What does “planed all round” actually promise when you pick up a length of timber at the yard? If you have stood in a timber merchant holding a piece labelled PAR and wondered why it measures smaller than the shelf label suggested, the term itself holds the explanation. Planed all round sounds self-explanatory, but it carries practical detail that affects the finished size. Get that detail wrong and your project comes up short, literally.
This guide unpacks what PAR means, how it differs from rough-sawn and planed square edge stock, why the sizing convention trips people up, and how to buy the right timber the first time.
What Does Planed All Round Mean?
In British and Commonwealth timber trade usage, planed all round (PAR) describes timber that has been planed on all four sides, so the cross-section arrives as a finished rectangle. Every face you can see or touch has been machined smooth. There is no rough band along one edge, no sawn texture on the back face, and no surprises when you flip the board over.
That is the strict definition, and it is worth holding onto. The term is sometimes used loosely for any dressed timber, including moulded or profiled sections, even though strictly it means four flat faces. If a supplier describes architrave or skirting as PAR, check what you are actually getting. A profiled section is shaped, not simply planed flat on four sides.
PAR sits in a family of timber finishes that every buyer should recognise:
| Finish | Faces planed | Typical use |
|---|---|---|
| Rough sawn | None | Structural work, fencing, jobs where appearance does not matter |
| PSE (planed square edge) | One face and one edge | Carcassing where only some faces show |
| PAR (planed all round) | All four sides | Furniture, shelving, trim, visible joinery |
| Profiled or moulded | Shaped, not flat | Skirting, architrave, handrails, beading |
The distinction between PAR and PSE matters more than most beginners expect. PSE is planed on one face and one edge only, leaving the other faces rough. It is common for carcassing where only some faces are visible. PAR costs more because more machining and more waste are involved, but it saves you time at the bench.
Why the Finished Size Is the Size You Get
Here is the single most important thing to understand about PAR: PAR sizes are usually quoted as the finished size, while rough-sawn sizes are quoted as the size before planing. A piece labelled PAR 44 × 69 mm measures 44 × 69 mm when you receive it. A rough-sawn piece labelled 50 × 75 mm will be smaller than that once it has been planed down.
Planing removes material. That is the whole point of it. To produce a given PAR size, the mill has to start with rough-sawn stock that is larger, because every pass through the planer takes a shaving off. The exact amount removed depends on the mill and the standard applied, so there is no universal figure to memorise. What you can rely on is the direction of the logic: rough stock shrinks into finished stock, never the other way around.
This is where a lot of first-time buyers come unstuck. They order a “2 × 1” expecting something close to 50 × 25 mm and receive a piece that measures noticeably less. The metric figures used in UK timber retail for older imperial PAR sizes are approximations, not exact conversions. A “2 × 1 inch PAR” sold under a metric label will not convert neatly, and the metric figure is not an exact conversion of the imperial one. Treat the label as a nominal trade name rather than a precision measurement, and measure the actual stock before you cut.
A practical habit that saves real money: take a tape measure to the yard, or ask the merchant for the actual finished dimensions in writing before you commit to a large order. For anything where fit matters, such as drawer runners, shelf housings or frame rebates, work from measured stock rather than the label. If you are planning a layout around fixed dimensions, the same discipline applies as when you weigh up different floor plan options for a room: the numbers on paper and the numbers on site are rarely identical, and the site numbers win.
Moisture Content and Movement You Cannot See
PAR timber may be supplied kiln-dried or air-dried, and planing is often done after drying. That sequence matters because moisture content affects final dimensions: timber shrinks as it dries. A board that measures perfectly on the day it arrives can move slightly as it acclimatises to your workshop or home.
For most indoor projects, the sensible routine is straightforward:
- Bring the timber into the space where it will live, or somewhere with similar conditions, a few days before you cut it.
- Stack it flat with spacers so air circulates on all faces.
- Measure again once it has settled, and cut to the new measurement.
- Seal or finish exposed end grain promptly, because end grain takes up and releases moisture far faster than face grain.
People who skip step one often find that a snug joint becomes a loose one, or a flat panel develops a cup, within a week or two. It is not a defect in the timber. It is normal wood behaviour, and planning for it is part of working with a natural material.
Rough-Sawn Versus PAR: Which Should You Buy?
The honest answer is that it depends on how much machining you are set up to do and how visible the timber will be. Rough-sawn stock is cheaper per cubic metre because less work has gone into it, but you pay for that saving in labour, dust and time. If you own a thicknesser and a jointer, buying rough and machining it yourself gives you control over final dimensions and often better value on larger jobs.
If you do not have that machinery, PAR is the pragmatic choice. It arrives flat, square and ready to mark out. The premium you pay is essentially a convenience and equipment charge.
There is a middle path worth knowing about. For carcassing where only some faces show, PSE is often the smart buy: you get a clean face and edge where it counts and rough faces hidden inside the structure. Buying PAR for everything is a common beginner mistake, and an expensive one on a big framing job.
Another mistake is assuming PAR arrives perfectly flat and square every time. Planing produces a finished rectangle in cross-section, but long lengths can still carry a slight bow, twist or spring, especially in faster-grown softwoods. Check every length on a flat surface before you start cutting, and set aside any piece with a twist for shorter components. Buying an extra length or two as insurance is cheaper than a second trip to the yard.
