Installed coverage, board shapes, and stock

Shiplap Calculator

Enter installed coverage separately from physical board width. Compare direction and starting edge, then inspect the remaining shapes around windows and doors.

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Add another finish layer

Use this when installing both finishes together on these walls. Each layer has its own selected plan and contributes pieces to the project.

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Measure your wall

Wall width

From the measured left edge to the right edge.

Measured wall height

Board direction

Starting edge

Actual board face width

Effective installed coverage

Measure the installed advance per board, excluding the hidden overlap.

Board lengths & permitted seams

Enter locations verified for your product and its fixing requirements. The planner selects only from these positions after stock lengths, kerf and end trims are set in Materials.

Permitted seams from wall left (in)

One absolute position per line. Empty means no seams. Locations are kept separately for each wall and laying direction.

Shiplap · Plan A · Selected

See your wall, measured to fit.

Enter the wall measurements and the layout settings for this style. Your plan will appear here as you work.

Finished pieces

Complete the measurements to see the finished pieces.

Materials & stock

Only selected plans enter the shopping list. Different profiles keep separate stock, even when their dimensions match.

Project reserve

Project stock estimate

Updating the selected project’s materials…

Shared and existing physical pieces

Sharing requires the same surface, material, geometry and end cuts. Equal lengths alone do not combine pieces. Confirm that the two roles describe one physical component.

No additional matching pairs in the selected plans. Assign matching profiles and confirm a shared floor datum where appropriate.

Count the installed repeat across the wall

Installed coverage is the distance a joined board advances across the wall. Physical board width can include hidden overlap. Measure a joined sample or use the selected product’s coverage dimension; do not substitute the nominal product name.

Horizontal courses repeat over wall height and vertical columns repeat over wall width. This determines the number of bands, not yet the number of stock boards to buy.

Horizontal courses

ceil(wall height ÷ installed coverage)

Vertical columns

ceil(wall width ÷ installed coverage)

Worked layout

Horizontal shiplap coverage

Use my measurements

Courses advance by 5½ inches of installed coverage from the starting edge. The 6-inch physical board face includes the overlap. Each uninterrupted run needs sufficient usable stock or a separately planned seam.

Example measurements

Wall: 120 × 96 in
Actual board face: 6 in
Installed coverage: 5½ in
Starting edge: Bottom

Layout result

Orientation: horizontal
Courses: 18
Final visible face: 2 1/2 in

Compare on the same wall

Only the named layout setting changes. Wall measurements stay the same.

horizontal courses

5 1/2 in installed coverage · 18 pieces on Wall A

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vertical courses

5 1/2 in installed coverage · 22 pieces on Wall A

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Choose the start and read both finishing edges

Measure the intended wall face between its actual stops. Choose the bottom or left start, the opposite start, or balanced first and last boards. Inspect the partial visible faces beside the ceiling, baseboard, corner, and casing.

A narrow visible strip still needs a suitable blank and joining edge. Check how the proposed rip affects the selected product’s engagement and attachment detail. Keep absolute course checkpoints so repeated rounded widths do not accumulate across the wall.

Keep coverage beside and beneath a window

Enter the opening’s finished boundary and any intentional clearance from wall zero. If a course crosses only part of the opening height, it may need a notch while retaining material beside the window. Removing the entire band would leave part of the wall uncovered.

The drawing shows the remaining region and the piece list identifies the manufacturing blank. Net visible area, blank size, and purchased stock are different quantities. Inspect the head and sill pieces before estimating material by area alone.

Resolve long runs before reading a purchase total

Compare each required blank with actual usable stock after end trim and kerf. An eight-foot raw board is not automatically enough for an eight-foot finished run. A shorter board also cannot supply a longer run merely because the total footage is sufficient.

Use longer stock where needed or resolve a deliberate seam arrangement with the selected product’s supported joint locations. An unresolved seam or unsupported fixing position remains a planning condition, not permission to split a board arbitrarily. Add spare material separately from cutting losses.

Follow the chosen product at the wall

Coverage geometry does not specify hidden fastening, backing, product movement gaps, or an exterior siding system. Confirm the manufacturer’s orientation, edge-cut, and joint instructions for the actual board.

If the stock or cut schedule is incomplete, use the visible coverage and blank demand as a layout check while resolving those inputs. Do not treat a clean elevation as proof that every board can be cut and attached as shown.