ADU Construction in Walnut, Planned From the Grade Up
Walnut ADUs set out from grade readings taken on the first visit, so the floor height, footings and kitchen drain all follow how the yard sheds water.
A laser level goes up in the backyard before a single sketch on a Walnut lot. We shoot readings from the back door of the house to the far fence, which shows how water moves across the yard and whether a pad for the cottage can sit level without fill. Those figures set the floor height of the unit, the depth of its footings and the path its kitchen drain takes toward the sewer.
What the grade readings change
Ground that tips toward the house means the cottage pad is raised a little and a swale is cut to steer runoff around both buildings. Ground tipping away lets the unit sit lower, with a doorway that meets the patio without a step. Where the readings show real fall, a soils engineer is brought in before the foundation is drawn, and the footings can step to follow the ground. Every reading is plotted on the site drawing, so the reviewer sees the same contours we measured and the drainage arrows match the yard.
Kitchen drain and floor height
Each fixture in the unit drains by gravity, and the kitchen sink can end up farthest from the tie-in unless the plan says otherwise. Setting the floor at the right height keeps a steady fall to the house lateral without lifting the cottage onto tall stem walls. We put the sink and dishwasher on the wall facing the connection, run the bath into the same line and leave the bedroom on the far side, where no pipe has to cross. That arrangement also keeps the trench through the yard short.
ADU Construction in Walnut: questions to settle first
On a level Walnut pad with ordinary setbacks, a single wall carries the sink, a freestanding range, the fridge and a dishwasher, plus a small corner of extra counter. If the grade forces a smaller footprint, a compact range and a counter-depth fridge keep the room working. We confirm the shape once the grade readings are on paper.
Reviewers in Walnut want grading and drainage made obvious, so our site plan carries spot grades, the swale and the point where each downspout lets go. Next to it, the floor plan maps the kitchen and bath. We prepare the remaining sheets, submit the package to the city and handle each round of comments until approval.
Sink, shower and toilet empty toward the house lateral through a new wye, at a depth the grade readings let us plan ahead. Domestic water travels out on a valved branch. When the existing panel has spare capacity, a feeder powers the kitchen through a subpanel, and a second meter covers the case where it has none.
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More work we plan in Walnut
Start your adu construction plan in Walnut
Describe the space and the change you want. We reply with what the first visit covers.