2026 GUIDE • WASHINGTON DC

How much does a rear addition permit cost in Washington DC in 2026

Most rear additions in Washington DC cost $1,500 – $6,000 in permit fees in 2026, with the total driven by declared construction value, plan review depth, and the District’s technology and enhancement surcharges.

A rear addition is one of the most common ways DC homeowners add space without a second story. It is a residential building permit from the DC Department of Buildings (DOB), and because it involves new foundation, framing, and roof work, it lands in a higher fee tier than an interior remodel.

Cost breakdown (2026)

Fee component	Typical 2026 cost
Filing fee	$32
Base permit fee (tiered by construction value)	$500 – $3,000
Plan review (structural, egress, life safety)	$250 – $1,100
Electrical / mechanical / plumbing add-ons	$200 – $600
Technology fee (10%)	~10% of permit fee
Enhancement fee (6%)	~6% of permit fee
Zoning fee (lot occupancy / rear yard)	$50 – $150
Typical total	$1,500 – $6,000

Rear additions frequently pair with a second story or a basement suite — see DC second story addition permit costs and DC in-law suite permit costs for the fee picture across related scopes.

The single most expensive mistake on a rear addition is discovering a zoning conflict after design. Rear-yard setback and lot-occupancy limits vary by zone, and an addition that pushes past the allowed envelope can require relief — a process measured in months, not days, and in separate fees, not just redesign.

What affects the price

• Declared construction value. The dominant driver. Rear additions commonly declare $100,000 – $400,000, landing in mid-to-high fee tiers.
• Plan review depth. Structural, egress, and life-safety review all apply to new construction attached to an existing home.
• Zoning and lot occupancy. Rear-yard and coverage rules frequently trigger a zoning review, fee, or relief.
• Historic district or HPRB review. Rear additions in historic districts may still require Historic Preservation Review Board review if visible.
• Depth and footprint size. A shallow bump-out declares far less than a full-width, full-depth addition.
• Expedited processing. Available for an added fee when schedule matters.

How the fee is calculated

DOB uses a formula under the DOB fee schedule (2026), not a flat rate per square foot:

1. Filing fee: roughly $32, charged up front.
2. Base permit fee: tiered by declared construction value — roughly $148 for the first $1,000 of value, then approximately $10 per additional $1,000. Minimum flat tiers for very low-value work run around $33 – $65.
3. 10% technology fee: added on top of the permit fee.
4. 6% enhancement fee: also added on top.
5. Zoning fee: where a zoning review applies.

The key takeaway: fees scale with declared construction value. Because rear additions declare six-figure values, the permit fee climbs well above interior alterations, and the 10% and 6% surcharges scale with it.

Worked example: a $220,000 rear addition lands near $2,338 in base fees before surcharges (about $148 plus roughly $2,190 in per-thousand charges). The 10% technology and 6% enhancement fees add roughly $374, and plan review plus trade permits push the total into the upper-middle of the range.

Timeline & steps

1. Feasibility and zoning check. Setbacks, lot occupancy, and historic status — 2 – 5 weeks.
2. Architectural and structural design. Full drawing set with foundation and framing — 5 – 10 weeks.
3. File via CitizenAccess. Submit to DOB through the CitizenAccess portal.
4. Plan review: typically 4 – 12 weeks; structural and zoning reviews are the long poles.
5. Permit issuance, construction, and inspections. Framing, electrical, mechanical, and final inspections close out the work.

Common mistakes

• Skipping the zoning envelope check. Discovering a rear-yard violation after design wastes months and money.
• Incomplete structural drawings. Foundation and framing completeness is the top resubmittal driver for additions.
• Forgetting trade permits. Electrical, mechanical, and plumbing permits stack on top of the building permit.
• Under-declaring construction value. DOB reconciles declared value against drawings; a lowball triggers corrections and delay.

FAQ

Do I need a permit to build a rear addition in DC?

Yes. A rear addition is new construction attached to an existing home and requires a building permit, plus trade permits for electrical, mechanical, and plumbing work.

Is plan review required?

Yes. Additions are reviewed for structural adequacy, egress, and life safety. There is no simple over-the-counter path for new construction of this scale.

Could a rear addition require zoning relief?

Possibly. Rear-yard setback, lot-occupancy, and height rules can require a variance or special exception, adding time and separate costs.

How much do rear additions typically declare in construction value?

Commonly $100,000 – $400,000, which is why the permit fee is meaningfully higher than for an interior remodel.

How long does approval take?

Plan on 3 – 6 months from filing to permit, longer where zoning relief or historic review is involved.

Disclaimer

Figures on this page are 2026 estimates based on the DC Department of Buildings fee schedule. Fee schedules change; always verify current amounts with DOB directly or through the CitizenAccess portal before filing. This article is informational and is not legal or financial advice.