We have been doing a lot of second story addition lately, commonly known as “Pop tops”. I thought it would be good to share a few key things to consider if you are looking at popping the top on your current residence. The most important thing to consider is what lies beneath the surface not above. The second story most be able to find a path for the new load all the way down to the ground.
In Denver a number of the pop top candidates are turn of the century bungalows looking for additional square footage. Unfortunately most of the construction of this time period was load bearing brick walls on pore foundations. These wall types tend to degrade over time and are rarely capable of carrying a second story.
The solution for this is typically to either fur out the interior walls or provide a new “post and beam system” through the house to carry the second floor. Stud walls either 2×4, 16” O.C. or 2×6 24” O.C. tend to hold up better over time and are a much better candidate for reuse to carry a second floor.
Foundations are key as well. It’s not uncommon to dig up an old foundation here in Denver to find just a few inches of crumbling brick sitting on dirt, (I’ve also seen bodark stumps, cmu blocks on dirt, and even a wheel rim, you never know what waits beneath the surface!) These obviously are not good candidates. You’re typically hoping for reinforced concrete going at least 3 foot below grade. If you do not have good foundations or good existing walls, you’ll need to plan on either reinforcing or pouring new ones. This may mean a new footing for interior fur out walls or caissons for post and beam systems.
If you’re considering going “up” have a licensed architect or engineer evaluate your foundations and walls early to make a recommendation. We include both as part of our Needs and Option Review consultations.