Thursday, June 30, 2011

Second Story House Additions

I am frequently approached by clients who need more living space and during the initial conversation toss out the possibility of doing a second story addition.  Having done two second story additions for myself, acting as architect, owner, and general contractor, I feel that I have some unique perspectives on this issue.   
To determine whether a second story is feasible or not you need to look at all of the impacts of constructing a second story as opposed to ground story.  Applying a simple cost per square foot for the new construction will not work here.  The ground floor will need to be upgraded to carry the upper floor loads, both gravity loads and seismic loads.  Invariably some of the footings will need to be enlarged to carry the upper floor loads.  The method for doing this is called underpinning.  It is accomplished by digging under the existing concrete footings and increasing the effective size by pouring a new larger footing under the existing footing.  If the house has a slab floor this can be trickier as often some interior footings are required within the interior portion of the house as well as the perimeter.  

The other thing that needs to be considered is the location of the stairs that will be required to connect the two floors.  Stairs can take up almost as much ground floor space as a small bedroom.  So, while you are adding space upstairs you may be subtracting 100 square feet or so from the ground floor.  Also the location of those stairs is critical to a functional circulation pattern on both floors. There are some other drivers of additional costs like marrying the roof forms together and likely the necessary cost of doing some of the construction work from scaffolding.   

However, the most important thing to consider is how much the ground floor is being impacted.  It is easy to underestimate.  For instance if you move a wall between two rooms you will need to patch the ceiling, trim, and floor finishes in two rooms, as well as paint and add electrical in the wall.  And, if you are relocating the kitchen and remodeling a downstairs bathroom, as well as adding the stairs, plus new footings, you will be quickly approaching the cost of a tear down and rebuild.   

So my best advice is this: if you can accomplish your goals with an extension on the ground floor, it will cost considerably less than a second story addition.  If your situation will not allow for this, and you are required to go to a second story configuration, go into it with realistic expectations, and anticipate moving out for a period of time.  You can check out my second story remodel on my website:  
We actually lived on the property except for three nights when the plumbing was out of service.  The construction time was 15 months.  

If after reading this you have questions and feel that I can help, please don’t hesitate to contact me.  I’m happy to answer questions informally.