Square-edge lumber is the most versatile profile in the catalog. With flat, smooth faces and crisp 90-degree edges, it serves as the foundation for trim, shelving, furniture, fencing, and any application where boards are installed without an interlocking joint.
S4S – Surfaced Four Sides
S4S is the most common surfacing designation. All four faces of the board—both flat faces and both edges—are planed smooth by the mill. The result is a board with consistent thickness and width, ready for finish work. S4S lumber is the standard for interior trim, baseboard, casing, shelving, and painted or stained applications where a smooth, uniform surface is required.
When you order a "1x6 S4S," you receive a board that measures 3/4" thick by 5-1/2" wide—the actual dimension after surfacing from the nominal 1" x 6" rough size.
E4E – Eased Four Edges
E4E takes an S4S board one step further by rounding the four long edges with a slight radius (typically 1/16" to 1/8"). This "easing" removes the sharp arris that can splinter or cause discomfort on handrails, deck boards, and furniture edges. E4E is the standard profile for tropical hardwood decking boards sold in square-edge (non-grooved) configuration. It is also commonly used for fence pickets and exterior trim where a softer edge is preferred.
S1S2E – Surfaced One Side, Two Edges
S1S2E lumber is surfaced on one flat face and both edges, leaving the back face rough-sawn. This is the primary, indispensable material for authentic exterior Board & Batten and Reverse Board & Batten siding. The rough-sawn face is mechanically superior for exterior applications because the textured surface holds stains and paints significantly better than a smooth planed face, extending the lifespan of the finish. S1S2E costs less than full S4S because it requires fewer planer passes, and the rough back improves performance by allowing moisture to escape more evenly.
Board & Batten estimating ratio: one 1x12 board requires exactly one 1x4 batten (1:1). This precise ratio formula simplifies the estimating process and prevents over-ordering battens or under-ordering primary wide boards.
Dimensions Reference
| Nominal | Actual (S4S) | Common Uses |
|---|---|---|
| 1x2 | 3/4" x 1-1/2" | Battens, lattice strips, edge banding |
| 1x3 | 3/4" x 2-1/2" | Battens, screen molding, light trim |
| 1x4 | 3/4" x 3-1/2" | Trim, casing, baseboard, shelving |
| 1x6 | 3/4" x 5-1/2" | Trim, fencing, shelving, paneling |
| 1x8 | 3/4" x 7-1/4" | Board siding, shelving, furniture |
| 1x10 | 3/4" x 9-1/4" | Board & batten siding, wide shelving |
| 1x12 | 3/4" x 11-1/4" | Wide shelving, furniture panels |
| 5/4x6 | 1" x 5-1/2" | Decking, stair treads, heavy trim |
Species Availability
We stock S4S and E4E square-edge boards in Eastern White Pine, Western Red Cedar, Cypress, Yellow Pine, Poplar, Red Oak, White Oak, and all tropical hardwood species (Ipe, Cumaru, Garapa). Custom species and non-standard widths are available through our millwork program.
When to Choose Square Edge
Choose square-edge lumber when boards will be installed with visible gaps (like deck boards with spacers), butted together without a mechanical joint (like board-and-batten siding — use S1S2E with a 1:1 board-to-batten ratio), or used individually (like trim and shelving). S4S is also required for all deck stair treads and perimeter boards. If you need boards to interlock for a weather-tight or seamless surface, look at our tongue-and-groove or overlap siding profiles instead.
Available Products
Don't see your size or profile? Request a quote and tell us the species and specs you need.
Eastern White Pine 1x8
Eastern White Pine 1x10
Eastern White Pine 1x12
Eastern White Pine 1x6
Ipe 5/4x6
Eastern White Pine 1x4
Ipe 1x4
Cumaru 1x6
Garapa 1x6
Ipe 1x6
Ipe 2x4
Ipe 2x6