Robinia waney-edge cladding – farm buildings and sheep sheds

Ferdinand Terlinden

1 day ago

9 min read

Robinia series · Choosing by use

Cheaper than finger-jointed cladding and simpler to fix, but rustic — and what robinia changes about it

A waney-edge board — the boards the French call planches canadiennes — is a board edged on one side only: one edge sawn straight, the other left as the log gave it, with its wane, the rounded edge of the trunk. That is the difference from an unedged board, which keeps both natural edges. Compared with cladding in finger-jointed boards, it costs less and is simpler to fix: no interlocking profile, no setting-out to the millimetre. In exchange, the look is distinctly more rustic. At Acacia Bois: 0.5 to 4 m long, 10 to 40 cm wide (width measured at the middle, bark to bark), 20 to 22 mm thick for cladding, in AB or C grade — and 2 m maximum in the sanded version with sapwood removed.

In robinia (Robinia pseudoacacia) — also known as black locust, and often sold as acacia — waney-edge cladding meets use class 4 (EN 335) with no treatment at all: it goes up as it is on a sheep shed, a barn or a shelter, with no biocide in contact with the animals. When ordering, work in square metres, the unit we sell in: start from the wall area, add about 25 % because the boards overlap, then 10 % for sorting and offcuts. Allow roughly 1.4 m² of boards for every 1 m² of wall covered.

10 to 40 cm wide

The width follows that of the log: that is what makes the product economical, and what makes sorting necessary before fixing.

Exterior cladding in robinia waney-edge boards, natural log edges visible — Robinia waney-edge cladding: each course keeps the natural edge of the log along one side. Sorting by width, before fixing, is what decides how even the wall looks.

Waney-edge board, edged board, profiled cladding: what is the difference?

An edged board has both edges sawn parallel. Getting that shape forces the sawyer to cut material off each side along the whole length — a heavy loss on robinia, which grows crooked, that is to say curved. A waney-edge board is edged on one side only: the straight edge gives a reference line when fixing, the natural edge absorbs the curve of the log. High yield from the log, lower price per square metre. The first cut taken under the bark, edged on neither side, is called the slab.

Profiled cladding is a third product: boards planed on four faces, rhombus or tongue-and-groove profile — our finger-jointed boards, covered in "Finger-jointed robinia decking and cladding – stable and durable". The vocabulary is not fixed: in French, planche canadienne means the natural-edge board in Belgium and northern France, while elsewhere bardage canadien means a bevelled board profiled in the factory. Ask for the product's technical data sheet before you order: ours give the dimensions, grades and exact profile of each range.

Unedged robinia boards 22 mm thick, sorted in the workshop before dispatch — Boards 20 to 22 mm thick: on overlapping cladding, the thickness of each board adds to that of the course below — keeping it thin is what keeps the cladding flat against the wall.

What does robinia change about waney-edge cladding?

Standard waney-edge cladding is in spruce, Nordic redwood or Douglas fir: these species top out at use class 3, so they either go through pressure treatment or need replacing within ten to fifteen years.

Robinia reaches durability class 1-2 (EN 350), and therefore use class 4 (EN 335) without any treatment: around 30 years in ground contact, longer on a ventilated wall. Our Romanian robinia, sawn at Teiu, Hunedoara County (Romania), has a density of around 740 kg/m³. In a livestock building, that means no biocide where the animals lick and gnaw the wood, and maintenance limited to cleaning.

How do you fix waney-edge cladding?

First step: remove any bark left on the wane. Robinia bark comes loose as it dries, holds water and harbours insects; a pass with a drawknife or a wire brush on dry wood is enough. A debarked edge greys cleanly; an edge left with bark flakes off in patches within two winters.

Horizontal overlapping boards are the norm on farm buildings; vertical fixing, board-on-board or board-and-batten, calls for horizontal battens with ventilation openings cut into them. In every case the cladding is fixed to battens — the timber strips that hold the boards off the wall — of 24 mm minimum, at 40 to 60 cm centres (the distance from centre line to centre line), with the ventilation gap open at top and bottom and the first board 20-30 cm above the ground.

Thickness matters more than you might think. Our cladding boards are 20 to 22 mm, and that thinness is deliberate. At each overlap, the upper board is lifted by the full thickness of the one below: the thicker the board, the more it tilts and the further the cladding stands off the wall, course after course. A thin board stays almost flat, the face of the wall stays straight and the fixing works in line.

Fix the straight edge downwards, as the reference line, and let the natural edge receive the next course. Set the overlap from the narrowest board in the batch, never from the average width: 4 cm on a natural edge, against 15 to 20 mm on a machined board. Screws are stainless steel (A2/A4) without exception: robinia is acidic (pH ≈ 4.5) and corrodes ordinary steel. Pre-drill, and never drive a screw through both boards of an overlap: one line of fixings per board per batten, otherwise a 30 cm board will split in the first dry summer. See "Screws and fixings for robinia". Finally, allow for shrinkage: a board delivered fresh from the saw loses width as it dries. On overlapping cladding, this shrinkage is taken up by the overlap itself — one more reason to make it generous — but a board held by two lines of screws or pressed tight against its neighbour will eventually split or open up.

Sheep sheds and livestock buildings: how good is waney-edge cladding?

In a sheep shed, cladding cuts the wind without closing the building in, lets moisture out and takes knocks. Humidity rises quickly — animals, bedding, ammonia — and a timber wall ventilated from behind buffers these swings, whereas condensation runs down a steel sheet. As spaced boarding (what British farm builders call Yorkshire boarding), with gaps of 2 to 4 cm between boards, waney-edge cladding ventilates; overlapped, it closes in a storage area.

