K-One Design & Build · Established 1987

Love Your Neighborhood. Need More House?

Thoughtfully designed home additions in McLean, Arlington, and Northern Virginia-creating the space you need without leaving the community you love.

AI-generated concept of an elegant, open-plan home addition with expansive windows looking toward a wooded garden
Since 1987Family-operated firm
Design + BuildCoordinated services
Northern VirginiaLocal project experience
Home addition services

More Space. A Better Way to Live.

From expanding your living area to adding a second story, we help homeowners assess what is possible and plan additions that fit their homes and lifestyles.

AI-generated design concept showing an open-plan rear addition with garden views

Rear & Main-Level Additions

Expand your kitchen, family room, or main-level living area with a cohesive connection to the original home.

Discuss this addition →
AI-generated concept depicting a bright bedroom and upper-floor living space

Second-Story Additions

Explore upward expansion for bedrooms, bathrooms, or a primary suite while preserving more of your outdoor space.

Explore feasibility →
AI-generated concept of a light-filled renovated family room

Additions & Whole-Home Renovations

Coordinate the new addition with improvements throughout the existing home for a consistent, functional result.

Plan a transformation →
AI-generated architectural design concept with plans and finish materials
The K-One approach

An Integrated Design-Build Experience

An addition involves much more than adding square footage. The new space must work with the original structure, layout, rooflines, utilities, and property constraints.

K-One brings architectural design, structural engineering expertise, permitting coordination, and construction experience together to guide the work from early planning through completion.

  • Assess the home, property, and scope
  • Consider zoning and structural feasibility
  • Develop architectural plans and coordinated details
  • Navigate permits and plan construction
Our process

From First Conversation to Finished Addition

01 / CONSULT

Understand Your Goals

Review your needs, location, initial scope, desired timeline, and investment expectations.

02 / EVALUATE

Explore Feasibility

Consider site limitations, existing conditions, major structural requirements, and design opportunities.

03 / DESIGN

Design & Approvals

Develop the project documents and coordinate required review and permitting.

04 / BUILD

Construct & Finish

Manage the construction work, details, and finishing stages through completion.

AI-generated inspiration for a comfortable, light-filled family-room addition
Design that belongs

The Best Addition Feels Part of the Home

A successful addition respects the architecture of the original home while improving everyday circulation, natural light, and comfort. Rooflines, floor transitions, exterior finishes, and the relationship between rooms all matter.

See K-One's actual work to understand our approach to residential design and construction.

Explore Our Portfolio →
Home addition FAQs

Questions Northern Virginia Homeowners Ask

Can I build a second story on my home?

Potentially. Structural capacity, foundation conditions, zoning, building height limits, and the scope of reinforcement all affect feasibility. The best starting point is a project-specific evaluation.

How much does a major home addition cost?

Costs depend on area, complexity, structural modifications, foundation and site work, mechanical systems, and finishes. We prefer to review the proposed scope and existing home before discussing a realistic range.

Do additions require permits in McLean or Arlington?

Generally, yes. Building permits are usually needed, and additional zoning, grading, or site-related approvals may apply depending on the property and the work.

Can the addition match my existing home?

Matching roof geometry, materials, window proportions, floor levels, and architectural details is part of planning a thoughtful addition.

Should I renovate, add on, or rebuild?

That depends on the home's condition, lot constraints, your desired layout, and the total investment. Comparing alternatives early can prevent costly decisions later.

Make space for what's next

Ready to Explore the Possibilities?

Tell us about your home addition in McLean, Arlington, Great Falls, or the surrounding Northern Virginia area.

Schedule a Home Addition Consultation →
K-One Design & Build · Established 1987