A Layman's Guide to Joinery Facts and Figures

I myself am fairly new to the joinery manufacturing business and its been a steep learning curve. The people I work with know their trade and babble away in "joinery" speak while I sit there trying to comprehend it all.

The first and probably most unusual idea to come to terms with is the use of imperial and metric- usually in the same sentence! For example- "I need 3 pieces of PSE softwood, 22mm x 10mm, 4 No @ 6 '".

This to the average person is nothing short of another language. To explain- PSE is PLANED SQUARE EDGE timber. Buying timber this way means that you have a square edge to measure from but it is more expensive. Most of the timber bought by manufacturing companies is rough sawn, IE straight from the timber merchants and cut a little oversize, generally with some bark still attached and the usual defects.When ordering timber, a certain amount of waste is taken as standard. Cutting the ends to square up the timber is the first stage. Then several passes through a 4 sided planer which reduces the thickness of the timber closer to the required size and removes the bark. The edges may need running over a planer / thicknesser to square them up too.

In joinery – it is generally good practice to give the width measurement first, so in the above example-22mm wide and 10mm deep. This is especially important if the 2 measurements are very close, getting it wrong means that whatever you are making will not fit properly. Measure twice cut once!

4 No is of course how many you want- fairly self explanatory.

Then 6 'in length! We just can not get away from using imperial. Just think- if someone asks how tall you are- the usual reply is 5 '3 "or 6' 2". We do not say- I'm 1580 tall or 1860. People just know what you mean.

Its the same in joinery- 5mm, 15mm, 1 metre, half inch, 2 foot- it all gets used. Basically- most companies will work with either metric or imperial- so do not be worried. Metric is more accurate- using millimetres means less chance for mistakes.

When we purchase hardwood it is measured in cubic feet and when ordering softwood we buy in cubic metres, which all adds to the fun and games!


There are several different types of window and style- we shall concentrate on 3. The traditional window, stormproof and sliding sash.

The first two are quite similar in many ways- the main exception is the sash's. The sash is the opening or non opening extra frame surrounded by the outer frame. On traditional windows there is often a sash even when it is non opening and this gives an overall balance to the window look. The opening sash lies flush with the frame. On a stormproof window- often found on more modern houses or in areas of harsh weather- the sash frame wraps around the main frame, overlapping it to give extra protection.Both types of window will have hinges of some description allowing the sash to open.

The sliding sash is found on many historic and listed buildings, and generally has two sash's which can slide up and down depending on requirement. Is does not have hinges, but works on weights and cords to lift and drop the heavy sash's. Modern sliding sash windows utilise a spring instead of the weights making for easier use and reduced frame size. There are also "Mock" sash windows which look like normal sliders but work on a friction hinge- see my article on sliding sash windows for more information.

The frame is the outer timbers comprising 2 side pieces called jambs and a top piece called the head and the bottom section called the cill or sill. The sash itself is made up of 2 vertical stiles and 2 horizontal rails. Muntins are the name given to both horizontal and vertical dividing bars which split the window glass into individual panes or lights.

Most good joinery companies will be happy to show you their work and discuss your requirements. Just remember when choosing- not all windows are the same- check out the timber, the frame section sizes and the finish.


All doors are not created equally either- many exterior doors are neither solid or well made. Standard thickness is around 44mm, so be sure to check out what you are getting for your money.

The basic door construction is a frame – comprising 2 side stiles and a top and bottom rail. There are many variations to the actual make up of the door- but transoms are the horizontal timbers and mullions are the vertical timbers. Infills can be solid panels- such as raised and fielded- which are very common and give a central flat panel with sloping edges, or possibly glazed units in a huge number of variants, including leaded glass, obscure and super efficient double glazing. Glass for doors must be either toughened or laminated to conform to building regulations- do not accept anything less.

Also check that mortice and tenon joints are used in the construction, as many companies try to save money but using inferior jointing methods. A well made mortice and tenon joint, glued up will be stronger than the surrounding timber and should never come apart.

The timber is also important- TEC wood is a laminated timber (which means it has layers glued together for strength and stability) which is being used extensively. Timber choice in the UK should be a hardwood such as Sapele or European Oak. Idigbo and Iroko are also good choices. Ask your joinery company for their advice on whats best in which situation. Budget will also play its part, but there are always options.

A rebate is a groove cut in either the edge of the timber- EG where doors shut together or can be a cut in a flat panel to take another panel.

I hope this article has been informative and if you need any advice, check out our website or contact us.