What to Expect When Applying for Building Permits
When planning a home renovation or addition in D.C., it is crucial to understand the permitting process which requires signed plans from a registered architect, along with stamped drawings from a structural engineer and an MEP (Mechanical, Electrical, and Plumbing) engineer. These engineers are typically contracted through the architect. Depending on the scope of the project, a civil engineer may also be required to handle site and utility permits.
Permit applications for one or two-dwelling units begin by filling out an application form at D.C. Permit Wizard. After submission and payment of the application fee, an email will be sent with instructions to upload drawings and documentation to Project Docx. These documents include architectural plans as well as structural and MEP engineer drawings.
Once all documents are submitted, the review process begins. The first step is pre-screening to confirm all required drawings are uploaded. After pre-screening, the project is sent to reviewers, who are assigned randomly. All reviews must be completed before a review cycle can close. After the cycle closes, the design team can respond to review comments. The process continues until all reviewers approve the project.
D.C. Permit Requirements for Interior Renovations
For interior renovation projects, D.C. requires architectural drawings detailing the demolition and proposed floor plans, as well as structural drawings showing any structural changes. Additionally, MEP (Mechanical, Electrical, and Plumbing) drawings are required. DC is unique in the DMV area in that it mandates MEP drawings for interior renovations.
If the existing water line is less than 1 inch in diameter, it can only support one additional full bathroom. The size of the water line can be found on the water bill. If additional plumbing is involved, a D.C. water form must be completed to ensure the existing water line is sufficient to support the new fixtures. Architects can assist with completing this form.
Converting the Basement into a Separate Unit
D.C. zoning regulations support accessory dwelling units (ADUs) or independent units in the basements or cellars of townhouses and single-family homes. A basement apartment can be a great source of income, whether for short or long-term rental.
The first step in this process is to review the property’s zoning. Most residential (R) zones allow ADUs by right. Additionally, DC has a Residential Flat (RF) zone, which permits two units within a single building. The key difference between an ADU and a two-unit dwelling is that an ADU is accessory to the main house, while a two-unit dwelling consists of two fully independent apartments.
Beyond zoning requirements, the building code applies the same standards to both ADUs and independent units regarding fire rating, sound insulation, and other safety measures. If underpinning is required to increase the basement or cellar ceiling height, neighbors must be notified. An architect can guide the client through the neighbor notification requirements.
Considerations for Home Additions
Home additions are an excellent way to expand a home while staying in the same neighborhood. However, adding space to a townhouse or detached home involves several important considerations.
Rear Additions
A proposed rear addition must comply with rear setback and lot coverage requirements. In D.C., a rear addition is limited to extending 10 feet beyond the nearest neighbor’s rear wall by right. This rule was introduced to prevent large additions on deep lots from restricting light and air for neighboring properties. Rear additions exceeding 10 feet may be approved through a special exception. These exceptions are common and typically granted if the request is reasonable.
Vertical Additions
Adding an additional floor requires thorough due diligence at the start of the project.
Several key factors must be considered:
- Neighboring Chimneys: If a neighboring chimney is within 10 feet of the proposed addition and is functional, an agreement may be required to extend it. Without an agreement, the vertical addition may not be feasible.
- Snow Drifting Concerns: D.C. regulations consider the potential impact of snow drifting from the new addition onto a neighbor’s roof, which could create structural issues. A structural engineer will conduct snow drift calculations to assess this risk.
- Structural Loads: The structural engineer must also confirm that the existing foundation can support the additional load from the new floor.
- Neighboring Solar Panels: Another consideration is whether any of the immediate neighbors have solar panels on their roofs. Zoning rules prohibit vertical additions that significantly impact the sun exposure on the neighbor’s solar panels.
- Architectural Features: To preserve the character and scale of D.C. streetscapes, zoning regulations prohibit the demolition of significant roof architectural features, such as dormers. In such cases, the vertical addition must be set back at least three feet from the architectural feature.
By addressing these factors early in the planning process, homeowners can better navigate zoning and additional requirements for a successful vertical addition.
Axis Architects + Interiors has successfully completed numerous vertical additions to townhouses in DC and can provide clear guidance from start to finish. For additions to detached homes, the process is generally simpler. However, homeowners should still consult an architect familiar with zoning regulations early in the process to determine what is permissible for their lot.
