What is Shiplap?
Shiplap is a type of wooden board with a rabbet (notch) cut into its edges, allowing adjacent boards to overlap and create a tight, weatherproof joint. Originally used for exterior siding and boat building, shiplap has become extremely popular as an interior wall and ceiling treatment, adding rustic charm and architectural character to any space.
Unlike tongue-and-groove paneling, shiplap boards have a visible gap or "reveal" between each board, creating the characteristic shadow line that defines the shiplap look. The boards are typically installed horizontally but can also be oriented vertically or diagonally for different visual effects.
Shiplap Calculation Formula
Common Shiplap Sizes
| Nominal Size | Actual Size | Exposure | Coverage/Board |
|---|---|---|---|
| 1×6 | 3/4" × 5-1/2" | 5" | 3.33 sq ft (8' board) |
| 1×8 | 3/4" × 7-1/4" | 6-3/4" | 4.50 sq ft (8' board) |
| 1×4 | 3/4" × 3-1/2" | 3" | 2.00 sq ft (8' board) |
Installation Tips
- Acclimate boards: Let shiplap acclimate to room temperature and humidity for 48–72 hours before installation to prevent warping and gaps.
- Start from the bottom: Install the first board at the bottom of the wall, ensuring it is perfectly level. All subsequent rows reference this first board.
- Use a spacer: Place a nickel or consistent spacer between boards for uniform reveal lines.
- Nail into studs: Use 18-gauge brad nails or 15-gauge finish nails, driving them into wall studs for secure attachment.
- Stagger joints: If the wall is wider than the board length, stagger end joints by at least 2 feet between adjacent rows.
Worked Example
A 12 ft wide × 8 ft tall wall using 1×6 shiplap with 5.5" exposure and 10% waste:
Rows = (8 × 12) / 5.5 = 17.45 → 18 rows
Boards per row = 12 / 8 = 1.5 → 2 boards
Total = 18 × 2 × 1.10 = 39.6 → 40 boards
Frequently Asked Questions
How much shiplap do I need for a wall?
Calculate the wall area in square feet, divide by the coverage per board (based on exposure width and board length), then add 10% for waste. For a standard 12' × 8' wall using 1×6 boards, you'll need approximately 35–40 boards.
What is the difference between shiplap and tongue and groove?
Shiplap has overlapping rabbeted edges that create a visible gap or channel between boards. Tongue and groove has interlocking edges that fit flush together with no gap. Shiplap is generally easier to install and has a more rustic appearance.
Can I install shiplap over drywall?
Yes, shiplap can be installed directly over drywall. Nail through the drywall into the studs for secure attachment. The drywall provides a flat, stable surface and additional insulation.