Sheep shed clad in robinia waney-edge boards with spaced boarding and a timber shingle roof — A new sheep shed clad in unedged robinia boards, under a timber shingle roof: the natural edges set the rhythm of the walls, the spaced boarding at the top ventilates the building, and nothing has been treated where the animals lick and gnaw the wood.

Robinia is a hard wood, and it stands up to a flock rubbing against it, the knock of a horn and gnawing far better than a soft softwood, without bringing in any chemicals. The toxicity of fresh bark is covered in "Robinia fencing and cleft palings – choosing by use": here the wood is debarked, and therefore inert.

Barns, shelters, screens: other uses

Beyond livestock, waney-edge cladding covers anything that does not need a machined facade: barns, lean-tos, garden sheds, garage cladding, the walls and base of planters, solid fences and privacy screens. On a screen, the irregular rhythm of the widths reads as a deliberate choice.

The look is rustic, and unapologetically so — wavy edge, saw marks, visible knots. Robinia goes from yellow-green to brown and then to silver-grey without losing its durability, a subject covered in "Greying and maintenance of robinia"; on a natural edge, this greying evens out the whole.

Which grade should you choose, and how much should you order?

Two grades in the catalogue. AB grade is the cleanest, with sound, limited knots: a privacy screen seen close up, an outbuilding people use. C grade accepts black knots and knots over 3 cm; on a sheep shed or a barn it does the same job for less, with identical durability.

A third option exists, outside the standard catalogue: the board sanded, with sapwood removed. The pale outer ring is taken off and the faces are sanded; only heartwood remains, smooth to the touch and free of splinters. This is the product asked for on the walls and low walls of playgrounds, school grounds and child-height shelters, wherever the wood is touched all the time — a use covered in "Playgrounds and school grounds in robinia (EN 1176)". One limit to know before you draw anything: sanded with sapwood removed, lengths stop at 2 m. Removing the sapwood along the whole length of a crooked board requires a straight, sound log over the whole piece, and beyond 2 m the sorting becomes too strict to be workable.

Unedged robinia boards, sanded with sapwood removed, stacked at the Teiu sawmill — Unedged board, sanded, sapwood removed: the pale outer ring is taken off, leaving only heartwood, smooth under the hand and free of splinters — this is the product asked for on the walls of playgrounds and school grounds.

The quantity is calculated in square metres, with two allowances. Start from the wall area to be covered, less openings. First add the overlap, because a board never shows its full width: the next course covers 4 cm of it. On 30 cm boards this costs 15 % more area; on 18 cm boards, 30 %. Allow 25 % for a mixed batch, which is the usual case. Then add 10 % for offcuts, sorting and rejected boards. In total, order about 1.4 m² of boards per square metre of wall: 100 m² of cladding needs roughly 140 m² of boards. If you think in volume, one cubic metre of 20 to 22 mm boards gives 45 to 50 m² of boards, or around 33 to 35 m² of finished wall.

It remains to say where this product is not suitable. The irregular width complicates the setting-out — the plan for arranging the boards on the wall — and means sorting on site: fixing takes longer. Lengths stop at 4 m, and at just 2 m in the sanded version with sapwood removed. The rustic look does not suit a contemporary facade, which needs a profiled board: see "Finger-jointed robinia decking and cladding – stable and durable". And 20 mm of robinia weighs about 15 kg per square metre, one and a half times as much as Douglas fir of the same thickness.

Key points

· A waney-edge board is edged on one side only: one sawn straight edge, one natural edge. An unedged board keeps both natural edges. Cheaper than finger-jointed cladding and simpler to fix, but rustic in appearance.

· In robinia, waney-edge cladding meets use class 4 (EN 335) without treatment: no biocide in the livestock building.

· Set the overlap from the narrowest board in the batch, about 4 cm, with a single line of stainless steel screws per board per batten.

· Quantity to order: the wall area plus 25 % for overlap and 10 % for offcuts, i.e. about 1.4 m² of boards per m² of wall — or 1 m³ for 33 to 35 m².

· Remove any bark left on the wane before fixing: it comes loose as it dries and holds water.

· This is not architectural cladding: irregular width, lengths limited to 4 m — 2 m sanded with sapwood removed — and longer sorting and fixing.

Frequently asked questions

What is a waney-edge board, and why does it cost less than an edged board?

A waney-edge board is edged on one side only: one edge sawn straight, the other keeping the natural edge of the log, with its rounded wane. An edged board has both edges sawn parallel, which forces the sawyer to cut material off along the whole length, all the more so on robinia, which grows curved. The waney-edge board avoids half of that loss: the yield from the log is much better and the price comes down. Not to be confused with an unedged board, which keeps both natural edges.

Should you remove the bark left on the edge of a waney-edge board?

Yes. Robinia bark comes loose as it dries, holds water behind it and harbours insects: it falls off in patches and leaves a dirty, damp edge. A pass with a drawknife, a scraper or a wire brush on dry wood is enough to remove it before fixing; the debarked edge then greys along with the rest of the wall. Check the condition of the batch when you order: depending on how long it has dried, some of the bark will already have fallen off.

Can waney-edge boards be used to clad a house?

Technically, yes: in robinia, the board meets use class 4 (EN 335) without treatment, on a house as on a barn. Aesthetically, it is another matter: the irregular width and wavy edge give a rustic finish that suits a barn, a cabin or an outbuilding, and a contemporary facade much less. For a house, profiled finger-jointed boards are the right product.

Do livestock damage interior robinia cladding?

Much less than softwood cladding. Robinia is a hard wood, about 50 % harder than oak on the Janka scale, and it withstands rubbing, knocks and gnawing. Tooth marks and rounded corners appear over the years, with no structural consequence on a 20 mm board. The wood as fixed is debarked, and therefore inert.