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How To Decide When To Add a Second Story


Q: “We are about to have a third child and need more space. We are trying to decide whether we should add a second story to our ranch-style home, or just add another bedroom and bath on the first floor. Could you explain the factors in deciding to go up versus adding on to a single story house?”

A: In the most simple of scenarios, a single story addition to your home should cost less and be easier to build than adding a second story. However, a second story addition will save yard area for outdoor activities. And if your single story home already maximizes your lot, your only option for more space would be to add up (or down, but that will be in another post).

The first thing to consider is the zoning for your area. It is important to know what your property is zoned to know whether you are allowed to build an addition outside of the existing footprint of your house. The setbacks and zoning vary from one City to another, so check with your local planning department for the specific regulations for your property A setback is the minimum allowable distance from the property line to any structure. If your home is already on these setbacks, you cannot put additional square footage on the ground level.

Some cities in the Bay Area require a special review if you plan to do a second story addition. This is another important item to ask your local Planning Department. For example, in the City of San Jose, a second story addition does not require an overly involved planning review. However, many single story additions may qualify for an express plan check, which could save you up to one month in your schedule. In like Palo Alto, expect to have the total square footage of the home reduced if you want to build up. In Sunnyvale, the floor area of the second floor must be smaller than the first floor and the second story setbacks are much larger than those for a single story. And in Los Gatos, a second story requires a design review , sun path diagrams, neighborhood drawings and neighborhood notification.

Before you begin designing your second story, look at the floor plan of your original house to see if you need to add new a new hall way or if the path to the addition makes sense in the overall flow of the house. Adding a new bedroom addition off of the existing hallway or near other bedrooms put the new bedroom close to other bedrooms and will help to conceal that an addition was ever made. But, for example, if there is nowhere to go except through a laundry room to get to the new bedroom or behind a kitchen, it then becomes obvious that a modification occurred.

Another important issue is that you must not remove windows from an original room without replacing those windows with new ones. I’ve seen many additions that have left kitchens in the dark, or bedrooms without any means of escape (if there’s a fire). Always keep in mind that you need natural light and ventilation for all rooms (bathrooms and utility rooms are exempt from needing natural light).

A second story addition will often cost more than a single story addition of the same square footage. That’s because most single story homes do not have an adequate foundation to carry the burden of another story. So, it is likely that the home’s foundation will have to have extra support added to it. This could also mean opening some of the existing floors and walls to add the extra support.

Connectors called “holdowns” and shear walls may also have to be added to strengthen the whole building to meet with current earthquake codes. You may also have to hire an architect or engineer to specify the proper connectors and provide the City with calculations. The structural modifications will add tot he cost of the project, but in the long run you will have a safer home designed to remain standing after a good ground shake.

Lastly, always get a building permit for any addition that you do for your home. This protects you from poor construction that may put your family’s safety in jeopardy. It will also allow you the best possible return on your investment when you later decide to sell your home and move.



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