How much extra flooring do I need for herringbone or diagonal laying?
Diagonal laying costs 10-15% wastage and herringbone 15-20%, against 5-10% for straight laying — on 30 m² that's 3-4 m², or roughly two extra packs.
Short answer: Straight laying costs 5-10% wastage, diagonal laying 10-15%, and herringbone or chevron 15-20%. On a 30 m² floor that means ordering roughly 32, 34 and 35.5 m² respectively — about two extra packs for herringbone compared with straight laying. On top of that, herringbone boards themselves are usually more expensive per square metre than ordinary planks in the same timber.
Why the pattern costs you wastage
Wastage in a floor arises in one place: where the pattern meets the wall. In the middle of the room the boards lie as they were made, and there is no waste at all. Along the edges every board has to be cut, and the only question is whether the offcut can be used again somewhere else.
With straight laying it usually can. Cut 40 cm off a board to finish a row, and those 40 cm can start the next row — provided the stagger rule allows it (typically at least 30-50 cm between end joints in neighbouring rows). That's why wastage is low: 5-7% in a rectangular room, 8-10% in a room with lots of corners.
With diagonal laying it can't. Every board is cut at 45° at both ends, and the triangles left over only fit back in if there happens to be a matching angle elsewhere to use them. Some can be reused in the opposite corner — most can't. Wastage lands at 10-15%.
With herringbone and chevron the edge is twice as long, measured in cross-section. The pattern meets all four walls at 45°, so the whole perimeter is cut triangles, and those triangles come in two mirror-image versions. Wastage lands at 15-20%.
The three patterns, and what each one demands
Diagonal laying is ordinary planks laid at 45° to the walls. The pattern is classically used to hide the fact that a room isn't square: when no board runs parallel to any wall, the eye doesn't register that the walls aren't parallel to each other. The price is the wastage — and the fact that the room has to be set out from a diagonal centre line running through the middle, not from a wall.
Herringbone is rectangular boards laid at 90° to one another in an offset, stepped pattern. The boards themselves are identical; it's the laying that creates the pattern. Herringbone is typically glued down rather than floated, because click joints aren't designed to take strain across their width. Length and width have to divide evenly — a herringbone board is often made in a 4:1 or 5:1 ratio precisely so the pattern comes out even.
Chevron is boards that are cut at an angle at the factory, so they meet in an unbroken V-point. They're supplied as left- and right-handed pieces, and the two kinds have to be used in equal numbers. That matters for the wastage sum: you can't just flip an offcut over, and if you run out of one kind, a pack of the other won't help.
The sums, pattern by pattern
Take a 30.00 m² room and a pack that covers 2.22 m².
Straight laying, 7% wastage: 30.00 × 1.07 = 32.10 m². 32.10 ÷ 2.22 = 14.46 → 15 packs = 33.30 m².
Diagonal, 13% wastage: 30.00 × 1.13 = 33.90 m². 33.90 ÷ 2.22 = 15.27 → 16 packs = 35.52 m².
Herringbone, 18% wastage: 30.00 × 1.18 = 35.40 m². 35.40 ÷ 2.22 = 15.95 → 16 packs = 35.52 m². Here it's tight — and exactly the point where you should buy 17, because a 0.12 m² margin is nothing once the first miscut happens.
Chevron, 18% wastage split evenly: 35.40 m² split into 17.70 m² left-handed and 17.70 m² right-handed. If sold in separate 2.22 m² packs: 17.70 ÷ 2.22 = 7.97 → 8 packs of each = 16 packs in total.
What pushes wastage to the high end
- Small rooms. The edge takes up more per square metre in an 8 m² room than in a 40 m² one. Add 2-3 percentage points below about 12 m².
- Out-of-square walls. Every out-of-square wall creates cuts at its own angle, and those can never be reused. Add 2-3 percentage points.
- Lots of penetrations. Radiator pipes, columns, bay windows, a staircase string — each one costs a board.
- Long boards. A 2.20 m board leaves a larger unusable offcut than a 1.20 m board does. Add 2-3 percentage points.
- Directional grain. Boards with a strong grain pattern or a marble look can't freely be flipped 180°, which halves the chance of reusing an offcut.
- A border or frieze board along the wall. A herringbone floor is often finished with one or two frame rows of whole boards. That's extra material and has to be calculated separately: perimeter × board width × number of rows.
The supplier's own guidance always trumps these rules of thumb. Manufacturers of herringbone and chevron flooring often state a specific allowance for their exact product — and some sell sets where the wastage is already built into the stated square metreage.
Setting out: herringbone starts in the middle
A herringbone floor is set out from the room's centre axis, not from a wall. You find the room's centre line, snap a chalk line, and lay the first "fish" symmetrically around it. From there you work outward towards both sides. Do the opposite and start in a corner, and the pattern ends up skewed at the other end of the room — and a half fish in a visible corner can't be fixed afterwards.
That means you need to know the room's precise internal measurements before laying, not partway through. And it means an out-of-square room needs a chosen reference line: either the wall you see first on entering, or the longest wall. The pattern will run parallel to one and skewed against the other — that's a choice, not a mistake, and it has to be made deliberately.
If you have a measured floor plan with the actual wall lengths and the room's real shape, the centre line and reference line can be worked out on the drawing instead of on the floor with a chalk line. HouseSense produces that plan by scanning the room with the iPhone's LiDAR, or by you drawing the room with your finger and entering the measured centimetres. Out-of-square rooms are drawn out of square: that's the whole point when a pattern has to be set out.
In short
The pattern costs you three times over. It costs wastage (5-10 percentage points more than straight laying), it costs material (herringbone and chevron boards are more expensive per m² than ordinary planks), and it costs labour time (a glued herringbone floor takes markedly longer to lay than a floating click floor). But the wastage percentage is the one of the three you can easily forget — and the only one that stops work in the middle of the room if you get it too low.