Interior Surface Finishing
Interior Surface Finishing tests the sequence, surface tolerance, and product choices that produce a uniform interior film. The exam focuses on drywall finishing levels, primers, cut-in, sheen selection, and the order of ceilings, walls, and trim.
Drywall finish levels and primers
- ASTM C840 and GA-214 describe Levels 1 to 5. Level 4 is common for flat paint under ordinary lighting; Level 5 is specified for gloss, semi-gloss, or critical side lighting because it minimizes joint telegraphing.
- New drywall needs a dedicated drywall primer; skim-coated or repaired areas may need a high-build primer or sealer to equalize porosity.
- Sand, dust, and wipe before priming; glossy patches must be dulled or bonded.
Application sequence
- Ceilings first, then walls, then trim and doors. Cut in with a brush, then roll while the cut-in is wet to avoid a picture-frame edge.
- Maintain a wet edge; back-roll sprayed areas; use the correct nap for texture.
- Caulk cracks and gaps before painting, but use paintable caulk and allow it to cure.
Sheen and durability
- Flat hides defects and suits ceilings and low-traffic walls.
- Eggshell and satin resist cleaning; semi-gloss suits trim, doors, kitchens, and bathrooms.
Worked example
A room is 5.0 m × 4.0 m with a 2.4 m ceiling, two doors at 1.8 m² each, and one window at 1.8 m². Perimeter = 18 m; wall area = 43.2 m². Deduct 5.4 m² of openings = 37.8 m². Ceiling = 20.0 m²; total = 57.8 m². Two coats at 11 m²/L = 10.5 L; add 10% waste = 11.6 L, so buy 12 L.
Traps that cost marks
Specifying Level 4 where Level 5 is required; painting over glossy or dusty patches; failing to caulk before the finish coat; leaving lap marks from dry cut-in; and using a sheen that shows every ridge under critical light.
Key points
- Match drywall finish level to sheen and lighting.
- Prime new drywall and equalize repaired areas.
- Paint ceilings, walls, then trim.
- Keep a wet edge and back-roll sprayed work.
- Choose sheen by durability and defect hiding.