Backyard ADU Construction in San Gabriel
San Gabriel ADUs and garage conversions that begin with a test hole where the footing will go, then get drawn, filed for city review and built.
A hand auger and a probe rod come out before any sketch on a San Gabriel ADU job. We bore a test hole where the new footing would land and read what comes up: firm native soil, loose fill from an earlier project, buried roots or a damp layer. That reading shapes the foundation and where the unit can sit. We then prepare drawings for the City of San Gabriel to review and build the unit as approved.
What the test hole tells us
Native soil that holds its shape on the auger blade usually supports a standard spread footing. Fill is a different story, since it may have been spread without compaction, and it can settle under a new slab. If we find it, we dig past it to firm ground or bring in a soils engineer to set a deeper design. Tree roots near the hole mean the footing line may need to move or the roots need a barrier. A damp layer points to poor drainage, and we plan a gravel bed and vapor retarder under the slab. You see what came out of the hole before we recommend a layout.
Shell, drainage and city review
Hard sun, dry spells and a heavy rain arriving all at once are what an inland shell has to handle. A pale roof covering cuts heat gain in the rafter bays. Stucco or fiber cement hangs on a wrap that leaves a thin channel for water to run down and out at the base. Each window sits over a sloped sill pan. Downspouts tie into solid pipe that ends away from the footing we sized from the test hole. We answer plan check comments and book each inspection. If the soil calls for a soils report or special footing design, that engineering shows up as a separate figure next to the drawing set.
ADU Construction in San Gabriel: questions
Picture the yard behind your house with every required clearance shaved off: the rear line, both sides and the space kept from the main house. A deep San Gabriel parcel can hold a freestanding cottage in what remains. On a shorter one, an addition-style unit or a converted garage uses the ground better. Soft fill found in one corner can also push the footprint toward firmer soil.
On a San Gabriel lot we put extra care into the structural sheet. Its footing size and depth come straight from what the test hole turned up, and the site plan then places that footing inside the setbacks. Both sheets come in our set, sized for a single-level design holding at most 500 square feet of floor. We prepare it, submit it and carry it through plan check.
Often, and the old slab is where we start. We drill a small hole near an edge to gauge how thick the concrete is and what lies under it, look for cracks and damp, then measure headroom and go over the framing. You get the findings in hand before any recommendation, and a conversion closes the car opening with a framed wall and a window.
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