Wall panelling set-out: rails, stiles and panel widths

At a glance

Millimetres unless stated. The ranges are conventions, not standards: we found no standard or primary source that fixes any of them.

Set out in six steps

Set-out is a short piece of arithmetic done in a fixed order. Heights come first because they are fixed by the room; the horizontal division comes last because it is the only thing left to adjust. The letters are those in the drawing below.

• 1. Measure. Take the clear wall length L between the corners (or to the edge of an architrave) and the height to the ceiling. Measure the length at skirting height and again at the top of the panelling: old walls are rarely parallel.
• 2. Fix the heights. Choose the panelling height H, to the top of the dado rail or cap, and tie it to a datum such as the window stool. Choose the bottom rail b (the skirting may serve) and the top rail t. The panel height is then h = H − b − t.
• 3. Choose the stiles. Choose one stile width s for every stile between panels, and the visible end stile e (it can equal s). Make the end stiles a little wider than drawn, so they can be scribed to the wall and still show e. We use 10 mm as the example allowance.
• 4. Pick the panel count. Decide a target panel width from the proportion you want (h divided by the width), then count: n = (L − 2e + s) ÷ (target + s), rounded to the nearest whole number.
• 5. Solve for the true panel width. p = (L − 2e − (n − 1) × s) ÷ n. If that is not a whole millimetre, round it down and share the remainder between the two end stiles, half each, so every panel stays equal.
• 6. List the joint lines. The centre of the kth stile is e + p + s/2 + (k − 1) × (p + s) from the corner. Put them on the drawing as a dimension string, and put any joint in a long rail or cap on a stile centre.

Worked example: a 4,830 mm wall

A wall 4,830 mm long between corners, with a ceiling at 2,700 mm. The panelling is 1,100 mm high with the window stool level with its top. The bottom rail is 150 mm (the skirting), the top rail 90 mm, so the panel height is 1,100 − 150 − 90 = 860 mm. Stiles and end stiles are 70 mm. We want panels near 525 mm wide.

• Count: n = (4,830 − 140 + 70) ÷ (525 + 70) = 4,760 ÷ 595 = 8. Eight panels.
• Width: p = (4,830 − 140 − 7 × 70) ÷ 8 = 4,200 ÷ 8 = 525 mm, a whole number, so no remainder goes to the end stiles.
• Proportion: 860 ÷ 525 = 1.64, so each panel is about 1.6 times as tall as it is wide.
• Symmetry: eight is even, so the wall centre (2,415 mm) falls on the centre of the fourth stile. The window, centred on the wall, shares that line.

The same wall with other panel counts

The same wall can be divided differently. Each count gives its own panel width and proportion, and it decides whether the centre line lands on a stile or a panel. Fix the proportion you want first; the arithmetic then picks the count.

Panel height is 860 mm in every row, and stiles and end stiles are 70 mm. Where the width is not a whole number, round it down to a whole millimetre and add the remainder to the end stiles, half each (for n = 9, p = 458 and each end stile grows by 4 mm).

A quick look-up for other wall lengths, with the same stiles and a target panel near 525 mm:

Heights: where the panelling stops

No standard fixes the height of a dado or of panelling, and the guidance that exists is a mixture of classical proportion and modern habit. A fixed point does help: the panelling height is the first number in the sums above, so it has to be settled before anything else.

• A fifth to a third of the room. The dado is the middle part of a classical column pedestal carried along the wall, and the cap on it is the dado rail. One writer reports that some authors put the pedestal at a fifth of the height of the order and others at a third, and that a Georgian pattern book, Swan's Georgian Architectural Designs and Details (1757), gives 2 ft 5 in (about 737 mm, or roughly a quarter) for a dado in a 10 ft room, adding about three quarters of an inch for each foot of room height above that. Another eighteenth-century author is reported as saying the proportion is not fixed and should suit the room.
• One writer's range. The same writer puts a dado or chair rail somewhere between 26 and 32 inches (about 660 to 810 mm). Modern decorating and kit guides more often quote 900 to 1,100 mm. None of the modern sources we saw gives a primary source.
• Line it up with something. The same article says Georgian and Federal builders set the cap of the wainscot at the height of the window stool, so one line ran round the room. That is a better test than any ratio: look for a stool, a door head or a fixed piece of furniture in the room and make the panelling meet it.
• Tall panelling is another job. Where the panelling runs to the cornice, the wall is divided into tiers, and the sums above are repeated for each tier with the stile lines running straight through. Our panelling styles sheet draws a three-tier wall.

For a feel of the range, this table works the three fractions out for common ceilings, rounded to 5 mm. It is arithmetic on ratios in circulation, not a rule.

Corners, doors, windows and the centre line

Walls are not clean rectangles, and the awkward parts are where a set-out is won or lost. The drawing shows the four cases that come up most.

