04 —Service
Home Additions
Sunrooms, master suites, second stories — we add the space your family needs.
Typical Investment
$75,000 – $500,000
Based on 153 completed MOSS projects. Median investment: $250K.
03 —Common Questions
Everything you want to know about home additions
How much does a home addition cost in the DC metro area?
Home additions in the DMV typically cost $150–$350 per square foot, with most MOSS projects ranging from $150K to $500K depending on size and complexity.
Single-story bump-outs (200–400 SF) start around $100K. Two-story additions and pop-tops run $300K–$600K+. The biggest cost drivers are foundation type, structural complexity, and finish level.
How long does a home addition take?
Most MOSS additions take 4–7 months from permit to completion.
Foundation and framing take 4–6 weeks. Roofing, siding, and MEP rough-in add 3–4 weeks. Interior finishes run 4–8 weeks depending on complexity.
Do I need an architect for a home addition?
MOSS handles design and engineering in-house, eliminating the need for a separate architect.
Our design team creates schematic layouts, 3D renderings, and full construction drawings. For structural work, we engage licensed engineers as part of our standard process.
What types of additions does MOSS build?
MOSS builds bump-outs, sunrooms, second-story additions (pop-tops), garage conversions, and in-law suites.
Each addition type has different structural requirements, permit implications, and cost profiles. Pop-tops require temporary roof removal and structural engineering. Bump-outs are the most cost-efficient way to add square footage.
04 —Materials Guide
Compare your options
Top 4 Addition Types for DMV Homes
Pop-Top (Second Story)
Doubles livable space without expanding the footprint.
Rear Bump-Out
The most cost-efficient way to expand a kitchen or family room.
In-Law Suite
Self-contained living space for multi-generational families.
Sunroom/Four-Season Room
Year-round outdoor living with climate control.
3 Things to Know Before Your Home Addition
Setback requirements limit your options
Every jurisdiction has setback rules. Check before you design.
Foundation type affects everything
Slab, crawl, or full basement — this decision drives cost and timeline.
Tie-in is the hardest part
Where new meets old is where craftsmanship matters most. Rooflines, siding, and interior transitions require expert execution.
Our pop-top gave us three bedrooms and a bathroom we didn't have. The kids finally have their own rooms.
05 —Portfolio
Home Additions projects
How does home additions look in real homes?
Viola Street Springfield Home Addition
South Wakefield Home Addition
Silverleaf Drive Home Addition
Lorcom Court Home Addition
Dorset Drive Home Addition
Wake Forest Drive Home Addition
Cobb Hill Lane Two-Story Home Addition
Ox Croft Court Home Addition
S Pollard Street Second Story Addition
Banbury Drive Home Addition
S. Pollard Street Home Addition
Bethel Road Home Addition
Service Area
Where MOSS builds additions
Other Services
Other ways MOSS transforms your home
06 —FAQ
Frequently asked questions
- How much does a home addition cost in the DC metro area?
- Home additions in the DMV typically cost $150–$350 per square foot, with most MOSS projects ranging from $150K to $500K depending on size and complexity. Single-story bump-outs (200–400 SF) start around $100K. Two-story additions and pop-tops run $300K–$600K+. The biggest cost drivers are foundation type, structural complexity, and finish level.
- How long does a home addition take?
- Most MOSS additions take 4–7 months from permit to completion. Foundation and framing take 4–6 weeks. Roofing, siding, and MEP rough-in add 3–4 weeks. Interior finishes run 4–8 weeks depending on complexity.
- Do I need an architect for a home addition?
- MOSS handles design and engineering in-house, eliminating the need for a separate architect. Our design team creates schematic layouts, 3D renderings, and full construction drawings. For structural work, we engage licensed engineers as part of our standard process.
- What types of additions does MOSS build?
- MOSS builds bump-outs, sunrooms, second-story additions (pop-tops), garage conversions, and in-law suites. Each addition type has different structural requirements, permit implications, and cost profiles. Pop-tops require temporary roof removal and structural engineering. Bump-outs are the most cost-efficient way to add square footage.
Start your home additions project
One conversation reveals exactly what your project will involve and what it will cost.