How to Build Additions: Before You Begin and Project Management


If your home is too small, you have three options: move to a larger home; reorganize your present space; or add new space. Adding on is often less expensive and less disruptive than moving, and it allows greater freedom of design than altering interior space.

This online guide is a manual for constructing your addition once you have a set of plans. It emphasizes how various building stages re late to each other and to the project as a whole, focusing on the little details that are often forgotten.

Whether you plan to build the addition yourself, manage the job while others do the work, or leave it all to general contractors, this guide gives you the head start you need to bring your project to a successful conclusion.

The second-floor addition includes a bedroom with greenhouse window, a bath, a dressing room, a small study, and huge closets. The first floor under the addition was extensively remodeled.


Good working drawings are vital to the success of any addition project. They should be the result of a careful and enjoyable planning process, with input from all members of the household and consultation with at least one design professional.

You will need the drawings to itemize materials, estimate costs, get a loan, obtain permits, negotiate bids, and guide construction. The longer and more thoughtful the planning process, the easier each of these tasks will be. For more information, see our guide, How to Plan and Design Additions.

Determining Your Role

How much of the work will you do yourself? Some homeowners tackle - an entire remodeling project on their own; others hand over the keys to a general contractor and expect the job to be finished when they return from vacation. You are probably somewhere in between: You plan to do some of the work yourself or per haps act as the general contractor and manage the job.

The following guidelines will help you determine your role by assessing your own skills and enthusiasm.

Doing the Work Yourself

After reading this guide you will have a good idea of what skills, tools, and experience are required for each stage of your project. There is no guarantee that doing any of the work yourself will save you money, especially if you have to buy tools and you put a value on your time. But if you enjoy physical work, have safe and reliable work habits, and take plea sure in shaping your own living space, you should do as much of the work as possible. Following are some ways to help cut costs by doing it yourself.

- Do the work of the highest paid professionals (usually plumbers and electricians).

- Do tasks that have a high labor cost relative to material costs, such as demolition, excavation, concrete work, wallboard finishing, and insulation.

- Do small jobs that would take a professional less than half a day, such as tiling countertops or installing vinyl flooring in a bathroom.

- Take charge of buying and delivering all materials.

Being the Project Manager

Managing a home improvement project is like running a small business. It requires careful planning, day-to-day attention to detail, the ability to deal with people in a variety of situations, a thorough understanding of each process, and basic ac counting skills.

Be prepared to spend enormous amounts of time. If you already have a full schedule, you will have to eliminate some things to manage your addition project. You will be successful if:

- You are organized, persistent, clear about the details of your project, and able to spend long hours on the telephone and at the job.

- You can handle money, make payments on time, and keep a budget.

- You are comfortable negotiating with subcontractors and suppliers.

- You are articulate and patient.

Hiring Professionals

If you hire a general contractor to oversee the entire project, you will still play an important role, especially in selecting the right contractor.

Contractor’s Estimate for a Small Addition

Permit fees

Site preparation and tool storage


Floor framing and subfloor

Wall framing and sheathing

Roof framing and sheathing

Roofing and gutters

Siding and exterior trim

Windows and doors

Exterior painting


Rough wiring


Finish walls and ceiling

Finish electrical


Trim and moldings

Interior painting

Floor covering

Debris removal



Overhead and profit 15%


























Scheduling Construction

The sequence of construction will vary with each job, but the following schedule applies to most additions.


- Arrange financing.

- Obtain permits.

- Order materials with long delivery dates.

- Line up subcontractors.


- Prepare site.

- Build forms and get inspection.

- Complete foundation.

Completion of Shell (Exterior)

- Frame floor system.

- Install underfloor utilities.

- Get inspections.

- Install subflooring.

- Frame walls and roof and alter house framing.

- Install sheathing.

- Install mechanical ducts.

- Install rough plumbing and gas lines.

- Install rough wiring, including recessed fixtures.

- Get inspections for utilities and framing.

- Apply roofing.

- Install windows and exterior doors.

- Install siding.

Completion of Interior:

- Remove original walls and so on within addition area.

- Install insulation and have it inspected.

- Apply wallboard or other wall material and get nailing inspection.

- Finish wall surface.

- Install trim and hang doors.

- Paint interior and exterior.

- Install floor underlayment.

- Install cabinets, shelves, and countertops.

- Install plumbing fixtures.

- Install built-in appliances.

- Install finish wiring.

- Install finish flooring.

- Install free-standing appliances (refrigerator, range).

- Complete trim and decorative details.

- Get final inspections.

Getting Ready for Construction

One of the most important steps in construction begins before you pound a nail: estimating the cost. It is also the most difficult. If you are bidding the work out to a general contractor or subcontractors, their bids will be your estimate. But if you manage the job yourself you will have to do your own estimate.

There are two kinds of costs to consider: predictable and hidden. To estimate predictable costs you break the project into smaller components, such as foundation work, framing, and roofing, and you estimate the labor and materials cost for each component. Use your plans to itemize materials and then get bid prices for the list from suppliers. Be sure to include easily overlooked items like nails, hardware, finish plumbing fixtures, light bulbs, and so on.

To estimate labor, break each component into discrete tasks, apply a time factor to them, and multiply the total time by known salary rates. You can estimate some components by getting bids from subcontractors.

You must also consider hidden costs: the surprises that turn a job into a nightmare and the nickel-and-dime costs that are easy to overlook but add up quickly. For additions, hidden cost factors often include:

  • Debris removal and dump fees A survey Engineering (for foundations, for example)
  • Landscaping
  • Rebuilding a chimney
  • Cleaning
  • Last-minute design changes
  • Power cords
  • Tool rentals
  • Blade replacement and sharpening
  • Difficult access
  • Upgrading existing features “while we’re at it” (such as a new roof)
  • Resizing gas lines
  • Matching obsolete materials
  • Inability to recycle existing materials as expected
  • Upgrading electric service

None of these cost factors may be obvious in the plans, but they are real and must be covered by the budget.

Preparing Yourself

While arranging all the details pertaining to the construction it's easy to overlook the importance of preparing yourself and your family. Any remodeling experience can be hectic. Be prepared for setbacks, disruptions, quick decision making, and constant mess. You can minimize the chaos by clearing sections of your garage, yard, or patio and devoting them to job logistics. You can ease the mental wear and tear by setting aside part of your budget for occasional dinners out or weekend vacations. Above all, look for times to enjoy the process, and keep a good sense of humor about it all.

Next: Simple Room Additions: Building the Foundation
Prev: Managing and Financing Your Project

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