As builders we use S.A Pine every day but do we know the difference between Rough Sawn, Fine Sawn and PAR timber?
Rough Sawn Timber
This is the most cost-effective of the three types of timber and comes as originally cut without smoothing or sanding to the standard size of the circular saw. This is the first stage that you would receive the timber at, from the mill, before any further work is done on it. This timber is ideal when it’s used on a site where it can’t be seen and the surface finish is not important. The timber will also vary in width and thickness throughout the length and breadth of the plank.
Fine Sawn Timber
Also known as sized timber, this type of timber has typically been cut a second time. This gives a much smoother finish to the timber and is approximately 2mm to 3mm smaller than the standard size. For example, a sized batten rough sawn is 38 x 38 while fine sawn is 36 x 36. An allowance of 3mm to 4mm should be allowed in variation through the length and breadth of the plank after treating sized timber. Lastly, it is important to note that the neatness of the sizing of the timber can vary from mill to mill.
Planed all round (PAR) means all flat surfaces are planed. Planed square edge means you have one edge planed straight and can measure from there. It’s one step up from fine sawn. The secret in the consistency of the planing thicknesses is the treating. This is because timber typically swells inconsistently across its length and breadth once treated so an allowance for 1mm to 2mm should be made. Timber typically swells less if it’s clear treated (TBTN) as opposed to green treated (CCA). TBTN treatment is not suitable for outside though.
Please see attached downloadable PDF table on timber sizes –
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