Exterior Painting across Waltham, Massachusetts.

A paint job on the outside of a house is mostly preparation. How much depends on the age of the siding, how many coats are already on it, and whether those coats are still bonded. In this city, about 28% of housing units date from 1939 or earlier, and those clapboards may carry a long history of oil and latex layers. Newer siding is a far simpler surface.

The goal on any house is the same: remove what is failing, make the surface sound, prime bare wood, and apply two finish coats in the right weather.

Victorian and earlier houses

The Piety Corner Historic District, around Bacon and Lexington Streets, is described as the city's largest concentration of well-preserved 19th- and early-20th-century houses. Its styles include Federal, Second Empire with mansard roofs, Carpenter Gothic, Queen Anne and Colonial Revival. Each brings its own painting work: the Gothic and Queen Anne houses have brackets, scrollwork and shingles with a lot of edge to scrape and caulk, while a mansard roof puts dormer trim at heights that need staging.

Houses like these often look best in two or three colors, with body, trim and accent picked to separate the details. For the signs that a house is due, see our post on when to repaint a New England house.

Do historic districts limit your color choices?

The city has nine National Register historic districts, listed in 1989 and 1990, including Piety Corner, Lawton Place, Lyman Street and East Main Street. Listing on the National Register does not, by itself, restrict what a private owner does to a house, repainting included, unless federal money or permits are involved.

Waltham does have a delayed-demolition ordinance, but it deals with tearing buildings down, not painting them. If you are unsure whether any local rule applies to your property, a call to the Historical Commission before work starts settles it.

Scraping old paint safely

Some 69% of housing units here were built in 1979 or earlier. On a pre-1978 house, a paid contractor who disturbs more than 20 square feet of exterior paint must follow the federal lead-safe rule, which Massachusetts runs through its own program. A full repaint of an older house will almost always go past that amount.

In practice that means plastic sheeting on the ground under the work, wet scraping, no open-flame burning or high-speed sanding without dust collection, and daily cleanup of chips. It also keeps lead chips out of garden soil and off the neighbor's side of the property line. More detail is on our lead-safe painting page.

• Wash siding and let it dry fully
• Scrape and feather loose paint; replace rotted clapboards or trim
• Prime all bare wood and patches
• Caulk joints, but not the drip gaps under clapboards that let the wall breathe
• Two finish coats, brushed into trim and back-rolled on siding

Two-families and shared schedules

The census counts 2,921 units in two-unit buildings and 3,217 in three- or four-unit buildings. When a building has two owners, as with a two-family converted to condos, the exterior is usually a joint decision: both sides need to agree on color, cost split and timing, and the whole building should be painted at once so the faces match.

One concentration is on the South Side, where census data for one tract shows 61.1% of units in two- to four-unit buildings. In the census tract covering much of Warrendale, by contrast, most units are single-family detached houses, where one owner makes the call.

When to schedule

Exterior paint needs dry wood, temperatures above the product's minimum through the night, and no rain while it sets. That makes late spring through early fall the main window. Our post on the best time of year to paint in Massachusetts goes into the details, and common exterior paint failures explains what happens when those conditions are skipped.