The door casing is the trim that runs around the door opening — the head casing across the top, the side casings down each side. The casing frames the door, covers the gap between the door frame and the wall, and provides the visual transition between the wall and the door.
A PU door casing is a single piece of trim, typically 60 to 150 millimeters wide, with a profile that ranges from a simple flat strip to a developed classical profile. The casing is the same material as the other trim in the room, with the same finish, and it installs with construction adhesive and a few finish nails.
The most common modern casing is a flat strip. A simple rectangle, 60 to 100 millimeters wide, with a flat face and a small chamfer on the edges. The casing is the most restrained option, suitable for modern and minimalist interiors.
A stepped casing is the second most common modern option. A single step on the face, typically 5 to 10 millimeters of additional depth, with a flat or slightly chamfered edge. The casing has a little more presence than a flat strip, but it still reads as modern.
A cove casing is a more traditional option. A small concave curve on the face, typically 10 to 30 millimeters of depth, with a flat or slightly stepped edge. The casing has more presence than a stepped casing, and reads as transitional or traditional.
A molded casing is the most traditional option. A developed classical profile (a cyma curve, a torus, a small fillet) on the face, typically 20 to 50 millimeters of depth, with optional plinth blocks at the base. The casing has the most presence, and reads as traditional or formal.
For sourcing, PU door casings are a stock product at most factories. The casings are sold by the linear meter, in standard lengths (2.4 or 3 meters), and the same profile is available as a complete surround kit (head casing, side casings, corner blocks, plinth blocks). The lead time is short because the casings ship from stock.
A practical install note: the casing is installed after the door and the door frame are in place. The side casings are installed first, plumb on each side of the door. The head casing is installed next, level across the top of the side casings, with a miter or a corner block at each end. The joints are filled with paintable caulk, and the painter's topcoat goes on the next day.
A practical note on the right casing for the right room. The casing's design should be coordinated with the room's other trim — the baseboard, the chair rail, the crown. A modern casing should match a modern baseboard; a traditional casing should match a traditional baseboard. The selection should be deliberate, and the casing should be part of the room's overall composition.
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Frequently Asked Questions
Q: What is polyurethane (PU) decorative material?
A: Polyurethane (PU) decorative material is a high-density closed-cell polymer molded into architectural profiles such as cornices, ceiling medallions, wall panels, columns, and skirting boards. It replicates the appearance of plaster, carved wood, or stone at one-quarter the weight, is fully waterproof, impact-resistant, and arrives factory-primed for paint.
Q: How does PU compare with plaster and wood mouldings?
A: PU is lighter than plaster (no scaffolding required), impact-resistant during transport, and immune to cracking. Compared with wood, PU does not warp, split, or attract termites, and it tolerates moisture in bathrooms and kitchens. The trade-off: PU cannot be refinished the way solid wood can, but its lifespan is 20–30+ years with minimal maintenance.
Q: How do you cut and finish PU mouldings?
A: Cut PU mouldings with a fine-tooth miter saw (40+ teeth for a 10-inch blade) to avoid chipping the molded edge. Sand the cut edge with 220-grit, then apply two coats of interior latex paint. Mitre joints at corners, fill seams with lightweight spackle, sand smooth, and finish with one final top coat.
Q: Is PU moulding safe for indoor air quality?
A: Yes. Premium PU mouldings are manufactured without formaldehyde, asbestos, or VOCs. They meet EN 13501-1 Class E fire classification as a minimum, with Class B fire-retardant versions available for commercial projects. The factory-applied water-based primer further reduces off-gassing once installed.