Can your house carry a second story?

Los Angeles houses sit on three common kinds of foundation. A raised foundation with cripple walls and a crawl space, common in older houses. A slab on grade, common in post-war tracts. Piers or caissons on a hillside, sometimes mixed with the other two after decades of additions. The drawings on file may say one thing; the house says another.

I expose the foundation where it matters to confirm its type, depth, reinforcement and condition. A new floor needs footings sized for the new load, and the usual answer on an older house is new footings doweled into the old ones, or grade beams that pick up the new posts.

The ceiling joists of a one-story house were sized to hold a ceiling and the attic above it, not a bedroom. Spans, depth and species all matter. The usual answer is a new floor system over or in place of the ceiling joists, with the roof framing above it removed. On a house whose joists were built heavier than they needed to be, some can stay. The evaluation reads them before anyone draws.

Wind and earthquakes push a house sideways, and the walls that resist that push are the shear walls. A second floor raises the house and increases the push, so the engineer designs a continuous load path from the new roof to the footings: shear panels, hold-downs, straps and the posts under them. Where the new shear walls land decides what happens to windows and openings downstairs, which is why this reading comes before the architect fixes the plan.

On a hillside the evaluation includes the soil and the slope, and I bring the geotechnical engineer in early instead of discovering the need at plan check. On a flat lot the question is the bearing under the footings. Either way the soil is part of the load path, and the City reads it as such.

New footings doweled into the existing foundation. Grade beams under new posts. Interior shear walls with hold-downs, which can mean opening a finished wall downstairs and closing it again. New posts and beams where a wall is removed. Piers on a slope. All of it is invisible in the finished house, and all of it is what the engineering is for.

Sometimes the honest answer is a different plan: a partial second story over the wing that can carry it, a ground-floor addition, or an ADU. You get that answer in writing before you pay for a full design set.

The first on-site visit is free. Exposing the foundation where it matters is a scoped step we agree on before anyone digs, and after it you get the structural answer in writing: what the house has, what a second floor would need, and whether a different plan serves you better. The engineer's calculations are a design-stage item, stamped and reviewed by the City during plan check. The full sequence, from this look to the day the roof comes off, is on the second-story additions page, and what the structural work does to the number is on the cost page.