La Habra Heights ADU Construction in a Foam-Wrapped Shell
A La Habra Heights ADU wrapped in rigid foam outside the studs to slow heat from hard sun, with a look at the older house's walls and window sills to match.
Rigid foam board, wrapped around the outside of the studs, keeps the heat of hard sun from passing through the walls of a La Habra Heights backyard unit. Insulation fills the spaces between studs, yet each wood stud still carries heat straight across the wall, one small bridge after another. Foam laid over them breaks that path, which keeps the rooms easier to cool and lets a smaller heat pump do the work.
How the wall goes together
The foam goes on over the sheathing with its seams taped, and the water-resistive barrier and flashing are lapped so water drains to the outside face. Siding, or the lath for plaster, fastens through it with longer screws or onto wood strips screwed back to the studs. At each window and door, the frame either sits out in the plane of the foam or gets an extended jamb, and the opening is flashed so its sill sheds water outward. The energy calculations credit the foam, which can reduce the insulation the walls would need between the studs.
The older house's own walls
Walls in an older main house may hold no insulation at all. A small opening behind an outlet cover, or under a lifted course of siding, shows what fills the cavity. If it is empty, cellulose can be blown in from outside through holes drilled in the siding or stucco, then plugged and finished, which leaves the original plaster inside untouched. Any knob-and-tube wiring still live in those walls is checked first, since the electrical code limits burying it in insulation. It is a decision of its own, with its own scope, and the unit's design does not depend on it.
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ADU Construction in La Habra Heights: common questions
With an empty conduit laid beside the power feeder. While the trench is open, a spare pipe with a pull string costs little, and it lets an internet or phone line reach the unit later without digging up the yard. If the parcel relies on a septic tank, the agency that oversees septic systems has to confirm it can serve a second home before design.
Yes, and state law lets a garage converted within its existing walls grow by as much as 150 square feet when the added room serves the entry. That small bump-out can hold a door and a landing, which frees the old garage floor for the main room. When the old siding comes off, those walls can take the same foam wrap as the addition.
Under each window of the main house sits a detail worth copying. Wood windows of that age tend to rest on a projecting sill with a narrow apron board under it, while plastered openings often wrap the plaster into the frame. The unit's windows are finished in the house's way, so the base of each one reads the same from across the yard.
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