A home-addition plot plan is not simply a drawing of the new room.

It places the proposed construction within the complete official lot so the reviewing authorities can understand how the project affects the existing building, required yards, lot occupancy, access, trees and adjoining public areas.

The drawing should make the proposed location measurable without requiring the reviewer to estimate distances or reconstruct the property from several disconnected documents.

For other residential projects in the District, including decks, garages, sheds, pools, fences and driveways, see our complete site plan for permit in Washington, DC service guide.

Why a Washington, DC Addition Needs a Plot Plan

A floor plan explains the rooms, walls, doors and interior arrangement of the addition. Elevations show its height and exterior appearance.

The plot plan answers a different set of questions:

• Which official lot is being developed?
• What buildings and improvements already exist?
• Where will the addition be placed?
• How large will the addition be?
• How far will it be from the rear and side lot lines?
• How will it affect the remaining yard?
• How will it change lot occupancy?
• Will it affect an alley, driveway or parking area?
• Are protected or significant trees near the work?
• Does the drawing agree with the floor plans and elevations?

DOB’s addition-permit guidance states that all additions—including increases in building length or height and the enclosure of an existing structure—must include a surveyor’s plat showing the existing and proposed structures and their dimensions.

Official source: DC Department of Buildings — Addition, Alteration and Repair Permit .

The Certified DC Building Plat Requirement

Washington, DC has a property-document requirement that homeowners sometimes overlook.

When applying for a permit involving exterior work—such as constructing an addition or deck—the applicant must include a building plat obtained from the DC Office of the Surveyor.

The official building plat establishes the record-lot framework used for the permit drawing. It shows:

• The official square and lot
• Official lot boundaries
• Recorded lot dimensions
• The lot’s legal shape

The completed permit plat should also show:

• Existing property improvements
• The proposed addition
• Project dimensions
• Other proposed exterior work
• Relevant trees

DOB’s building-plat guidance says the plat must show trees that are measured 4.5 feet above ground and have circumferences of at least 12 inches.

Official source: DC Department of Buildings — Get a Building Plat .

How to Obtain the Building Plat

The building plat can be ordered from the DC Office of the Surveyor through its online Citizens Access Portal.

Useful information to have before ordering includes:

• Complete property address
• Official square number
• Official lot number
• Property-owner information

After the existing and proposed improvements are drawn, the completed plat may need to be sent to the Office of the Surveyor for digital certification.

Official sources: Ordering a Building Plat Online and Get a Building Plat .

What the Addition Plot Plan Should Show

The exact submission requirements depend on the property and project. The following items are commonly relevant to a Washington, DC home addition.

Property address, square and lot

The plot plan should identify:

• Complete property address
• Official square number
• Official lot number
• Project title
• Short scope description
• Drawing or revision date

The property and project information should agree with the DOB permit application.

Complete existing house footprint

Show the entire existing dwelling rather than only the wall where the addition will connect.

Relevant existing features can include:

• Main house footprint
• Existing rear extensions
• Bay windows
• Covered porches
• Decks and balconies
• Exterior stairs and landings
• Cellar entrances
• Roofed projections

An incomplete existing footprint can produce inaccurate yard or lot-occupancy calculations.

Proposed addition footprint

The new construction should be clearly distinguishable from the existing house.

Use:

• A “PROPOSED ADDITION” label
• A distinct hatch pattern
• A different line weight
• Selective shading
• An existing-and-proposed legend

The complete proposed footprint may include:

• Exterior walls
• Covered areas
• Supporting posts
• Stairs and landings
• Areaways
• Roof projections
• Patios or paving added as part of the work

Addition dimensions

Show the overall length and width of the addition.

For an irregular project, provide enough measurements to define the complete shape.

The dimensions should agree with:

• Floor plans
• Exterior elevations
• Foundation plans
• Structural drawings
• The permit application

A plot plan showing a different addition size from the architectural plans can result in a correction request.

Distances to lot lines

The drawing should provide measurable yard information around the proposed addition.

Depending on the property, this can include:

• Remaining rear-yard depth
• Left-side yard
• Right-side yard
• Front setback or building-line relationship
• Distance to a public alley
• Court dimensions
• Distance to another building

Do not use a backyard fence as the official rear lot line unless reliable property documentation confirms that relationship.

DC Yard Requirements Vary by Zone and Property

There is no single rear- or side-yard number that applies to every Washington, DC addition.

The controlling requirement may depend on:

• Zoning district
• Building type
• Detached, semi-detached or rowhouse configuration
• Lot dimensions
• Existing building placement
• Corner-lot conditions
• Alley relationship
• Overlay or historic status
• Previous zoning orders or approvals

Before finalising the proposed addition, research the property using the official DC zoning map and review the regulations for the identified zone.

