Many construction guides will state the use of mortise and tenon joints. However, not every guide will tell you what these are, where they may be used, or their advantages and disadvantages.
As award-winning specialists in oak and timber frame construction with over 30 years of experience, we have put together a full guide with all the information youâll ever need.
What Are Mortise and Tenon Joints?
The simplest way to explain a mortise and tenon joint is to imagine âtab A being inserted into slot Bâ. It is a basic compression joint comprised of two parts, the âmortiseâ, and the âtenonâ.
- Mortises are sockets, recesses, or holes cut into a material (usually timber) in order to connect it with the tenon (or âtongueâ).
Tenons or tongues are projections on the end of a piece of timber, designed for insertion into a mortise.
Examples of Mortise and Tenon Joint Use
Mortise and tenon joints have been used for thousands of years in a wide range of materials and a myriad of different structure types. Particularly famous examples of these include:
- A well near Leipzig in Germany, which is the worldâs oldest intact wooden architecture
- The Khufu ship in the Great Pyramid of Khufu, in Egypt
- Beams, brackets, roof frames, and struts in traditional Chinese architecture
- The sarsen stones of Stonehenge
- Assembling hull planks and other watercraft components in ancient shipbuilding
Where Are Mortise and Tenon Joints Used Today?
Modern construction also makes use of mortise and tenon joints. It is common to find them being used in:
- Furniture (especially tables and beds)
- Doors
- Windows
- Different roof components
As mortise and tenon joints can be found in iron and stone as well as wood, they are commonly used by stonemasons and blacksmiths as well as carpenters and builders.
Types of Mortise and Tenon Joints
At English Heritage Buildings, we will normally use a standard mortise and tenon joint for most projects, but many different types can feature in construction:
Blind Mortise and Tenon Joints
This type has the strength of an ordinary mortise and tenon joint but has the appearance of a butt joint. The mortise does not extend completely through the stile, which means that the tenon isnât visible when the pieces are assembled.
Coped Mortise and Tenon Joints
This type of joint involves all the frame members having a moulded profile on the inside edge, which will then be jointed to the panel. The result of having this joint in place is an elegant, tight-fitting, and durable design with advantageous strength.
This design is more typically used for intricate work, such as frames around glass doors and windows.
Housed Mortise and Tenon Joints
This type is often used to create both buildings and furniture because of the added strength it provides to the joints. This is the type of mortise and tenon joint that we will use when creating oak floor joists.
Notched Mortise and Tenon Joints
Also known as âhaunchedâ mortise and tenon joints, this type has a very short tongue which extends from the shoulder of the rail and the tongueâs edge. The type itself was created in order to fill the void that other mortise and tenon joints would leave in construction.
Types of Mortises
Individual types of mortises include:
- Open mortises; mortises with only three sides.
- Stub mortises; shallow mortises, the depth of which depends on the size of the timber. They are also mortises which don’t go through the workpiece.
- Through mortises; mortises that pass entirely through a piece.
- Wedged half-dovetail; a mortise which is wider or taller in the back than in the front or opening. The space for the wedge initially leaves room to insert the tenon. The wedge, after the tenon is engaged, prevents its withdrawal.
- Through wedged half-dovetail; a wedged half-dovetail mortise that passes entirely through the piece.
Types of Tenons
Individual types of tenons include:
- Stub tenons: short tenons, the depth of which also depends on the size of the timber. Itâs also a tenon that is shorter than the width of the mortised piece so the tenon doesnât show.
- Through tenons: tenons that pass entirely through the pieces of wood they are inserted into, being completely visible on the rear side.
- Loose tenons: tenons that are a separate part of the joint, as opposed to fixed tenons which are an integral part of one of the pieces to be joined.
- Biscuit tenons: thin, oval-shaped pieces of wood that resemble the shape of biscuits.
- Pegged (or pinned) tenons: common in timber framing joints, the joint is strengthened by driving a peg or dowel pin through one or more holes drilled through the mortise side wall and tenon.
- Teasle tenons: the tenons on top of jowled or gunstock posts, typically received by the mortise in the underside of a tie beam.
- Tusk tenons: these were a popular type of through tenon in decades past, and are still used in some designs today. The tenon extends past the end of the mortise material and a hole added to the side of the tenon accepts a wedge or pin.
- Top tenons: tenons that occur on top of a post.
- Hammer-headed tenons: a method of forming tenon joints when the shoulders cannot be tightened with a clamp.
- Half shoulder tenons: asymmetric tenons with a shoulder on only one side. A common use of these is in framed, ledged, and braced doors.
Advantages of Using Mortise and Tenon Joints
There are many advantages to using different types of mortise and tenon joints in construction:
A Classic Aesthetic
When combined with a timeless material like timber, mortise and tenon joints offer building projects a stunning aesthetic appeal that blends seamlessly with any building style, modern or traditional. They can be used in a range of different construction project types, in everything from furniture to full buildings and architectural structures.
Cost-Effectiveness
As mortise and tenon joints are only likely to be made of one material, they are very cost-effective. The money saved can then be used on other parts of a project.
Durability
Over time, mortise and tenon joints become more durable as their components become more settled and sturdier in the same way as timber.
Ease of Assembly
The relatively simple design of a mortise and tenon joint also means that they are easy to put together. This allows for a swift, straightforward build and installation of any structure and means you will be able to enjoy your new feature as soon as possible.
No Visible Gaps or Cracks
When professionally created, mortise and tenon joints will not leave visible gaps or cracks along the seams of the build. This prevents damage over time and helps to keep out cold air.
Strength
Mortise and tenon joints are one of the strongest joints you will find. The flush-fitting design means that they are extremely difficult to separate once put together.
Water Resistance
With the right sealant, mortise and tenon joints are capable of being water-tight. They are ideal for joints that often face the elements, like those on outbuildings and extensions.
Disadvantages of Using Mortise and Tenon Joints
Though mortise and tenon joints are one of the strongest and most versatile joints that can be used, they are not suitable for use everywhere. There are some factors which act as disadvantages:
Cannot be Used on Curved Surfaces
Mortise and tenon joints are only suitable for use on square or rectangular builds. Creating curvature can be difficult and therefore creating rounded features may not be possible.
The Possibility of Joint Failure
Mortise and tenon joints involve cross-grain joinery when created from wood. This introduces the risk of joint failure due to seasonal wood movement. Experienced craftsmen will be able to accommodate for this, though, by considering:
- Tenon length
- Tenon width
- Tenon thickness
How We Make Mortise and Tenon Joints
There are several methods and many step-by-step guides on how to make a mortise and tenon joint by hand. However, these often require time and tools that you may not have. It is also possible that doing them by hand without previous experience will lead to errors that could prevent the joint from fitting properly or become weakened (if not cut correctly).
At English Heritage Buildings, we create our products using state-of-the-art machinery that offers precision accuracy and rules out human error when cutting timber. This ensures that every piece fits together perfectly when the time comes for a build to be installed. It also allows for a clean finish on every part â including all mortise and tenon joints.
Buy a Build with Mortise and Tenon Joints
If you are intending to build a brand-new space for work, leisure, or storage on your property and have been considering incorporating mortise and tenon joints into the design, contact us. Our friendly team will be waiting to speak to you about designing and building a beautiful feature for your home. These may be ready-made from our collection of designs or completely bespoke.
Get in touch with us and let us help you design the perfect installation for your property.
