Interior Painting across Attleboro, Massachusetts.

The city's housing was built over a long stretch of time. Census estimates put the median year built at 1972, with 24.1% of units dating to 1939 or earlier, 37.1% to the years 1940 through 1979, 23.8% to 1980 through 1999, and 15.0% to 2000 or later. Inside, that range means one house may have horsehair plaster and layered oil paint on its window casings while the house next door has taped drywall and factory-primed trim.

The prep for those two rooms is different. Below is how each kind of wall and trim is handled, and where federal lead rules come into the work.

Plaster in the pre-war houses

About one unit in four predates 1940, and many houses from that period have plaster over wood lath. Plaster is hard and quiet, but over a century it develops hairline cracks, loose patches where the keys behind it have broken, and bulges on ceilings. Paint alone does not hold those together.

Loose sections are re-secured to the lath first. Cracks are opened slightly, taped where they keep moving, and filled with a setting-type compound rather than lightweight spackle, which shrinks and telegraphs through the finish. Every patch gets primed before the finish coats, or it will show up as a dull spot under a raking light. On old ceilings a flat finish is the forgiving choice because it hides the transitions between original plaster and repair.

If your house is one of the 19th-century buildings in the Hebronville Mill Historic District, whose National Register period of significance runs from 1850 to 1924, expect the walls and the trim to need this kind of attention before any color goes on.

Lead dust starts indoors

Of the city's 19,121 housing units, 61.2% were built before 1980. The census reports construction by decade, so an exact pre-1978 share is not published, but any house built before 1978 may have lead in its older paint layers. Inside, the risk is dust: sanding a window sill, scraping a stair stringer or planing a sticking door turns those layers into fine particles that settle on floors and get tracked through the house.

The EPA's Renovation, Repair and Painting rule requires certified lead-safe work practices when a paid contractor disturbs more than six square feet of painted surface per room in a pre-1978 home. In practice that means:

• Plastic sheeting sealed over floors and doorways around the work area
• No open-flame burning and no power sanding without a HEPA-filtered shroud
• HEPA vacuuming and wet wiping at the end of each day
• A cleaning verification check before the containment comes down

Drywall and trim from the 1970s and 1980s

The two largest single decades in the census table are the 1980s, at 14.0% of units, and the 1970s, at 13.4%. Walls from those years are drywall, and their usual complaints are nail pops, cracked tape at inside corners and seams that show under new paint. Popped fasteners get reset with a screw beside them, loose tape is cut out and re-run, and the repair is feathered wide so it disappears.

Trim from that era is a mix. Some is stained wood under a clear coat; some was painted with oil-based enamel. Latex will not bond reliably to old oil paint, so a rag with denatured alcohol is rubbed on a hidden spot first: latex softens, oil does not. Oil-painted or varnished trim gets scuff-sanded and a bonding primer. Our finish comparison explains why trim and doors usually take a harder sheen than walls, and the latex vs. oil guide covers the chemistry.

Two-families, small multi-unit buildings and rentals

Buildings with two to four units hold 19.6% of the housing stock, and 33.8% of households rent. If you own one of those buildings, a vacant unit between tenants is the easiest time to paint: no furniture to move, and the whole unit can be done in sequence. Washable eggshell or satin on walls and semi-gloss on trim stand up to move-in and move-out traffic better than flat paint.

For an occupied home, our checklist on preparing for an interior paint job covers what to move and what can stay, and winter interior painting explains how the cold months affect drying and ventilation.