Altadena ADU Construction, Starting With What Still Stands
Altadena ADU construction on a cleared lot: a standing chimney measured and made safe first, county plan check, old remnants removed and an inspected build.
If a chimney still stands on a cleared Altadena lot, it is the first thing we measure. A masonry chimney left alone after a fire can lean, crack at its base or lose mortar to the heat, and it may sit close to where the ADU would go. We check its plumb with a level, look at the joints and the base, and mark a fall zone around it, so no one works inside that circle until it is braced or taken down.
What the county asks for
Altadena's ADU permits come from Los Angeles County Public Works, since the community is unincorporated. Taking down a chimney or other remnant can need its own county permit, and the site plan for the unit shows where the old house, its chimney and any surviving walls stood. Altadena parcels can carry a fire hazard severity rating, and on a rated lot the drawings follow the wildfire rules for roof, vents, siding and glazing. The fire department may look at access and water supply as well. If the lot slopes, a grading and drainage plan can join the set.
From cleared ground to a finished unit
Once the chimney is down, its footing is broken out, because a block of old concrete under a new slab settles differently from the soil around it. The hole is backfilled in lifts and compacted, and the soils engineer may test it before the unit's footing is formed. Old pipes that served the house are found, capped or reused after testing. The build then follows the county's inspection card, which lists footing, slab, framing, roof, rough trades, insulation and final, and each entry on that card is signed before work moves on.
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When both sets of plans are on file with the county, the unit can lead. Building it first puts a finished small home on the lot while the main house drawings are reviewed, and the services we reconnect for it are sized so the house can join them. Moving in early follows the county's occupancy rules.
For an Altadena parcel, the site plan shows where the old house and its chimney stood and where the unit sits in relation to them. The package covers that sheet for a single-level unit capped at 500 square feet, once we check the parcel ahead of any contract. Breaking out an old chimney footing is priced apart from the package.
If smoke reached a surviving garage, cleanup comes before any conversion. Drywall, insulation and other porous materials that hold odor are removed, and the framing is cleaned and sealed. Heat damage is a separate check, since charred studs or a spalled slab may need replacing. With both answered, converting the garage is priced alongside building a new unit.
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