Home additions in Naperville, IL

Naperville's three main single family districts set different yards. In R1, lots start at 13,000 square feet and 85 feet wide, the two side yards total 25 feet with at least 10 on each side, and the rear yard is 25 percent of lot depth up to 35 feet. In R1A, lots start at 10,000 square feet and the rear yard caps at 30 feet.

R1B is the tight one. Lots platted before January 27, 1989 can be 6,000 square feet with 6 foot side yards, and the corner side yard is 15 feet instead of 30. Subdivision age matters in R1A too, where older plats get 8 foot side yards and newer ones need 20 feet in total. We pull your plat before we draw anything.

Naperville defines a large room addition as one that grows the house's gross floor area by 50 percent or more. On lots in subdivisions platted before 1989, that triggers the tear down and infill rules. Building coverage is then capped at 35 percent of the lot or 2,280 square feet, whichever is greater, with single story porches excluded and a credit for a detached garage. Roof peaks cap at 40 feet.

Those rules do not apply to one or one and a half story houses, unless the addition goes up. Adding a second floor to a 1980s ranch puts the whole house under the coverage cap. The City also asks applicants for additions of 50 percent or more to email Building Permits about how to submit.

Naperville wants the addition drawn on a full size copy of your registered plat of survey. It must show the electric meter, the electric service line and every basement escape window, because nothing may block the City's electric equipment. Footings go below the 42 inch frost line in the City's code tables, and wood foundations are deleted from the local code.

Bay windows, eaves and chimneys may project 3 feet into most required yards, and decks and patios may run 10 feet into the rear yard. That can buy a few feet of room on a tight lot.

Many Naperville lots have swales in the side and rear yards, with storm features in easements shown on the plat. City code makes it unlawful to change grading in conflict with approved engineering plans. The City's stormwater pages list house additions among the most common causes of new yard drainage problems. We check the swales on your plat and your neighbour's before siting the addition.

In the local historic district, an addition on the street facing facade goes to the Historic Preservation Commission for a Certificate of Appropriateness, and any variance does too. A rear addition out of sight of the street needs no certificate, which is why most additions there go back, not sideways.