One wall shared,
a second home grown off your Carmichael house.

Your shared wall stops being an ordinary interior wall the moment two separate dwellings sit on either side of it. Code wants a rated separation. Usually that means a one-hour fire assembly running floor to roof — the right gypsum layers, fireblocking at every penetration, and a sound-rated cavity so your tenant isn't living inside your TV. This is the part that surprises people. Carmichael is a mid-century area, and on a 1958 ranch we've opened a wall expecting clean framing and found cloth-wrapped wiring and board sheathing that won't carry the rating as-is. We draw the assembly on the plans, build it to the listed spec, and the County inspector signs off on a wall that physically exists — not a note in the corner nobody honored.

The reason an attached ADU usually pencils cheaper than a detached one is right there in the name. You tap the slab, the SMUD service and the water line already running to your house, instead of trenching across a quarter-acre Carmichael parcel to a freestanding cottage. One honest caveat: at 750 sq ft the County can require a separate water meter, and on some lots SMUD wants a panel upgrade before adding a second kitchen's load — so we size the unit knowing where that line sits. An attached unit also fits a tighter side yard than a detached build needs, which helps on the few Carmichael lots that aren't generous. We've landed attached projects around $247K where shared utilities did the heavy lifting.