In an earthquake, your house should move as one piece.

Older raised foundation homes tend to fail in earthquakes at the same three connections, because for decades those connections were not required to exist. The sill plate, the wood member that the whole house frame rests on, often sits on the concrete stem wall held by gravity alone, so the house can slide off its foundation. The cripple walls, the short stud walls between foundation and floor, stand unbraced, so they can fold sideways like a card table with the house on top. And the posts in the crawl space rest on their pads by weight alone, so shaking can walk them off their footings.

All three failures are preventable with hardware, which is what makes retrofitting unusual among structural work: the vulnerability is specific, the fix is known, and the work happens out of sight in the crawl space without changing how the house looks or lives.

A retrofit is only as strong as the wood the hardware fastens to, and crawl space wood has often spent decades near moisture. Bolting a sill that rot has softened, or bracing cripple studs that moisture weakened, buys hardware and not strength. So the evaluation checks the condition of every member the retrofit will load: sill, cripple studs, posts, and the girders above them, along with the moisture conditions that decide whether today's sound wood stays that way.

Where damage turns up, structural repair comes first and the retrofit fastens to sound material. Where moisture is active, the drainage correction joins the scope, because hardware corrodes in the same dampness that rots wood. The sequencing costs a little patience and buys a retrofit that means something.

Retrofitting ties the load path together so the house moves as one piece instead of coming apart at its connections. That is the honest claim: bolted sills keep the house on its foundation, braced cripple walls resist racking, and tied posts stay on their pads. It is prevention of the most common and most preventable forms of earthquake damage in raised homes, documented with photographs when the work is done.

It is not a guarantee against all earthquake damage, and nobody honest sells it as one. It is also not urgent in the scheduling sense right up until it is unbuyable in hindsight. If you do not know what connects your home to its foundation, the evaluation answers that question for free, in writing, and the answer is sometimes that a previous owner already did the work.