Carpentry Calculators

Flooring and decking layout

Where the first board goes and what is left at the far wall — with both end rows ripped to match when the leftover would otherwise be a sliver. Works for a deck too: give the boards a gap and drop the expansion allowance.

Laying

Decking gets a gap between boards and no expansion gap at the edges

in

= 144"

in

= 180"

in

What it covers

in
in
in

= 0.75"

in
in
End rows

Ripping both keeps the two ends equal

%

For the area estimate

29 rows

First row

5"

Full board

Last row

2 1/2"

Boards

110

Area

180.0 sq ft

By area, plus waste

119

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29 rows · first 5" · last 2 1/2" · joints staggered 12" or more

The first rows, in order

Row 1Start with a 48" piece
5" wide
Row 2Start with a 12" piece — the offcut from the row before
5" wide
Row 3Start with a 24" piece — the offcut from the row before
5" wide
Row 4Start with a 36" piece — the offcut from the row before
5" wide
Row 5Start with a 6" piece
5" wide
Row 6Start with a 18" piece — the offcut from the row before
5" wide
Row 7Start with a 30" piece — the offcut from the row before
5" wide
Row 8Start with a 42" piece — the offcut from the row before
5" wide

21 more rows follow the same pattern: use the offcut from an earlier row when one of them is long enough to clear the stagger, and start a fresh board when none of them is. Boards that are all exactly one length march the joints along in even steps like the drawing above — flooring out of the box comes in mixed lengths, which breaks that up on its own. If yours are uniform, cut a couple of starters at odd lengths.

Before you cut

  • End rows at least 2" wide — passesFirst row 5.00", last row 2.50".
  • End joints at least 6" apart, row to row — passesClosest pair in this plan is 12.0" apart.
  • Expansion gap of at least 1/4" at the walls — passes0.750" at each wall, covered by the baseboard.

What to buy

Boards, from the row planEvery offcut kept and used in a later row where the stagger allows it
110
Boards, by area180.0 sq ft plus 10% waste, at 1.67 sq ft a board
119
Left over at the endBought and not laid. Short ends, mostly — keep the long ones
60"
Row pitchFace width of one board
5"

Measure the room in three places

Rooms are not rectangles. Measure the width at both ends and in the middle, and lay the floor out to the smallest of the three — then the rip on the last row absorbs the difference instead of the last row running out halfway along.

If the far wall is visibly out of parallel, the rip on the last row is tapered, and it is worth scribing that row to the wall rather than ripping it straight. Same board count either way.

About laying a floor

Should I rip the first row of flooring?
If the last row would otherwise come out narrower than about 2", yes. Ripping both end rows to the same width splits the leftover between the two walls, and a 2 3/4" board at each side reads as a deliberate border while a 1/2" sliver at one side reads as a mistake. It costs nothing — the same total width of floor either way.
How big an expansion gap does flooring need?
At least 1/4" at every wall, and 3/8" to 3/4" is normal — check what your flooring maker requires, because ignoring it voids most warranties. The gap is covered by the baseboard or a shoe moulding, so it costs nothing visually. A floor with nowhere to go when it takes up moisture lifts in the middle, and the only fix is pulling the baseboards off and cutting the edges back.
How far apart should end joints be?
Six inches is the usual minimum for laminate and engineered boards; many hardwood installers use eight to twelve. The other half of the rule is not to let joints line up every third row either — a staircase pattern is as obvious as an aligned one. Starting each row with the offcut from the row before produces a random-looking stagger for free, as long as the offcut is long enough to clear the minimum.
How much extra flooring should I order?
Five to ten percent over the room area for a straight layout, fifteen for a diagonal or herringbone one, and more for a room with a lot of doorways and jogs. Order it all at once and from the same batch: flooring is colour-matched by production run, and a box bought two months later will not match the floor it is patching.
Which way should the boards run?
Along the longest wall usually looks best, and for solid hardwood nailed to a subfloor the boards should run perpendicular to the joists — that is a structural requirement, not a preference, and it wins over appearance. Running parallel to the joists needs a second layer of subfloor or a diagonal underlayment first. Decking follows the same rule for the same reason.

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