Cost to Build a House: Cut the Cost of Slab and Roof in Half

    With overall inflation and changes in materials, the cost to build a home is always increasing. Two major cost components in a house are concrete and roofing materials such as shingles. 

    A few years ago after a monster hail storm in Oklahoma City, I remember a conversation with several fellow builders about the cost of shingles doubling in a week. I said, "The solution is simple. Just use half the shingles."

    They thought I was joking, but I wasn't. So how, exactly, do you cut the amount of shingles for a roof in half? The same way you cut the amount of concrete slab in half—you build a two-story home.

    Two-Story Home Cost Savings

    For the same square footage, a two-story house with the second floor completely stacked over the first floor will use half the slab and half the roof as a one-story home. That savings reduces the cost significantly.

    Cost per Square Foot?

    Let's use an example of a 2,500 square foot house with a two-car garage. The garage is about 400 square feet, which means a total of 2,900 square feet within the framed area of the house (ignoring any porches or patios). Divide that in half, and put half on top and half on bottom.

    You just saved 1,450 square feet of slab, which is roughly $13,300 at today's price. You also saved around 1,700 square feet of shingles, underlayment, and roof decking, which would cost about $3,100. That means a total savings of around $16,400. Every house needs a roof and a slab. But by stacking the floors, you pick up another 1,450 square feet for about $8 per square foot cheaper than the first 1,450 square feet you built.”

    One thing to keep in mind with this approach, however, is what rooms go where in the house. If you build a two-story home that's less than about 2,200 square feet, all the bedrooms will have to be upstairs. You need the kitchen, living room, entry, and garage to all fit on the first floor.

    Bedrooms Upstairs?

    After all, it would be pretty hard to use a second-story garage. That means about 650 square feet of living space plus 400 square feet of garage on the first floor. No space left for a bedroom!

    It's a very efficient design if you're okay with all the bedrooms being upstairs, and lots of people build homes that way.

    Energy Efficiency?

    Another great benefit of the stacked two-story design is that the first floor is always in the shade in the summertime—there's no hot attic above it!

    The second floor provides a buffer, which means the first floor air conditioner doesn't have to work as hard and saves you some money.

    The last two houses I've lived in were stacked two-story designs, and the downstairs air conditioner only ran on the hottest days.

    Stacking two stories is a great way to cut the cost of the slab and roof in half. If you're building a custom home, talk to your builder about this and other money-saving design options.

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