Design Your Own Home Addition

  • Beginner
What You'll Need
Construction documents (drawn manually or with a computerized drafting program)
Required permits and approvals
Access to qualified consultants
List of reputable contractors and subcontractors

Designing your own home addition can be an enjoyable and rewarding experience, but one that requires extensive planning, preparation and a little research. There are many important things to think about before getting started. This article will cover the basics and offer a few suggestions about how to get through the design process.

Step 1 - The Conceptual Phase

First, decide in what direction you want to build—upward or sideways. You can avoid the considerable expense of building a concrete foundation by expanding on your existing attic. It is often possible to convert attic space into a comfortable living space without any major structural alterations. Adequate headroom can be provided simply by installing one or more dormers.

There are a few important design issues that will need to be addressed in the conceptual phase of the design process. What type of roof will the addition have? Gabled, hip, shed or another kind? What type of exterior cladding and trim? Choose design style and building materials that will allow the new addition to seamlessly merge with the existing building.

Step 2 - Critical Issues to be Resolved

If you are installing a new foundation, inquire at the building department about set back restrictions, floor area ratio and lot coverage ratio (if applicable). Will the new foundation be a slab on grade or a full basement? Determine how the new foundation will join to the existing foundation and if any underpinning is required.

If you are building up, there may be height limitations in the local building code. Also, an increase in inhabitable space may require an expansion of the septic system.

Step 3 - Come Up with a Plan

Your primary focus should be on occupancy and usage. Consider traffic flow, accessibility and convenience within the new space. You can likely get new ideas and inspiration from reference guides and publications at the local library that contain sample floor plans and home designs.

Remember to provide sufficient glazed (window) surface area to ensure that the new space has ample natural daylighting. The design of a one-story addition should be undertaken with an eye toward future expansion.

Step 4 - Get Help If You Need It

You might want to do as much as you can on your own, but you’ll probably need help in one or more of the following areas:

  • If you do not have the required computer skills or drafting ability, a draftsman can produce the necessary construction documents from rough sketches. You may find that a licensed architect can provide you with invaluable assistance throughout the entire process from conception to completion.
  • In addition to supplying construction documents, an architect can resolve design issues, expedite the filing process, obtain the required permits and approvals, and ensure that the addition will be in compliance with state and local building codes.
  • If any load bearing walls, beams or columns are to be removed, altered or affected in any way, you will need to consult with a professional engineer.

Finally, you will want to hire reputable and experienced contractors and subcontractors to build the addition.