A Timber Frame Scarf Joint
A Timber Frame Scarf Joint
When the Pilgrims and Spanish first landed in the "New World" there were vast tracks of virgin timber that had every size tree needed to build any kind of structure that was needed. In some of the original buildings still standing in New England one can find beams over sixty feet long with no breaks the entire length of them. The first European settlers here had the pick of the best timber for their projects, back in Europe at the time most of the forests had been very seriously depleted for building and for heating.
Today it is not so easy to find timbers that large that are structurally sound. You might be able to find some in the Pacific Northwest but throughout most of the country they cannot be found in any great quantity. So that leaves us with having to find ways to make short timbers long enough to make the wide spans that are found within timber frame designs.
The solution is the scarf joint. There are many variations of scarf joints to be found and each of them has a function that they excel at over other scarfs for whatever application you are using them for. When trying to determine which joint is best for your situation you need to understand the loads and forces that will be working against the joint. For the purpose of this Comment/How-to I am going to show you a stop-splayed and undersquinted scarf joint that will be a wedged joint.
The videos in this one are quite involved and are heavy on explanation. Hope you enjoy.
Laying Out the Joint Part 1
You have your timber cut and now it's time to start laying this thing out. So where do you start?
You start with a walk around of the timber you plan to use. You are looking for the best end of the timber to lay out your scarf but you are also picturing the rest of the joinery and what kind of issues that you may have to make allowances for or work around.
Once you have determined the best placement for the joinery it is time to find your reference face and your adjacent face. The rule for determining your reference face is that for any horizontal beam in the frame, the reference face should be pointing up. In the case of my tie beams I will be laying flooring over top of them and they need to meet on the same plane so that your flooring will be properly laid down the road.
Next you want to find the adjacent face to the reference face that is the most square to the reference face. The corner of the beam where these two sides meet will become the arris. This will be the most important reference point when it comes to laying out the timber.
Once you have all of those determinations made it is time to start laying out the scarf joint. In the above video the reference face, adjacent face and the arris will be made clear and explained in depth.
Finalizing the Layout
Once you've laid out the adjacent face to the arris off of the reference face you need to layout the adjacent face to the reference face opposite the arris. What a mouthful, hopefully after the first video the faces are clear to you.
As stated in the video above you should not have much need of a tape measure for this part of the layout. Your framing square should just about take care of the whole shooting match. Remember to square everything off of the reference face for this layout.
Using the reference face for all measurements and layouts is what you need to do to make up for any imperfections in the timber itself. You are trying to find the inner square of the timber so to speak. Once this is all done you are ready to start cutting the joint.
Cutting the Scarf Joint
Now we cut the joint. Remember to check your saws for squareness, make sure that you chisels are sharp and have at it. With these beams there is a lot of material that I had to remove to cut the joint, that's why the chainsaw was broken out. You will notice that I stayed off of the line while cutting with the chainsaw. A chainsaw isn't exactly a finesse tool to cutting joinery and it is not my common practice.
Take your time, it does not matter how long it takes to cut the joint and you can expect your first couple of times cutting these that it will take quite some time to make the cuts. Check for squareness often, you cannot do this too much. Hopefully you folks can find some useful information in these videos and if you have any questions or thoughts please leave a comment in the video comments and I will do my best to answer them promptly.
If you would like to learn more about timber framing and would like to see more tutorials then feel free to follow my YouTube channel as well as my Comment/How-tos. I will be writing an Comment/How-to for just about every video I put up on my projects.
Thank you for watching and reading,
Jim from TheTradesmanChannel 2017
Acknowledgments, Credits, and Bibliography