Official source: DC Office of Zoning — Official Zoning Maps .

For general guidance, read Setbacks and Zoning: How to Find the Rules for Your Property .

Lot Occupancy for a DC Home Addition

A proposed addition may satisfy its yard requirements but still be limited by maximum lot occupancy.

Lot occupancy generally compares the portion of the lot occupied by buildings or structures with the complete lot area, using the definitions and rules applicable to the property.

The plot plan may need to identify:

• Total official lot area
• Existing principal-building footprint
• Existing accessory-building area
• Other areas included under the applicable zoning definition
• Proposed addition footprint
• Total proposed occupied area
• Existing lot-occupancy percentage
• Proposed lot-occupancy percentage
• Maximum permitted lot occupancy

The plot plan should state where the lot area and building-area figures came from and should remain consistent with the rest of the permit drawings.

Rear Additions on Rowhouse Properties

Rear additions are common on Washington rowhouses, but they can involve several overlapping site issues.

The plot plan may need to show:

• Existing rear wall of the house
• Proposed rear-wall location
• Length of the proposed extension
• Remaining rear-yard depth
• Relationship to neighbouring building walls
• Existing deck or porch removal
• Rear stairs and landings
• Public alley
• Garage or parking pad
• Fences and retaining walls
• Trees near excavation
• Existing and proposed lot occupancy

The drawing should not imply that a neighbouring structure, fence or alley edge is the property boundary unless that information is supported by the official plat or a licensed survey.

Side Additions and Detached Homes

A side addition may affect:

• Required side-yard width
• Building separation
• Driveway access
• Windows and exterior openings
• Utility routes
• Trees and excavation
• Front-building alignment
• Lot occupancy

Show both the existing and proposed side-yard dimensions. The plan should also identify any driveway or side access that will be narrowed or removed.

Alleys, Parking and Rear Access

Many DC residential lots rely on a public alley for parking, garage access, waste collection or construction access.

The addition plot plan may need to identify:

• Public alley location and width when available
• Garage or parking pad
• Existing and proposed parking
• Vehicle-access path
• Gates
• Rear-yard stairs
• Construction-access area
• Waste-storage area when relevant

A rear addition should not be shown in isolation when it changes access to an existing garage or parking area.

Trees Near the Addition

DOB’s building-plat guidance requires qualifying trees to be shown on the plat.

Trees can also affect:

• Foundation excavation
• Construction access
• Utility trenching
• Retaining-wall work
• Demolition
• Temporary material storage
• Driveway or paving changes

The plot plan may identify:

• Tree locations
• Tree circumference or size
• Distance from the proposed addition
• Whether the tree will remain or be removed
• Tree-protection areas when supplied

Separate Urban Forestry approval or arborist information may be required depending on the tree and proposed impacts.

Party Walls and Neighbour Notification

DOB’s addition guidance states that neighbour notification is required when work includes construction on a property line or party wall.

The plot plan and construction drawings should clearly identify:

• Property-line location
• Party-wall location
• Existing neighbouring structures
• Proposed construction at or near the line
• Excavation or foundation relationship

The plot plan alone does not replace party-wall details, structural drawings or required notification documents.

Public Space and Front-Yard Work

Some front-yard areas that appear to belong to the house are public space between the private property line and the street curb.

When an addition project also changes front steps, retaining walls, fences, walkways, curb cuts or other public-space features, separate DDOT approval may be required.

Show the distinction between:

• Private property
• Public sidewalk
• Tree space
• Driveway apron
• Street or parking lane

Official source: DDOT Public Space Permit Requirements .

Historic Properties

Properties within a historic district or individually designated as historic may require preservation review for exterior additions.

Historic review can affect:

• Addition height
• Visibility from public streets
• Rear-extension design
• Roof form
• Exterior materials
• Window and door arrangement
• Demolition of existing features

Confirm the property’s historic status early, before finalising the plot plan and architectural drawings.

Official source: DC Office of Planning — Building Permits for Historic Property .

Plot Plan vs Floor Plans and Elevations

The dimensions and project description should remain consistent across every drawing.

Current DOB Submission Process

DOB currently uses an online checklist and electronic submission process for residential projects.

DOB requires the completed project checklist to be included with the ProjectDox documentation.

Official source: DC Department of Buildings — ProjectDox .

A Wall Check May Be Required During Construction

Some additions require a wall check after foundation walls or other exterior construction features are placed.

