Estimating Costs for Second-Story Additions

a house in construction

When you're planning your remodel, you'll need to know about estimating costs for your second-story additions. Many factors go into the planning. If you keep your budget in mind, the project and decisions will proceed more smoothly. As with any remodel, you will probably encounter surprises and you'll want to account for them. This guide will help you estimate your costs and start the planning process.

In general, the least expensive way to construct second-story additions is to build over an existing garage. The walls are easier to reinforce. You can also pour the footings more easily because you don't have to remove flooring. If your plans involve adding above the existing house, the costs will be more excessive and the work will be more invasive.

Consider the following items when you prepare your budget:


Some second-story additions are extensive enough that the homeowners have to move out during the construction process. If you suspect this might be the case for you, you'll need to budget for rent during the project. On the upside, the remodel will proceed more quickly if you're not living in the house. Anticipate the work taking longer than you expect and try to get a month-to-month lease, so that you don't end up owing for months that you don't need the rental.


Unless you have a draftsman and a good idea of exactly what you want, you'll need an architect. The cost will be dependent on the size of the project.

Structural Engineer

In addition to the architect, a structural engineer will be required to sign off on the plans. This ensures that the existing building will be able to withstand the weight of the second-story additions.

Building Permits

Your city building office can help you calculate the cost of the permits. They will be based on the estimated value of the addition. Also keep in mind that your remodel may require you to pay additional school taxes or reassessed property taxes.


You will have to remove and store everything that is in the construction area. If you don't have spare room in other areas of your home, you will probably need to rent storage. This cost can add up quickly. Shop around for a unit that is affordable and flexible with their contract. Since construction lengths are hard to estimate, you won't want to get stuck in a contract that's longer than you need.

General Contractor

If you are planning to hire a general contractor, plan to spend about 30 percent more than you would if you contracted the work out yourself. This is a controllable cost if you can find the proper set of tradesmen.

First-Floor Repairs

If walls need to be opened and footings poured in your existing home, you'll need to budget for the cost to repair them. Keep in mind that you may have flooring that isn't easy to replace and you could be opening a can of worms.

Loss of Laundry or Kitchen

If you lose the use of your laundry room or kitchen during the remodel, you'll have to budget for eating out and laundry costs.

Interior Finishes

The building of the second story will cost anywhere from $100-$500 per square foot, depending on the finishes and materials you use. Keep your neighborhood in mind and don't overspend.


Once you've considered all the costs, add an additional 20 to 30 percent for unexpected expenses. That should have you well on your way to budgeting for your new second-story additions.