Timber Frame Joinery Details

We are compiling this library of timber frame connections for you whether you are a carpenter looking to expand your skill set or a visitor looking into how we build here at Joint and Peg.  This is a free resource that we have built from our experience in designing and building timber frame structures.  To enjoy the ability to download all of these details in pdf format, you will need to purchase one of our plans and include the library add-on. Our joint designs are some of our own, and others are handed down from generations of master to apprentice.  We update our library frequently as we provide more stock timber frame plans and frame packages.

We provide both examples of using rough sawn timbers that vary in cross sectional dimensions and examples of joinery using s4s timbers that are consistent in cross sectional sizing.

Please note that these details are for reference purposes only.  They are only small details of the bigger picture which is not shown in these drawings. 

Classification of Rough Sawn and S4S Joints

Working rough sawn timber requires that you find and layout a regular (consistent) timber inside timber that varies in cross sectional sizing. The joint diagrams we have provided dimension’s datums are logical to that end. Insightful call out hints on how to accomplish the task of working with rough sawn timbers are also on each detail sheet to help you along the way.  You will see reference planes in purple that are the basis for all quality construction.  This is especially true for the square rule method of timber joinery.

Categories are by Timber Type (Rough sawn or S4S), then by the area of the frame that you would find or need the joint, and finally by the name of the joint. Please note that if Timber Type does not say Rough Sawn or S4S, then the detail could be suitable for both.

For example, we could have:

Brace Joinery

Rough Sawn – Braces – 4×6 Bareface Knee Brace

This joint is a bare face knee brace tenon and is typically used when you have rough sawn material.  The brace is oriented flush to the reference face of the post which makes cutting the housing much easier and more accurate.  We recommend finding the tallest brace stock you have and making all your mortises a corresponding length (usually longer) to accommodate that extra height.  Then you won’t have to plane back the tops of your braces. The length of mortise in the drawing is if the brace stock is exactly 6” high.

Rough Sawn – Braces – 2 Bareface 4×6 Knee Braces on Opposite Faces

This is a common situation in timber frame structures with knee braces.  You have (2) braces that are on opposite faces of a post and springing from the same level. In this situation you need to use a shorter brace tenon and make sure that there is a 1/2″ gap between the two tenon ends if using green timber.  This allows shrinkage of the post to occur without having the tenons collide. We typically adjust the peg layout a bit to allow for more relish beyond the peg to the end of the tenon.

Rough Sawn – Braces – 8×8 Post, 8×10 Beam, 4×6 Brace Triangle

These components and these instructions make up the crux of building timber frames with square rule joinery.  It shows the difference between laying out a brace from a reference face and how the knee braces are always the same length critical point to critical point regardless of the length of the tenon on each end.

Scarf Joints

Rough Sawn – Scarf Joint – 8×10 Beams with Keys

This scarf joint is placed over a knee brace.  You will either have to clip the knee brace tenon or cut out a relief in the table for the tenon. The centerline of the scarf is the reference to lay this out. Please lay out and cut the scarf joint and test fit and tune until there is a good fit.  Only at that point should you layout the remaining joinery on the timbers.  The top of the plate is the reference, any variation in top plate heights should be justified to the bottom.

Tie Beam and Girt Joinery

Rough Sawn – Tie Beam – 6×8 Tie to 8×8 Post, Square Housing

This tie joint illustrates a tie that has a width less than the post and how the two connect. As this is rough sawn material, you will want to reduce the non-reference faces so that your ties can all fit in the same size mortises in the posts.  Therefore, you reduce the bottom and inside of the tie as shown in this diagram. A 6X8 is on the small end of tie beam sizing.

Rough Sawn – Tie Beam – 6×8 Tie to 8×8 Post, Diminished Housing

This 6×8 tie joint illustrates a tie that has a width less than the post and how the two connect. As this is rough sawn material, you will want to reduce the non-reference faces so that your ties can all fit in the same size mortises in the posts.    What makes this diminished housing nice in square rule is that you can use the bottom of this member (if nothing is on top of it like floor joists) as the reference and thereby let any variation in the height run right out of the triangular housing.  That geometry does not change. Therefore, you only reduce the inside of the tie as shown in this diagram.  Again, a 6X8 is on the small end of tiebeam sizing. Typically tie beams are 8×10 and larger.  This detail is from a small, shed structure.

Rafters

Rough Sawn – Rafters – 4x Rafter, Simple Birdsmouth

This is the simplest way to connect a common rafter to a top plate in a timber frame structure.  There are other more complicated joints but when there can be a large number of these connections that typically require a structural screw anyway, we like this simple connection.  The important measurement is the H.A.P. (Height Above Plate).  This measurement will be given on your frame plans.  Even if your rafters change in height, if you use a common H.A.P., the tops of your rafters will plane out.

Posts

Rough Sawn – Posts – 8×8 Post Top to Top Plate

This 8×8 Post Top Tenon is going into a top plate that is the same width (8×10) and therefore only needs reducing in the axis of the mortise (parallel to the top plate). As the housing runs all the way across the bottom of the top plate any variation can just stick out on the inside of the post.  Anything unsightly, in the way of a lot of timber sticking out, means your Sawyer is not doing a good enough job!  Always remember to make the mortise deeper than the tenon so it doesn’t bottom out. Any posts on the corners should be referenced from the outside face.

Posts – Post Bottom Timberlinx A475 – CMU Pier

With an elevated pier to 8×8 post connection this will work well. Some may prefer to use a 1″ thick standoff instead of the 1/2″ thick one shown on this drawing. The post is connected to the pier with the use of a Timberlinx a475 that has a 7/8 threaded rod that is epoxy set into the grout filled and reinforced cmu pier. The rod could be cast just as easily in this situation before the grout is filled in the CMU stack. Regarding the Timberlinx a475: there are (2) drillings that are made. One plumb and the other level. See Timberlinx manufacturer specs for drilling diameters. We typically use a 1 1/8″ dia. level drilling and a 1 1/4″ dia. plumb drilling. The timberlinx anchor is a go to with heavy timber to foundation connections.

Posts – 8×8 Post Top to 6x Top Plate with Tie Beam

You can save a good bit of material using thinner top plates and ridge members. In this instance we have an 8×8 post with a 6×10 on top of the post.  The depth (9.5″) is more important from a structural standpoint.  Furthermore, a 6x typically stays straight and can look nice when atop a bigger post with the chamfered detail you see in this joint library entry. Please look for “Tie Beam Joints” when it comes time to connect the tiebeam in this diagram.  If you are not opposed to structural screws a few 9mm fully threaded structural fasteners will keep the tie beam in a majority of circumstances.