An addition is new construction attached to an old house. It needs its own foundation, framing, roof, exterior finish, insulation and mechanical connections, and then it has to be tied into the existing structure so the two read as one. That is why it is the most expensive way to gain space, and why design and permitting take longer than for any interior remodel.

  • Bedroom, bathroom and primary suite additions
  • Kitchen and family room bump-outs
  • Four-season rooms and enclosed porches
  • Garage additions and rooms over a garage
  • Second-story additions where the lot will not allow building out

What an addition costs

HomeAdvisor reports an average of about $51,018, with most additions between $21,902 and $83,358. By area, building out typically runs $80 to $210 per square foot. Building up costs considerably more per square foot, because the existing structure has to be reinforced and the roof removed and rebuilt. Rooms with plumbing — a bathroom, a kitchen — cost more per square foot than a bedroom or family room.

What has to be settled before design

Start with what the lot allows. Zoning sets how close a structure may come to each property line and how much of the lot may be covered, and easements can rule out part of the yard. Check these with the city's planning office before paying for drawings.

Next comes the foundation. Footings must extend below the frost line, which is deep in eastern South Dakota, so even a small addition involves real excavation. Then the systems: whether the existing furnace, air conditioner and electrical panel can serve the added space or need upgrading.

Add on or move?

Compare the full cost of the addition with the full cost of moving — selling costs, a higher purchase price and, for many owners, giving up a mortgage rate they could not get again. An addition makes most sense when you like the location, the lot has room, and the finished house will not be far above the value of its neighbors.

Common home additions situations in Sioux Falls

  • A house that fits the lot and the neighborhood but not the family
  • No bedroom or full bath on the main floor
  • A kitchen too small to remodel within its walls
  • A parent moving in who needs separate space
  • A three-season porch that is unusable half the year

Home Additions FAQs

How long does a home addition take?

Allow two to three months for design, bids and permits, then three to six months of construction for a typical single-story addition. A second story takes longer. In this climate, starting excavation in spring or summer avoids pouring footings into frozen ground.

Is it cheaper to build out or build up?

Building out is usually cheaper per square foot, provided the lot has room within the zoning setbacks. Building up avoids new foundation work but requires strengthening the house below and replacing the roof, and the family often has to move out during construction.

This content is reviewed by the Sioux Falls SD Home Remodeling editorial team and informed by licensed-contractor sourcing, manufacturer documentation, and established industry standards for Home Remodeling. Read our editorial standards.