Reading the Standards and the Small Print
In the UK, softwood sizes and tolerances have historically been covered by British Standards in the BS 4978 and BS EN 336 family, with BS EN 336 addressing tolerances for structural softwood. Which current standard specifies PAR tolerances is a detail worth confirming with your supplier or a current standards document before you rely on it for a specification, because standards are revised and editions change.
For most buyers, the practical takeaway is simpler than the standards paperwork: ask the merchant what tolerance applies to the stock you are buying, and whether the quoted size is the finished size or the nominal size. A reputable yard will answer both questions without hesitation. A vague answer is your cue to measure before you buy.
It also helps to know what you are buying the timber for. Structural uses have different requirements from decorative ones, and mixing the two categories is a classic error. A planed board chosen for appearance may not carry the grading or tolerance you need in a load-bearing position. Conversely, paying for structural grade on a decorative shelf is money wasted.
Where PAR Fits in Real Projects
PAR earns its keep wherever the timber stays visible and the finish matters. Shelving, bookcases, window boards, trim, batten details, simple furniture frames and children’s play items all benefit from four clean faces. The smooth surfaces take paint, stain and oil evenly, which is not true of rough-sawn stock where the sawn texture drinks finish unevenly and shows through.
It is also the friendlier option for anyone working with hand tools or in a small space. No planer means no chip extraction, no noise and no shavings across the workshop floor. For a hobbyist building a project in a spare room or on a balcony, that difference is decisive.
Where PAR is less obviously the right call is in hidden structural work, outdoor framing and anything that will be painted and never inspected closely. In those settings, the premium buys you little. The same logic applies to choosing finishes and fittings generally: spend where it shows, save where it does not. It is a principle that turns up everywhere, from picking a destination for a family trip out of a list of the best places to visit for Christmas to shortlisting baby names from around the world when you only need one: the shortlist does the work, and the extras are optional.
One more practical note on buying. Timber is a natural product, and two boards from the same pallet can differ in colour, grain and weight. If a project needs matching pieces, buy them all in one visit from the same batch rather than topping up later. Colour and grain matching across separate deliveries is a gamble, and PAR stock in particular can vary noticeably between packs.
Common Mistakes and What Actually Works
The mistakes repeat themselves across every timber yard and every weekend workshop. Here are the ones that cost people the most time and money, with the fix for each.
Trusting the label over the tape. Nominal sizes and finished sizes are different things. Measure the stock, write the real dimensions on the cutting list, and work from those. This single habit prevents most sizing disasters.
Buying PAR for hidden framing. It is a waste of money. Use PSE or rough-sawn for anything that will be covered, and save the planed stock for visible surfaces.
Cutting before acclimatising. Timber moves as it settles into a new environment. Give it a few days in the space where it will live, then measure and cut. Skipping this step causes joints that open and panels that cup.
Assuming every length is straight. Check each piece on a flat surface. Sort out twisted lengths for short components and keep the straightest stock for the longest spans.
Ignoring end grain. End grain absorbs moisture far faster than face grain. Seal or finish cut ends promptly, especially on exterior or damp-adjacent work.
Buying in dribs and drabs. Match colour, grain and batch in one purchase where appearance matters. Topping up later rarely matches.
What actually works is unglamorous: measure the real stock, buy the right grade for the job, let the timber settle, and keep a couple of spare lengths in the rack. None of it is clever, and all of it saves money.
Conclusion
Planed all round is a small phrase with a lot riding on it. It means four flat, machined faces and a finished rectangular cross-section, and it usually means the quoted size is the size you will actually hold in your hand. Understanding that convention, along with the difference between PAR and PSE, the role of moisture content, and the limits of nominal labelling, turns timber buying from a guessing game into a straightforward transaction.
Buy PAR where the timber shows. Buy rougher stock where it does not. Measure before you cut, let the wood settle, and check the standards question with your supplier if a specification depends on it. Do those things and the timber will do its job quietly for years, which is exactly what good material should do.
Frequently Asked Questions
What does planed all round mean in timber?
It means the timber has been planed on all four sides, so the cross-section is a finished rectangle with smooth faces throughout. It contrasts with rough-sawn timber, which has no planed faces, and with planed square edge (PSE), which is planed on only one face and one edge.
Is PAR the same as PSE?
No. PAR has all four faces planed. PSE has one face and one edge planed, leaving the remaining faces rough. PSE is common for carcassing where only some faces are visible, while PAR is used where the timber will be seen and finished.
Why is PAR smaller than the size I ordered?
Because planing removes material, and PAR sizes are usually quoted as the finished size. A piece labelled PAR 44 × 69 mm measures 44 × 69 mm when you receive it. Older imperial sizes sold under metric labels are approximations rather than exact conversions, which adds to the confusion. Always measure the actual stock before cutting.
Should I buy PAR or rough-sawn timber?
Buy PAR when the timber will be visible and you want a smooth, ready-to-finish surface without machining it yourself. Buy rough-sawn or PSE when the timber will be hidden, when you have the machinery to thickness and joint it, or when cost matters more than convenience on a large job.
Does moisture content affect PAR timber?
Yes. PAR may be supplied kiln-dried or air-dried, and planing is often done after drying. Timber shrinks as it dries, so dimensions can change slightly after delivery. Let the stock acclimatise in the space where it will be used for a few days, then measure again before cutting.
Does planed all round timber arrive perfectly straight?
Not always. Planing produces a finished rectangle in cross-section, but long lengths can still carry a slight bow, twist or spring, particularly in faster-grown softwoods. Check every length on a flat surface before cutting, and reserve the straightest pieces for the longest spans.