A wall check is used to confirm that the constructed work matches:

• The approved building plat
• The approved permit drawings
• Property-line relationships
• Required yards

A wall check is a later field-verification service. It is not replaced by the original addition plot plan.

Official source: DC Department of Buildings — Wall Checks .

Information to Send With Your Plot Plan Order

How Our DC Addition Plot Plan Service Works

1. Place your order. Select the site-plan option matching the required level of detail.
2. Upload the building plat. Provide the official DC Surveyor base document.
3. Describe the addition. Include the proposed length, width, height and number of levels.
4. Upload the project drawings. Send floor plans, elevations, sketches and photographs.
5. Review the completed draft. Confirm the project position, dimensions and labels.
6. Coordinate the certification process. Follow the current Office of the Surveyor instructions when digital certification is required.
7. Submit with the complete permit package. Include the required architectural, structural and supporting documents.

The accuracy and usefulness of the drawing depend on the building plat, architectural information, photographs and dimensions supplied.

Common DC Home Addition Plot Plan Problems

• The certified DC building plat is missing
• The wrong square or lot is used
• The complete existing house is not shown
• The proposed addition is not clearly labelled
• Addition dimensions are missing
• Rear-yard depth is unclear
• Side-yard dimensions are omitted
• Lot occupancy is missing when required
• The plot plan and floor plans show different addition sizes
• Existing decks, stairs or porches are omitted
• The alley, garage or parking area is not shown
• Trees near the construction area are omitted
• A fence is used as the assumed property line
• Public space is shown as private property
• Party-wall or property-line construction is not identified
• Historic status is discovered late
• The required residential checklist is not uploaded
• A drafted plan is submitted where professional certification is required

A complete plot plan cannot guarantee permit approval, but it can reduce correction requests caused by missing or inconsistent site information.

Read What Permit Reviewers Check First on a Site Plan and Why Site Plans Get Rejected for Permits .

Washington, DC Home Addition Plot Plan Checklist

Frequently Asked Questions

Does a Washington, DC home addition require a building plat?

Yes. DOB states that additions must include a surveyor’s plat showing the existing and proposed structures and their dimensions.

Can USA Site Plans issue the official building plat?

No. The official building plat must be obtained from and certified through the DC Office of the Surveyor. USA Site Plans can draft the proposed addition using the supplied plat as the base.

What should the addition plot plan show?

It should generally show the official lot, existing house, proposed addition, project dimensions, yard measurements, access, relevant trees, a north arrow and a drawing scale. Lot-occupancy information may also be required.

What is lot occupancy?

Lot occupancy compares the building or structure area counted under the applicable zoning rules with the total lot area. The permitted percentage and the features included in the calculation vary by zone and property.

What rear-yard setback applies to my addition?

There is no universal distance for every DC property. The requirement depends on the zoning district, building type, lot and other property-specific conditions.

Can I use a fence as the rear property line?

Not automatically. The official building plat or a licensed survey should be used to establish the relevant lot-line information.

Do I need floor plans and elevations too?

Yes. DOB’s addition guidance requires floor plans showing the existing and proposed structures. Elevations, sections, structural plans and other documents may also be required according to the project.

Do trees need to appear on the building plat?

DOB’s building-plat guidance says the plat must show trees measured 4.5 feet above the ground with circumferences of at least 12 inches.

What happens when the addition touches a party wall?

DOB states that neighbour notification is required when work includes construction on a property line or party wall. Structural and notification documents may be required in addition to the plot plan.

Are USA Site Plans drawings signed or sealed?

No. USA Site Plans provides drafting services. DC architectural, engineering or land-surveying seals must be obtained separately when required.

Will the plot plan guarantee permit approval?

No. DOB, zoning reviewers and any participating agencies control approval and may request revisions, calculations, licensed surveys or professionally sealed drawings.

Official Washington, DC Sources

• DOB — Addition, Alteration and Repair Permit
• DOB — Get a Building Plat
• DOB — Ordering a Building Plat Online
• DOB — How to Get a Permit
• DOB — ProjectDox
• DC Office of Zoning — Official Zoning Maps
• DDOT — Public Space Permit Requirements
• DC Office of Planning — Historic Property Permits
• DOB — Wall Check Requirements

Disclaimer: This article provides general educational information and is not legal, surveying, engineering, architectural, zoning or permitting advice. Washington, DC requirements vary according to the property, zoning district, building type, historic status, trees, public space and project scope. USA Site Plans is an independent drafting service and is not affiliated with the DC Department of Buildings, DC Office of the Surveyor, Office of Zoning or DDOT. A drafted plot plan does not establish legal property boundaries or replace a certified DC building plat, licensed survey, architecture, structural engineering or another professionally sealed document when required.