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Update: Remodeling a home is expensive enough as it is, even without factoring in problems that you can’t predict that can drive costs even higher. The best thing you can do to avoid any nasty surprises is to be thorough when calculating costs before you embark on a remodel. Think about materials, labor, building permits and your own expenses – such as eating out if your kitchen is out of use, or staying a couple nights in a hotel if your home is going to be temporarily uninhabitable. As well as working out your maximum costs, you’ll find that you may come across ways to save money too.

Knowing the drivers of home additions cost and working to control them will allow you to contain costs and create the house addition you want or need. Home additions costs are not insignificant. In fact the cost per square foot for an addition can be noticeably more than the cost per square food to build new. The first reason for this is that an addition must be built as an exact match to the existing structure. If your house was not built perfectly level and perfectly square, calculations and adjustments must be made in constructing the addition to achieve a perfect match. A second factor in the additional cost is that some amount of demolition of the existing structure will probably be necessary to connect the addition to the rest of the house. A third factor is repairs that may be necessary to parts of the existing structure that must be torn out to connect the addition. The final home additions cost factor (often not calculated) is working around you and your family, which could involve additional time.

The major elements of home additions cost are:

  1. Preparation and design costs:
    • Architect or designer fees
    • Permits
    • Demolition
    • Site preparation
  2. Construction costs — in each of these cases you will incur materials costs and labor costs:
    • Foundation work
    • Framing
    • Electrical
    • Plumbing
    • Roofing
    • Heating and cooling
    • Cable, satellite, internet, telephone lines and jacks
    • Exterior surfaces
    • Interior surfaces
    • Finish flooring
    • Doors and Windows
    • Cabinets, fixtures, appliances
    • Finish work (trim, baseboards, painting, etc.)
  3. Project management costs:
    • General contractor
    • Subcontractor
    • Inspections
  4. Other costs for the construction:
    • Insurance
    • Losses
    • Repairs
    • Trash disposal fees
    • Cleanup
    • Tools and equipment (for do-it-yourselfers)
    • Safety equipment (for do-it-yourselfers)
    • Sealing off the rest of the house
  5. Hidden costs:
    • Cost of making late changes
    • Upgrades
    • Impact on taxes
    • Impact on insurance
    • Impact on utility bills
    • Decorative enhancements (window treatments, etc.)
    • Unexpected delays or problems
    • Other required upgrades or updates

There are, however, many ways to save money on your addition. With the investment of some time, care, and creative thinking, you can save on most of your preparation, construction and project management costs. Here are a few examples:

  1. Preparation: Instead of commissioning an architect, work with a home designer or a contractor with design skills. Do your own demolition, site preparation, and sealing off of the rest of the house.
  2. Construction: Do as much of the work yourself as possible. Shop extensively and carefully for materials to get the best prices. Use as much pre-fabricated material as possible to reduce labor costs. Think ahead very carefully and frequently about how you will use the space so you don’t end up making changes or adding fixtures late in the process. Remember that any time your contractor or subcontractor must re-do something, you are paying for it twice.
  3. Project management: If you have the time and the contacts, managing the project and acting as the general contractor can save you a large amount of money.
  4. Other Costs and Hidden Costs: Keep upgrades to an absolute minimum. Work smart and work carefully to minimize the need for other repairs. Protect your property and your possessions to prevent losses. Sell or donate as much of what you tear out as possible.

You can find additions cost estimates for your project at And you will find suggestions, design ideas, and resources for your home addition at