Exterior Painting right here in Dorchester, Massachusetts.

The City of Boston's open space plan describes Dorchester's housing in one line: one- to four-unit frame housing predominates. Current Census estimates bear out the unit-count part of that. Across the four ZIP codes that cover most of the neighborhood (02121, 02122, 02124 and 02125), 55.6% of housing units sit in two- to four-unit buildings, and 52.9% of all units were built in 1939 or earlier.

For exterior work, that points to a lot of old wood-frame houses whose clapboard and trim, where not covered by later siding, carry many coats of paint. On a three-story building, the upper floors are reached by staging or long ladders rather than from the sidewalk. The condition of the wood under all those coats, more than the color on top, decides how long the next paint job lasts.

Triple-deckers, Victorians and what their siding needs

According to the Boston Preservation Alliance, nearly all of the city's older triple-deckers are wood-frame. Queen Anne examples from the 1880s to about 1900 used decorative shingles alongside clapboards, and Colonial Revival examples from the mid-1890s into the 1920s introduced two-story front porches. Dorchester's versions mix the flat roofs common in South Boston with the pitched roofs found in Roxbury.

Each of those details changes the prep. Fish-scale and other cut shingles have many edges to scrape and prime, and a lot of surface per square foot. Cornices and eaves hold water wherever gutters back up, which makes them a common spot for paint to let go. Stacked porches mean columns, rails, balusters and ceilings on two or three levels. Older houses on Savin Hill and Jones Hill, built as one- and two-family Victorians, add trim profiles that have to be scraped by hand.

• Scraping and sanding failed paint down to sound edges
• Spot-priming bare wood and replacing glazing or caulk where it has failed
• Repainting clapboard, shingle, trim, porches and porch ceilings
• Calling out rotted boards or sills for carpentry before paint goes on

Lead paint on the outside of older houses

Across those four ZIP codes, 76.1% of housing units were built in 1979 or earlier. The Census groups the 1970s together, so it can't isolate 1978, the year residential lead paint was banned, and on a house from the 1930s or earlier, the older layers under the newer paint should be treated as lead-containing unless a test shows otherwise.

Exterior scraping on those houses is regulated by the EPA's Renovation, Repair and Painting rule: certified renovators, plastic sheeting on the ground, containment of chips, and no open-flame burning or uncontained power sanding. On a lot where the next house is a few feet away, keeping debris out of a neighbor's yard is part of the job. The lead-safe painting page covers the method. The City of Boston's Lead Safe Boston program also offers free lead inspections and forgivable loans for lead removal in one- to four-family homes, subject to its eligibility rules.

Bay and river exposure

Dorchester's eastern edge runs along Dorchester Bay to the mouth of the Neponset River, and the river forms its southern edge. Houses facing open water or the beaches at Savin Hill and Malibu can take more wind-driven rain and sun on the exposed elevations than a house on an inland side street. On any building, the south and west walls and the water-facing side are the first places to check for chalking, cracking and bare wood.

Historic districts and design review

Dorchester has a long list of National Register historic districts, including Savin Hill, Harrison Square in Clam Point, Codman Square, Lower Mills and several districts along Columbia Road, Intervale Street and Uphams Corner. National Register listing is an honor and a record; on its own it does not create local design review.

None of the ten local historic or architectural conservation districts administered through the Boston Landmarks Commission is in Dorchester. That means repainting a house in a Dorchester National Register district does not, by that listing alone, require a Landmarks Commission approval for color. If a property has any other designation, it is worth checking with the city before choosing new colors.

Planning the season

Exterior paint needs dry wood and temperatures within the product's label range through the drying period, so the practical window in Massachusetts is late spring into fall. For the late end of the year, see painting a house exterior in November; for why paint lets go on New England siding, see common exterior paint failures. If the inside needs work too, the interior painting page for Dorchester and the deck and porch staining page cover those jobs.