The most difficult type of construction project you could ever do is to add another story to a house. Upper floor additions are challenging to construct and very expensive to build.
After you demo the existing roof, you typically need to tear apart the lower floor walls to access the plumbing, electrical, and the structural components which must be reinforced and updated. The walls in existing homes are commonly not compliant with the earthquake requirements since they do not have plywood on the exterior (which helps to brace the entire building when the earth shakes and also when wind blows against it). Plywood needs to be added to either the interior or exterior of walls, so this requires either removing the drywall or siding, respectively (and putting it back together when you’re done). You also commonly need to upgrade the insulation, plumbing, and electrical while the walls are opened up.
The foundation of an existing house was also originally built to hold up a one story house - not a two-story house. Additionally, the current code requirements are more stringent for foundations, so it is common that you would need to upgrade the existing foundations to comply with the current code requirements to support the extra weight.
Once you have spent all that money to address the structural items inside the existing parts of the building, then you can start spending money to build the upper floor addition. Once that is done, then you will also need to go back and spend some more money to repair all the stuff within the existing house that got torn apart or damaged in the process. In my experience of doing several upper floor additions every year, the construction cost of rebuilding the existing house is usually equal to (or more) than the cost of building the addition. This makes them the most expensive project type you could undertake.
Another thing to consider, adding a stair to provide access to the new upper floor is a major undertaking. Stairs are expensive to build, and they also take up a ton of space. A stair has a minimum 3’x3’ landing at the top and at the bottom. The stair is usually 14’ long (give or take). Add that all up, and you’ll need to find at least a 20’x3’ space within the existing home to fit the stair. This usually means sacrificing an existing bedroom to become a stairway. So, you need to re-gain that lost bedroom in the new addition to be back where you started in terms of bedroom count.
Although upper floor additions are challenging, we know how to do them. Our experience can help you make informed decisions and take as much pain out of the process as possible. You do need to plan to significantly disrupt your existing house though (and probably move out for awhile during the work).
If you’d like to learn more about our design process, visit www.josharch.com/process, and if you’d like to get us started on your project with a feasibility report, please visit www.josharch.com/help