Other Important Considerations
Historic Districts
Any additions in a historic district in D.C. falls into the purview of the historic preservation office under (HPO). Each historic district is assigned a specific HPO staff member, and their contact information can be found at the Historic Preservation Office. Your architect should be able to facilitate the initial discussion with the HPO staff at the early stages of the design process. If an addition is visible from a public street or exceeds 500 square feet, it may require full approval from the Historic Preservation Review Board (HPRB).
Axis Architects + Interiors has had many projects approved by HPRB and can guide you throughout the process.
DDOT
In D.C. it is not uncommon to see architectural features like porches, bay windows, window wells, or exterior stairs extend beyond the property and into the right-of-way (ROW). D.C. regulations allow these encroachments under specific guidelines that regulate their sizes and proportions. Architects can ensure the designs comply with these guidelines and help the homeowners submit an application to DDOT for approval.
Heritage Trees
D.C. has strict regulations regarding heritage trees. The heritage tree designation depends primarily on the tree’s size and the species, and they typically cannot be removed. Homeowners should work with an arborist to determine if large trees on their property or their neighbor’s property are heritage trees. A tree protection plan, prepared by an arborist, is required, and the size of the addition may be impacted due to the tree’s critical root zone. Axis Architects + Interiors has experience in planning projects around heritage trees, see one example here.
Board of Zoning Adjustments (BZA)
The BZA special exceptions process can grant certain relief from zoning requirements which can increase the size of the addition. While this process may extend the project timeline, it often benefits the homeowner. Axis Architects + Interiors is experienced in handling BZA special exception cases and can help the homeowner navigate the process.
Sprinkler Requirements: Do You Need Them?
Sprinkler requirements for additions or renovations can be confusing. Residential buildings with up to two units are governed by the International Residential Code (IRC), which mandates sprinklers only in certain situations. The sprinkler system, if required, is a NFPA 13D system which is the lowest grade of sprinkler system. The D.C. existing building code amends the IRC and states the following when it comes to sprinklers.
For Additions
International Existing Building Code
1102.3 Fire protection systems. Existing fire areas increased by the addition shall comply with Chapter 9 of the Building Code for buildings that are under the jurisdiction of the Building Code. Existing fire areas increased by the addition shall comply with Section 313 of the Residential Code for buildings under the jurisdiction of the Residential Code.
Exceptions Include:
- An automatic sprinkler system shall not be required for buildings under the jurisdiction of the Residential Code where the addition is less than 50 percent of the building area of the existing building and the water service is not being replaced.
- An automatic sprinkler system shall not be required for buildings under the jurisdiction of the Residential Code where the existing water service cannot provide adequate flow and pressure without the installation of a tank or pump, unless the water service is otherwise being replaced.
For Renovations Requirements
This is for major renovations that fall under level 3 alterations.
International Existing Building Code:
904.1.4 Group R-3 and Residential Code buildings. An automatic sprinkler system shall be provided in all buildings with Group R-3 occupancies and in all buildings subject to the Residential Code.
Exceptions Include:
- An automatic sprinkler system shall not be required in Group R-3 occupancies under the jurisdiction of the Building Code where the existing water service cannot provide adequate flow and pressure without the installation of a tank or pump, unless the water service is otherwise being replaced.
- An automatic sprinkler system shall not be required for buildings under the jurisdiction of the Residential Code where the existing water service cannot provide adequate flow and pressure without the installation of a tank or pump, unless the water service is otherwise being replaced.
Sprinklers are not required if the existing water service is inadequate and needs to be replaced. The architect, plumbing, and civil engineers can help you evaluate the existing water line.
Decoding D.C. Home Additions with Axis Architects + Interiors
Navigating D.C.’s zoning and building regulations for home additions and renovations requires careful planning and expert guidance. Whether you're considering a rear or vertical addition or converting a basement into a separate unit, understanding the requirements early in the process is crucial to avoid complications later.
While some projects may require special exceptions or historic approvals, working with experienced architects and consultants can help streamline the approval process and prevent potential setbacks—especially during construction, as non-compliance could result in a stop-work order. With the right approach, homeowners can successfully expand and enhance their properties while staying compliant with DC’s regulations and ensuring a smooth process.
At Axis Architects + Interiors, we are dedicated to creating beautiful and functional spaces tailored to your unique needs. Contact us today to bring your vision to life!
