ADU Construction in Westlake Village, Drained at the Bank
Westlake Village ADUs set into a cut, with the upper gutter, a swale on the bank above and the wall drain each piped separately to lower ground.
If a Westlake Village ADU is set into a cut, its upper eave may sit only a short way below the bank behind it, so water off the roof and runoff coming down the hill arrive at the same edge. We design that edge as one drainage line: a gutter sized for the roof, a paved swale along the top of the cut for the hillside, and closed pipe carrying both around the unit to lower ground.
Three kinds of water at the back
Roof water fills the upper gutter, surface water sheets off the bank into the swale, and groundwater seeps toward the retaining wall behind the unit. Each one gets its own path. The gutter drops into downspouts at the ends, the swale empties into an inlet with a grate, and a perforated pipe in gravel behind the wall collects what soaks through. Keeping them apart stops a storm on the bank from overflowing a gutter sized only for the roof. Downhill of the unit, the lines may join in a junction box, and a single pipe leaves for the outlet shown on the grading plan.
Leaves, embers and the gap behind
The strip between the roof edge and the bank collects leaves blowing down the slope, and where the parcel appears on the fire hazard maps, that debris sits right against the building. Metal gutter guards keep the trough clear, the roof carries a Class A rating, and the space behind the unit stays wide enough to walk through with a rake. Plants on the bank above stay low and spaced. The swale is cleaned each season along with the gutters. Plan check for Westlake Village covers the grading and drainage plan along with the building set, and the inspector walks the swale and the outlet before the final.
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ADU Construction in Westlake Village: questions
A Westlake Village unit cut into a slope needs a strip behind it wide enough for the swale, the gutter and a person with a rake. Add the setbacks, a sewer route that falls to the house and soil that bears a footing, and the workable spots narrow quickly. We mark them on the survey.
Yes, when the unit qualifies, stays on one story and holds its floor to 500 square feet or less. For Westlake Village, the grading plan shows the swale, the gutter outlets and the pipe route to lower ground, which the reviewer checks against the cut. Engineering the cut, and building the unit, get their own quote after the lot visit.
The cut itself and the retaining wall it calls for, which is often the largest line. The paved swale, the subdrain behind the wall and the closed pipe carrying everything downhill add trenching. Where the fire maps include the parcel, metal gutter guards join the order.
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