  21' on mine and I'd be glad to help get that 20' beam for you. I even have a patch of Norway Spruce we could probably get one here but still a long beam and a long way to go. Good luck. 

[WV TreeTopper]

  Have you checked out this tip from the Extras on the FF Home page? I have not done it yet but it describes how to cut a longer log than your mill.

https://forestryforum.com/board/index.php?action=tips

   Sorry you are on the wrong end of the state. I can saw  21' on mine and I'd be glad to help get that 20' beam for you. I even have a patch of Norway Spruce we could probably get one here but still a long beam and a long way to go. Good luck.

Haha thanks for your reply! Yea I wish you were closer not only for the beam but to come pick your brain about all this stuff haha. Good to know different sawyers in the state though! 👍🏼

[SawyerTed]

I've built beams to span an 18' garage door opening by making a sandwich of 2x10S and plywood.  I normally use a construction adhesive and plenty of fasteners.  Of course all joints are staggered at least 4' apart. 

My house has two load bearing built up beams with 2x10s and a steel plate bolted in the middle of the sandwich.  

[Don P]

In this situation it might be better to look into LVL's.
One thing on forum etiquette, make just one post on a question, it gets all messed up when the same question gets going on multiple boards.

Usually on a round post it works better to make flat spots to attach members to. I'll usually do that by lightly brushing with the chainsaw till I get down to the flat spot. Figuring out the top and bottom flats and installing those members plumb in relation to one another and then stringing or plumb stick and marking the location and depth of the middle flats. Then go to the far end of the building and repeat, then string from end to end and lay out the intermediate posts.

[WV Sawmiller]

   We live in a log home made from a kit of some type and have a big laminated beam in the great room about 6" X 24" X 36' long. It appears to have been made by using dressed 2X6's of assorted lengths with the various internal ends staggered for strength, glued and clamped. I could see where such a beam could also be made using long decorative (Black wrought iron?) bolts, nuts and flat washers holding the pieces together for strength and decoration.

[Don P]

I'll take us off on a tangent for a minute,

Trying to make a site built glulam beam is generally not a good idea. The tendency of the individual layers to slip and shear is pretty substantial. They are using rigid glues and good material surfacing under controlled conditions to produce that joint. That is not rough sawn and construction adhesive. To visualize what is going on with shear in bending take a phone book and bend it, watching the pages slip past one another to accommodate the bending. If you fail to get even one layer well attached that slipping will occur. That is why we can on site make built up beams by nailing together lumber on edge but you never see a builder make a beam by nailing together horizontal plies flatways.

I remembered some pics on my gallery showing this. Notice something here as well, the point of maximum bending moment, the center of the beam, is the point of zero shear. The point of greatest shear, the ends, is the point of zero bending moment. The stresses in a simple beam are the inverse of one another. There is much more to it than just this, where would one safely scatter joints, where would one place the best lumber, and how much is the right glue for this going to cost.



 

 

 

    

Carry on

[Bandmill Bandit]

I once did 2  "small" beams this way. One each for bow and stern of my cedar strip canoe. 

They have held "up" for 32 years. BUT I would not attempt anything larger my  self. They are 1.5 in wide tapered to 3/4" and 42 inches long bent to about 115° curve. 

I used hockey stick handles busted sticks ripped to 1/8" strips, steamed for about an hour and then glued/clamped (clamps every 2 inches) to a form with the same glue that was used in a local arch rib manufacturing company and it was not cheap. That was back in the day when hockey sticks were made of high grade Ash. 

[WV Sawmiller]

Don,

   What about if you put a long through bolt every few feet to prevent slippage?

[kelLOGg]

Do the beams have to be sawn? Can you use suitably sized logs and lightly brush them with a chainsaw ala DonP to make the appropriate flat? I have done this on 2 sheds using utility poles. Two bolts thru the beam attach to a cross bolt in the post to snug them together. First shed built like this was 20+ years ago and it hasn't moved. Good luck whatever you decide.

[1938farmall]

amen on leaving the log as-is.  this subject comes up all the time.  i did the same 15 years ago for a 24' span with a 18"/15" poplar log.  looks as good as day 1 -  much less labor (and thinking)

[SawyerTed]

On site built up beams are a very common method of spanning between support posts.  Most building codes address on site constructed beams, joint placement and fastener placement.  With the availability of LVL now, built up beams are likely less common than they used to be. 

The majority of built up beams I've constructed in the last nearly 40 years have been inspected and all have passed without a problem. Twenty feet is the greatest span I would try without a steel plate sandwiched between members.  For a 20' span a built beam with a plywood center is not poor construction method. 

The photo below shows a 2x8 with a 10" plate through bolted with a 2x8 on the other side.  This beam spans 20' under my deck. The steel plate (instead of plywood) was required due to weather exposure under the deck. It's been in place 32 years 


 

[Don P]

Don,

  What about if you put a long through bolt every few feet to prevent slippage?

Still too much slip. Add split rings, shear plates, something along those lines and it'll get you there. It won't time or cost out. This is simply not the way to build a beam in the field.


For built up, vertical plies like Ted shows that shear problem goes away. Well you still check the wood strength in shear but unless heavily loaded, usually short and heavily loaded the shear strength of the wood is adequate, you'll see the beam calcs doing that as the last check. The nails or bolts are simply holding the plies in a built up beam in relation to one another (if top loaded!) rather than being heavily structural like the shear enhancers we were talking about above, life gets much easier. Joint placement is by code over a post in the US, full span length members, no breaks in the span.

Generally people make sure to note that they added plywood to a built up beam. The plywood adds dimension if you need to match a post or wall thickness, it isn't adding strength. Construction adhesive can add stiffness, it also does not add strength.

The built up beam (vertical plies rather than horizontal of a glulam) with a steel plate is a flitch plate beam. The steel carries the load, the wood restrains the steel from buckling. They are not particularly efficient as far as steel required for load carried compared to say an I beam but we used them regularly in residential up till the 90's or so when LVL's pretty much filled that need. I don't really miss hefting them into place or worrying about one of us slipping on the ladder with that guillotine in hand. I have a table and equations here somewhere if needed. Sounds like Ted probably has that same old NAHB table in his toolbox.

The log beam is a good idea. A log of the same species and grade is substantially stronger than a sawn beam, we haven't damaged a good bit of the nice continuous, long, fiber straps that are present in the log. We don't saw logs to make the wood stronger, we saw into convenient to use shapes at the expense of strength. The skimmed top beam is the SRTB, right hand side in this calc;
https://forestryforum.com/members/donp/logbeamcalc.htm

That was probably all TMI. I'm about dry, off to the salt mines again :D

[PA_Walnut]

I am not an engineer, nor a safety officers. So, take it for what it's worth.
I needed to span 21' for my kiln doors. (insisted on being able to front load, not side load...been there, done that).

Laminated four 2x12's together for a "glue lam" 8x12, staggering the joints, with construction adhesive and Timberlock screws. So far, a year later, it's sagged <1/8" total. It's no big deal to me since I designed the doors/seals with a bit of variance in mind. 

Just cut some more oak for another span I have to do, which is even longer. Trying it to see what happens. I guess when you have a mill, all roads lead to sawing more wood!  :D ;D