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Versatile and essential for countless interior finishing projects, our selection of flat stock offers clean lines and endless possibilities. Also known as S4S (surfaced four sides) lumber, flat stock is ideal for creating custom trim, casings, baseboards, window and door accents, shelving, or modern minimalist moulding. We carry a wide selection of sizes, profiles, and species—including MDF, pine, fir, hemlock, and more—so you can find the perfect material to suit your style and project needs. Whether you're building new or updating an existing space, flat stock provides a simple, refined look that works beautifully in both traditional and contemporary designs. As a proudly Canadian company with locally owned stores, Windsor Plywood offers hard-to-source materials, quality craftsmanship, and expert advice. Visit your local store to browse our full selection of flat stock and find exactly what you need to bring your vision to life.
Frequently Asked Questions
What is flat stock moulding and where is it used?
Flat stock, also called S4S (surfaced four sides), is smooth-planed lumber in standard widths used as trim, casing, panelling components, shelf edging, and general finishing work. It has no decorative profile. The clean, flat face is the design and it is particularly popular in craftsman-style and contemporary interiors.
What wood species are available in flat stock at Windsor Plywood?
Common species include pine, poplar, oak, maple, and MDF in painted grades. Species selection depends on the application. Poplar and pine take paint well and are cost-effective; oak and maple are used where the wood grain will be visible. MDF flat stock is the smoothest option for painted trim.
What sizes does flat stock typically come in?
Flat stock is available in standard nominal widths from 2 inches up to 12 inches and beyond, in various thicknesses. The actual finished dimensions are slightly under the nominal size after planing. Windsor Plywood can confirm available dimensions and lengths for specific project requirements.
Can flat stock be used for craftsman-style casing and trim?
Flat stock is one of the defining materials of craftsman-style trim. Craftsman casing typically uses wide flat stock with a back band detail, and craftsman baseboard uses flat stock with a cap moulding. The result is clean, architectural, and easy to execute compared to heavily profiled traditional trim.
Is flat stock suitable for shelving?
Yes. Wider S4S flat stock in species like maple, oak, or pine is a practical shelving material, particularly for built-in applications and shop shelving. It should be appropriately sized for the span and load. Unsupported spans longer than 24 to 32 inches in 3/4-inch material will sag under significant weight.