This post was inspired by a question from a coworker and ended in something I wish I had known sooner while doing full home rehabs.
As always, this blog is for informational and entertainment purposes only. Before considering any of the ideas here, please consult with the relevant qualified professionals. e.g. general contractor, builder, real estate agent, lawyer etc.
My coworker wanted to know how expensive it would be to build a second story onto her house. To use their own words, her family wasn’t particularly into the idea of moving but they were getting tired of living in a shoe box. I knew this could be done, but didn’t know how economical it was, so I reached out to a few trusted contractors.
In general, building up is actually cheaper. It is easier and less costly to do with older homes based on the way roof construction was done in years gone by. You can lift off the old roof, but in newer homes, you will need to cut through the trusses before raising the roof. There is no significant difference in working on a brick or sided structure, though it first will cost more if you want to raise brick to cover your new story. But if your internal framing is wood then it doesn’t matter.
How far can you build up? A foundation able to hold one story can generally hold two, but for additional stories, you will want an engineer. This is a common rule of thumb; for any specific project, caution is always necessary because you’re making massive structural changes. Your property will be in a state of flux or unlivable, ideally for at least weeks, or potentially for months.
There are both benefits and costs impacting taxes and insurance. Depending on local taxing bodies, often increasing a home’s footprint will increase the assessed value. But when it comes to taxing livable vs non-livable spaces, more research is needed. For insurance, this could be a great time to remediate any old unsafe wiring or plumbing. For ceilings, the cost of rewiring can be especially tricky. An opportunity to do it all at once might be offset by lower insurance rates in the long run.
Anecdotal comparisons in early 2026 within western PA show that building up could cost in the area of $100/sq ft, compared to $150-$200/sq ft for prefab and for brick build, where the costs can go $250/sq ft or higher. The next time I get the chance to work rehab on a home, or house with single floor areas, I may consider this option for setting up a duplex or expanding the living space while improving an aging roof.
Let me know if there’s interest in a post on converting single family homes to duplexes or vice versa. It is a practice seen a lot locally and I do have some experience on it, but not sure how relevant it is in other parts of the country.
Thanks all and have a great day!