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Author Topic: How to Join 2 Beams?  (Read 7172 times)

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Offline rost495

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How to Join 2 Beams?
« on: May 04, 2010, 04:04:18 pm »
Searched and did not see this addressed specifically and it may be a non issue, and I'm not familiar with joint terms either much....

What I'm trying to do is salvage some old hand hewn cedar beams from a cotton gin that fell down on our place. 

I need 14 feet 6 inches to span a room and have only basically 12 footers that are solid.

This is not structural, I simply want to use it as decorative.  I have a seem on my ceiling(roofing tin) that I can cover up this way also.  I"ll have a vertical beam on each end to support the ends, and I'll use a way to support the beam ends, like a hole in the beam and shave a wedge to the top of the vertical support to slip into that hole.

I will also more or less hollow the beams some with a chainsaw to reduce weight. 

I intend to use half inch smooth rod beat flat on an anvil and create hangers that can straddle the beam and then be supported by 2 ceiling joists.  Space those basically at  3.5 feet. 

So what's the best way to cut the ends off two of the beams, and join them? I think I have a big dovetail on one end I could salvage, and just do the female of that and peg it through the middle?

Thanks and thanks for your patience.

Jeff

Offline Brad_bb

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Re: How to Join 2 Beams?
« Reply #1 on: May 04, 2010, 06:24:07 pm »
Welcome to the forums!  

It depends on what you want to end up with.  I'm guessing you're not yet familiar with timberframe joinery techniques.  What you want to do is "scarf" them together, or rather create a scarf joint.  There is a simple lap joint, to a more complex keyed, undersquinted, splayed.... scarf.  Others may jump in with pics as I know some here have the pics in their photo albums.  You didn't say what dimension beams you are working with.  I suspect you will want the simplest scarf?  For that I assume you'll use steel hardware to join them?  For the most part in timber framing, traditionally you don't use steel hardware, but rather wooden wedges on a scarf.

14.5 feet isn't a too big a span.  You should be able to support it on each end with no problems and no need for a "hanger".  Typically though, a scarf is supported by a post or other member at the scarf, but being supported so close to the end and being decorative should be sufficient.

I don't know why you'd need to hollow the beam out.  Supported on the ends it should be fine whole.

I don't understand why you want hangers on each rafter if it's supported on each end?
Anything someone can design, I can sure figure out how to fix!
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Offline PlicketyCat

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Re: How to Join 2 Beams?
« Reply #2 on: May 04, 2010, 09:50:40 pm »
If you search for "Scarf Joint" on Wikipedia, there is an external link to "3D diagrams showing Scarf Joints" at the bottom of the page. The site it links to has the best diagrams of these joints that I've been able to find outside of older joinery books.

http://www.craftsmanspace.com/knowledge/scarf-woodworking-joints.html
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Offline Meadows Miller

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Re: How to Join 2 Beams?
« Reply #3 on: May 05, 2010, 05:56:56 am »
Gday

Welcome to the forum Jeff  ;) ;D 8) for a non structural beam ive cut the center out of full length ones in the past on a Lucas but any adjustable table saw will do it too  and leave a u shaped outer skin then just screwd it to a beam that will carry the weight  and put it over it like a cover it will work just as well for your two sections Mate  ;)

Regards Chris
4TH Generation Timbergetter

Offline routestep

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Re: How to Join 2 Beams?
« Reply #4 on: May 05, 2010, 07:21:31 am »
You could cut a slot in the two abutting ends and peg in a spline possible made out of plywood or a solid piece of wood.

I know the price is right by using what's onhand, but it might be easiest to just buy a 16 footer if you only need one and cut to length. Your first splice could look a little rough.

Offline Jim_Rogers

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Re: How to Join 2 Beams?
« Reply #5 on: May 05, 2010, 07:24:30 am »
Problems with hollow beams: first they may just fall apart. The problem with hollowing out a beam is that it may just fall apart. What I mean by that is that the beam that is left which is in the shape of a U will dry out completely very quickly if not dry to the core already.

This dry beam will crack, again if not cracked already. And these cracks can run right down each side from end to end, and make the hollowed out beam very weak.

When I hollowed out a new beam for a carpenter, who needed it for hiding a LVL we created counter sinked holes in the bottom surface to use to lag the hollowed out beam to the LVL. And then pegged the counter sunk hole and cut the peg off flush with the bottom surface to make it look like it was pegged in place.

As we were hollowing out this fresh sawn white pine beam, it started to dry and the two sides of the U started to spread further apart, to the point where it was almost a V. So to prevent this from happening we screwed down some cleats across the top of the U to hold the two sides at the correct distance apart, until the carpenter installed it around the LVL and he then screwed through the sides as well as the bottom to hold them from spreading apart while in place.
I never saw it in place but they never came back to complain about how it came out.

Now adding to all this you want to have a scarf joint in this beam some where.

I would not consider this idea to "hollow out" the finished beam the best solution.

If you have two posts that can hold up this decorative beam then you don't need to worry about it being heavy.

You'll need to create the proper scarf joint that will hold itself up and straight over the 14' span. Most any one will do as you can use lag bolts or long screws from the top down to hold the joint together and they won't show. Or you can counter sink some holes for the lags and put in false pegs to cover them.

Good luck with your project and if you need more help post more questions.
Whatever you do, have fun doing it!
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Offline Brad_bb

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Re: How to Join 2 Beams?
« Reply #6 on: May 05, 2010, 09:04:37 am »
Not sure if you know how to properly layout the simple lap square, how to use the saw properly, or a framing chisel.  There is a technique to using a hand saw to get a nice, square cut.  You can leave the blades of the lap slightly long and par with your chisel to sneak up on the final fit to make it a nice tight fit. 

First, proper technique to get a square cut is to pick a reference edge, and then a primary and secondary face from that edge.  The reference edge should be the edge where the faces are most square.  Draw your lines from the primary face across the board/timber, and drop the two short vertical lines.  Finally start scoring cuts with the saw along your lines.  These will act as guides for your saw.  Now saw from top corner until your saw reaches the bottom of one of your dropped vertical lines and the opposite corner (a triangle).  Then turn around and do the other corner to corner.  Then you can use the kerf to finish the cut and you have a totally square cut.  Laying out your lines on hand hewn timber is a bit trickier.  You would need to snap chalk lines on your timber to use as references for your square.  Since you don't have a straight edge, you need to establish them with chalk lines, but that's a lot to understand right off, so I won't go into it just yet.
Anything someone can design, I can sure figure out how to fix!
If I say it\\\\\\\'s going to take so long, multiply that by at least 3!