How does an ADU in Los Angeles tie into an older main house's utilities?

We start at the main panel and the sewer cleanout. The panel tells us whether the house can share its service or needs an upgrade through LADWP, and a camera run down the lateral shows whether the old clay pipe can accept a new connection. The water supply is checked for size and for galvanized sections that would choke flow to a second kitchen and bath.

Can an old detached garage in Los Angeles become an ADU?

Often, yes. State law lets an existing garage become an ADU within its current footprint, even where it stands nearer a line than new construction could. The catch on an old garage is the floor and the framing. A thin slab with no footing, or sill plates gone soft with rot, can mean heavy repair, and we tell you that before design starts.

How do you make an ADU in Los Angeles match the main house?

The main house's roof pitch, eave depth and siding reveal are the starting point, and the ADU windows are sized to the same proportions. Where the house has wood lap siding, the unit gets a matching lap. Trim widths, rafter tails and paint colors follow. The aim is a unit that looks as though it belongs to the property when seen from the back door.

ADU Construction in Los Angeles

Backyard units and garage conversions in Los Angeles, planned around an older main house, its roof lines, its sewer lateral and its LADWP electric service.

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Rain that runs off a new backyard unit has to go somewhere, and behind an older Los Angeles house the choice of where matters. We pitch the ADU roof to echo the main house, then plan gutters and downspouts that carry water to the street or a planted area, clear of both foundations and the neighbor's fence. The roof comes early in our drawings because it also sets how the unit looks.

Drainage between two buildings

A detached unit can sit 4 feet from a side or rear line, which leaves a narrow strip between its wall and the fence. That strip collects whatever the roof sheds. We grade it away from the new slab, set downspouts into a drain line or onto splash blocks, and keep the discharge off the old house's raised foundation, where standing water can soften the soil under the piers. On a flat yard a shallow swale may be enough. If the lot slopes, the drain path is drawn on the site plan so the LADBS reviewer can follow it.

Power, sewer and the LADWP service

Inside the City of Los Angeles, LADWP supplies the power and LADBS issues the building permit. An older main house may still run on a small panel with cloth-covered wiring behind it, and a unit with a heat pump, an induction range and its own water heater adds real load. We run a load calculation before the design is settled. Sometimes the answer is a subpanel fed from an upgraded main, and sometimes a separate meter suits the lot. The sewer lateral gets a camera inspection as well, since an old clay line can crack where a new branch joins it.

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