If you’re planning an oak framed extension, garage, garden room or new home, you’ll probably come across a few unfamiliar oak frame jargon along the way.
Words like purlin, tie beam and mortise and tenon can make oak framing sound more complicated than it really is.
Here’s a simple guide to some of the most common oak frame terminology.
Brace
A brace is a diagonal piece of oak used to strengthen and stabilise the frame.
Braces can be straight or curved and often become an important visual feature of an oak framed building.
Scarf joint
A scarf joint is used when two pieces of timber need to be joined together to create a longer continuous section.
The ends of the timbers are shaped so they overlap and interlock, helping them work together as one longer beam.
Mortise and tenon joint
The mortise and tenon is one of the most traditional joints used in oak framing.
The tenon is a shaped projection on the end of one timber, while the mortise is the matching slot cut into another.
The two fit together to create a strong connection, usually secured with an oak peg.
Oak peg
An oak peg is used to secure traditional timber joints.
In many oak frames, the peg holes are deliberately positioned slightly out of line so that driving the peg through pulls the joint tightly together. This is known as a draw-bored joint.
The exposed pegs also form part of the traditional appearance of an oak frame.
Oak truss
An oak truss is the structural framework supporting the roof.
There are several different truss styles, including king post, queen post, raised tie and scissor trusses.
The right design depends on the span, structural requirements and the look you want to achieve.
You can explore different styles on our Oak Trusses page.
Principal rafter
A principal rafter is one of the main sloping structural timbers in an oak roof or truss.
It forms part of the primary roof structure and helps transfer the roof load down into the frame below.
Purlin
A purlin is a horizontal roof beam running along the length of the building.
It supports the rafters and is often clearly visible inside vaulted oak framed spaces.
An easy way to remember the difference is:
Rafters run down the roof. Purlins run along it.
Tie beam
A tie beam is a horizontal timber running across the lower part of a roof structure.
It helps hold the two sides of the frame together and prevents the roof from pushing the walls outwards.
Green oak
Green oak simply means oak that has been relatively recently felled and still contains a higher level of natural moisture.
It is widely used in structural oak framing because large sections can be machined and jointed effectively while the timber is still green.
As the oak dries, some natural movement, shrinkage and splitting should be expected.
Shakes and splits
As oak dries, small or sometimes quite noticeable splits can appear along the grain.
These are known as shakes and are a natural characteristic of structural oak.
They do not automatically indicate a fault with the timber. A properly designed oak frame allows for this natural movement from the outset.
CNC machining
CNC stands for Computer Numerical Control.
At Vestra Oak, CNC machinery is used to precisely machine the joints, holes and details required in each piece of timber.
This combines traditional oak framing techniques with modern manufacturing, helping us produce accurate bespoke frames ready for assembly on site.
Making oak framing easier to understand
Oak framing has centuries of history behind it, but the oak frame jargon doesn’t need to make your project difficult to understand.
Once you know the basic terms, drawings and quotations become much easier to follow.
At Vestra Oak, we believe you should understand exactly what is being designed and supplied before your frame reaches site. Our team can guide you through the process, from the initial drawings through to the finished oak frame kit.
Planning an oak framed project? Explore our range of bespoke oak framed structures or speak to the Vestra Oak team about your plans.