• Internal corners. Decide which wall runs through to the corner and let the other butt to the face of its panelling, so there is no mitre in the corner. Measure the end stile e from that face. Where a stile meets an out-of-true wall it is made wider than drawn and scribed, and the allowance (10 mm in our example) is written on the drawing.
• Doors. Keep every panel the same width and let the stile beside the architrave take the remainder. For a run from a corner to the edge of an architrave, d = run − e − n × p − (n − 1) × s; choose the largest n for which d is still at least s. The alternative, letting the architrave stand in for a stile, saves a joint but fixes the last panel's width to the opening.
• Windows. Take the cap to the window stool where you can. Centre the panelling on the window: with an even panel count the centre line passes through a stile, with an odd count through the middle of a panel. Choose the parity first, then the count.
• Around the room. Set the room out as a loop, not wall by wall. Start with the wall the eye reaches first, make that one symmetrical, and let any awkward remainder fall on the least visible wall, such as the one behind an opening door.

What to put on the drawing

• One set-out drawing per wall. Show L, the heights H, b, h and t, the stile widths, the panel width and count, and the stile-centre string. Show the datum the height comes from.
• Say which dimension is allowed to move. Panels equal within a stated tolerance; the remainder goes to the end stiles or to the stile beside a door, and nowhere else.
• Write the scribe allowance on the drawing and say who scribes, workshop or site fitter.
• Approve the set-out before cutting. A wall that has been surveyed twice and set out once costs less than panels cut to the wrong count.
• Solid timber moves. Our journal guide on bespoke panelling notes that solid timber breathes with the humidity of the room, so give the workshop the conditions where tight joints are drawn.

Panelling is also a question for fire regulation in England: it is not among the narrow members that Approved Document B leaves out of the wall-lining classification, whereas fitted furniture is excluded (Volume 1 paragraph 4.3, Volume 2 paragraph 6.3; 2019 edition incorporating the 2020, 2022, 2025 and 2026 amendments). The wall behind the panelling is a lining either way, and the fire engineer or building control decides the class. This sheet gives none; the fire section of our moulding profiles sheet sets out what we read. We coordinate the set-out drawing with the partner workshop before the schedule is fixed.

Panelling [1,100] mm high to the top of the [dado rail / cap] from finished floor level, aligned with [the window stool / door head]. Set out symmetrically about [the wall centre line]; panel widths equal within [1] mm along each wall; joints on stile centres. Stiles [70] mm, visible end stiles [70] mm, top rail [90] mm, bottom rail [150] mm, panel height [860] mm, as set-out drawing [no.], approved before production.

End stiles made [10] mm wider than shown and scribed to the wall on [site / in the workshop]. At [internal corners] [wall B] runs through and [wall A] butts to it. At doors the stile beside the architrave takes up the remainder of the run and is not less than [70] mm; panel widths do not vary.

Where the wall does not divide into equal panels at the width specified, the count is set to the nearest whole number, the width adjusted and the revised set-out approved before production. A drawn dimension governs over any proportion rule.

Standards and sources

• Gary Katz, Correct Height for Chair Rail and Wainscot, Journal of Light Construction, 31 July 2017: read 5 November 2026; source of the dado ranges, pedestal fractions and Swan figure as reported there (the pattern books were not read).
• Approved Document B Volumes 1 and 2 (England), 2019 edition with amendments to 2026: Volume 1 paragraph 4.3; Volume 2 paragraph 6.3 (what a wall does not include). Read November 2026.
• BS 1186-3, wood trim and its fixing: named only; not read. No set-out rule is claimed from it.

Questions we are asked

How do you divide a wall into equal panels?

Fix the heights first. Then choose the stile width s and the end stile e, pick a target panel width, and count n = (L − 2e + s) ÷ (target + s), rounded. The true width is p = (L − 2e − (n − 1) × s) ÷ n. Round it down to a whole millimetre and share the remainder between the end stiles.

What width should stiles and rails be?

No standard fixes them. One modern guide quotes stiles of 50 to 70 mm and a top rail of about 90 mm, without a primary source. Choose from the proportion you want and the fixing and moulding the workshop will use, set one stile width for the wall, and dimension it on the drawing.

What height should wall panelling or a dado be?

There is no standard. Classical proportion puts it at a fifth to a third of the room height; one writer gives 26 to 32 inches (about 660 to 810 mm) and modern guides 900 to 1,100 mm. Pick a datum in the room, such as the window stool, and make the panelling meet it.

What is the best proportion for a panel?

We found no authoritative ratio. Square, three to two and about 1.6 to one are all used, and taller panels read as more formal. Work out the proportion each panel count gives for your wall and choose the one that suits the room.

Should the window be centred on a panel or a stile?

Either works if you choose it deliberately. With an even number of panels the wall centre falls on a stile centre; with an odd number it falls on the middle of a panel. Choose the one you want, then the matching panel count.

Where should joints in rails and capping fall?

On a stile centre, where the stile hides them, and never part way across a panel. Put the stile-centre dimensions on the drawing so the workshop and the fitter work from the same positions.