Rough Sawn Timber or PSE or PAR
First the the jargon.
Rough sawn or just sawn is the cheapest and easiest to understand, its roughly sawn to the size stated. It's cheaper because the Timber Merchant hasn't had to do any expensive machining to it.
PSE, Planed Square Edge or PAR Planed All Round, as far as I can tell PSE and PAR are interchangeable. Suppliers use both to described timber that has been planed on all four sides.
What to choose Sawn or PSE/PAR ?
I’ve got a planner thicknesser so I'd have rough sawn timber in most circumstances. This allows me to machine the timber to the exact dimensions I need after its acclimatised, (dried out to the right level). (Another page on this). It’s also cheaper!
PSE/PAR will still need some finishing to get a smooth surface. More importantly when its dried out a bit more the dimensions will have changed and it often distorts requiring planing to get it back to straight and square.
With PSE /PAR the dimensions are given as the nominal sawn size before it’s been planned.
SO BE AWARE You might think you are buying 50 x 100mm but the actual size could be as small as 45 x 95mm.
Having said that, PSE comes in handy if it is the right size off the shelf.
This brings us nicely to timber sizes.
Next - Commonly available rough sawn and PSE / PAR timber sizes
Timber / wood for DIY, Woodworking, Joinery, Carpentry
Examples of joinery jobs, softwood types and timber grades
Carpentry and joinery softwood types
Timber Grades, Unsorted ? Vth's ? Sawfallen ?
Timber rough sawn ? PSE ? PAR?
Commonly available rough sawn and PSE / PAR timber sizes
How to choose a Timber Merchant / Supplier
Work out what timber you need for the job
Inspecting wood at the Timber Merchant
Preparing the timber for acclimatising
Planing timber / wood flat, square and true
How to plane up the good pieces of wood
How to plane Winding or Twisted timber
How to plane bowing on a timber board
How to plane cupped or cupping timber