Whether its Atherton or any town along the Peninsula, it's always easier to remodel a home without changing the footprint of the building as compared with building a brand new home. In remodeling a home, the owner will certainly need to upgrade the electrical and the plumbing and some portions of the structure, but this type of job seldom requires the same level of expertise or studies as would a home. Most new home projects require soils engineering reports, structure engineering reports, architectural reports, designers--not to mention all of the people/trades required to complete the home. Unless you've personally overseen such large scale construction, you might find the job of building a home from scratch to be a bit more complicated than you could imagine.
On the other hand, a remodel of existing property, usually requires far less studies (usually architect and decorator) and the trades involved in the interior work. You'll also find far less of personal and financial investment required for a remodel.
The procedures for obtaining building permits is the same in all towns and cities in Caifornia. Population density plays a big part in the ease of meeting with a planner to get approvals. In Atherton, the procedure is simple but the City values its community architecture and aesthetics, so a home that differs drastically in appearance from those along an established street might have a harder time obtaining approval from the planner than one that "blends" into the existing street scape and architecture.
Good luck. For more information about planning in Atherton, talk with their City Planning and Building Department representatives.
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