What does a home addition cost in Washington, DC?

What published figures say about additions in DC

The gap between an $80,163 average and a $170,517 suite is the difference between a small room and a bedroom with a full bath. Neither is a quote.

• Angi's Washington, DC page gives an average home addition cost of $80,163, with most homeowners paying between $39,053 and $121,601 (<a href="https://www.angi.com/articles/how-much-do-home-additions-cost/dc/washington" class="text-orange-700 font-bold hover:underline" rel="noopener">Angi</a>).
• Angi puts a second-story addition in DC at $400 to $800 per square foot, with an average total of $190,575 (<a href="https://www.angi.com/articles/cost-add-second-story/dc/washington" class="text-orange-700 font-bold hover:underline" rel="noopener">Angi, second story</a>).
• The 2025 Cost vs. Value report's national table puts a midrange primary suite addition at $170,517 and an upscale one at $351,613 (<a href="https://www.jlconline.com/cost-vs-value/2025/national/" class="text-orange-700 font-bold hover:underline" rel="noopener">Cost vs. Value 2025</a>).

How much does a home addition cost in Washington DC?

We do not publish our own figure, because in DC the lot sets the price as much as the room does. Most District additions go on the back of a row house or semi-detached house, where zoning limits lot occupancy and sets the rear yard, materials come in by the alley, and the shared walls and old footings next door have to be protected.

In a historic district, the Historic Preservation Review Board reviews the addition before the Department of Buildings issues a permit. Those steps cost time and design fees before construction costs anything. The walkthrough is free, and the price comes in writing once drawings exist. Our Washington, DC page covers the local rules.

What is the cost per square foot for an addition in Maryland?

A per square foot figure is a poor guide for an addition, which is why we do not give one. The foundation, the roof tie-in, the opening into the house and any new heating or electrical capacity cost about the same whether the room is 150 or 300 square feet, so small additions cost far more per foot than large ones.

A bathroom or kitchen inside the addition raises it again. In Maryland, add the county permit, and on a house with a well or septic, the Health Department review for a new bedroom.

Is it cheaper to build up or build out?

It depends on the house, and neither wins by rule. Building out pays for a new foundation and a new roof. Building up skips the foundation, but it pays for opening the roof, checking and often strengthening the walls and footings below, a staircase that takes space from the floor beneath, and often a stretch living elsewhere while the house is open.

On a lot where the setbacks leave no room to build out, up is the only option. Our guide to addition types compares the two for daily life as well as cost.

How much does a primary suite addition cost?

More than a bedroom addition of the same size, because a primary suite carries a full bathroom and usually a walk-in closet. The bathroom brings drain runs back to the house, waterproofing, tile and fixtures, which makes it the most expensive part of the addition per square foot.

A ground-floor suite on its own foundation is a common choice for a household planning to stay as it ages. The written estimate prices the bedroom shell and the bathroom on separate lines, so you can see where the money goes.

Does an addition cost more than moving to a bigger house?

The construction can cost more than the price gap between two houses, but moving has costs that build nothing. Selling and buying in DC, Maryland or Virginia brings agent commissions, transfer and recordation taxes, closing costs, the move itself, and often a higher mortgage rate than the one you have.

An addition keeps the neighborhood, the school and the rate. Compare the full cost of moving against a written price for the addition, not against a guess.

Why do additions go over budget so often?

Most overruns come from four places: changes made after the drawings were priced, allowances set too low for what gets chosen, conditions found where the addition meets the old house, and surprises in the ground at the footings, like rock, soft soil or a buried line.

The first two are yours to control. The last two are handled by a contract that states what it assumes and prices any difference as a written change order before the work. The contract checklist lists what else to look for.

How we price an addition

The first visit looks at the lot, the setbacks and the house, and tells you what the drawings will need. Once drawings and engineering exist, the price is written stage by stage, foundation, framing and roof, the opening into the house, the trades and the finishes, with the approvals shown apart from the build. Any change after that is priced in writing before it is built.

Where these numbers come from

Figures are quoted exactly as published. No contractor's own pricing was used.

• Angi, home addition cost in Washington, DC, checked October 2026: average and typical range. <a href="https://www.angi.com/articles/how-much-do-home-additions-cost/dc/washington" class="text-orange-700 font-bold hover:underline" rel="noopener">angi.com</a>
• Angi, cost to add a second story in Washington, DC, checked October 2026: per square foot range and average total. <a href="https://www.angi.com/articles/cost-add-second-story/dc/washington" class="text-orange-700 font-bold hover:underline" rel="noopener">angi.com</a>
• Cost vs. Value 2025 (JLC and Zonda), national table: primary suite addition job cost. <a href="https://www.jlconline.com/cost-vs-value/2025/national/" class="text-orange-700 font-bold hover:underline" rel="noopener">jlconline.com</a>