Home additions, second stories & ADUs
Room additions, second-story additions, garage additions, in-law suites and accessory dwelling units in Maryland, from drawings and permits through final inspection.
Typical range: $200 – $475 per SF
What’s included
- Feasibility check: zoning, setbacks and lot coverage
- Architectural drawings and engineering through our partners
- Permits and inspections
- Foundation, framing, roof tie-in and exterior match
- Interior finishes and final walkthrough
What drives the price
| Factor | Lower end | Higher end |
|---|---|---|
| Size | Single room | Two-story / full ADU |
| Foundation | Slab | Full basement |
| Plumbing | None | Kitchen and bath |
| Exterior | Simple match | Complex roof tie-in |
Additions & ADUs FAQ
Do I need drawings?
Yes. Additions need stamped drawings and a permit. We coordinate the drafter and engineer for you.
Can I build an ADU on my lot?
It depends on your county and zoning. We check setbacks, lot size and ADU rules before you spend on design.
How are payments handled?
Payments follow construction milestones, with a deposit no larger than one-third as Maryland law requires.
Can you build a second story on my house?
Often, yes. It depends on the existing foundation and framing and on your county’s height limits. We check the structure and zoning before design starts.
Do I need to move out during an addition?
Usually not. We keep the work closed off from the rest of the house. For second-story additions there may be a few days when part of the house is unusable while the roof is open.
Will the addition match my house?
That is the goal. We match rooflines, siding, windows and trim so the addition looks like it was always there.
Types of additions
Ways to add space to your home
Room additions
A family room, primary suite, bigger kitchen or home office built off the side or back of the house.
Second-story additions
Build up instead of out. Ideal when the lot is tight. We check the existing foundation and framing first, then add a full or partial second floor.
In-law suites
A bedroom, bath and living area for parents or adult kids, attached to the house with its own entrance if you want one.
Garage additions
Attached garages, garage conversions and space over the garage, permitted and built to match the house.
ADUs
A detached or attached accessory dwelling unit with its own kitchen and bath, where your county and zoning allow it.
Bump-outs
Small additions that make a kitchen, bath or closet work without a full addition.
Budget
Home addition cost examples
Most additions we price run $200 to $475 per square foot, depending on the type. Here is what that looks like for common projects.
| Project | Size | Typical range* |
|---|---|---|
| Bedroom or office addition | 250 SF | $50,000 – $81,000 |
| Family room addition | 400 SF | $80,000 – $130,000 |
| Primary suite with bath | 500 SF | $137,500 – $212,500 |
| Second-story addition | 800 SF | $240,000 – $380,000 |
| ADU or in-law suite with kitchen | 600 SF | $150,000 – $240,000 |
*Ranges by type: simple rooms $200–$325/SF, in-law suites and ADUs $250–$400/SF, primary suites with a bath $275–$425/SF, second stories $300–$475/SF. Kitchens, baths and full basements push toward the top of each range. Your written proposal is based on a free on-site visit.
Second-story additions
Going up keeps your yard and avoids new foundation work, but it is the most technical addition. Before we price one, we confirm the existing walls and foundation can carry the new load, and plan the stair location so the first floor still works.
- Structural review of foundation, walls and framing
- New floor system, walls and roof tied to the existing house
- Temporary weather protection while the roof is open
- Stair, HVAC and plumbing routed through the first floor
- Exterior siding and roofline matched to the house
ADUs and in-law suites
ADU rules are set county by county and change over time, so the first step is checking what your zoning allows: lot size, setbacks, size limits, parking and utility connections. We confirm the rules for your lot before you pay for design.
- Attached suites with a separate entrance
- Detached backyard units
- Garage conversions and space over the garage
- Kitchenettes, full kitchens and accessible baths
Timeline
How long an addition takes
| Phase | What happens |
|---|---|
| Consult & feasibility | Site visit, zoning and setback check, rough budget |
| Design & engineering | Drawings and structural engineering through our partners |
| Permits | County review and approval |
| Foundation & framing | Footings, foundation, framing and roof tie-in |
| Rough-ins & inspections | Plumbing, electrical, HVAC and county inspections |
| Finishes | Insulation, drywall, trim, flooring, fixtures and paint |
| Walkthrough | Final inspection, punch list and warranty |
Design and permitting often take as long as construction. You get a target schedule with your proposal and weekly updates once work starts.
Related: Kitchen & bath remodeling · Basement finishing · Drywall & doors
How it works
Our 5-step process
- Free consultWe visit, measure, and talk through goals, timeline and budget.
- Written proposalItemized scope, price, schedule and a Maryland home improvement contract.
- Permits & scheduleWe pull permits and lock in your start date.
- BuildA clean, protected site and weekly updates until it’s done.
- Walkthrough & warrantyFinal walkthrough, punch list, and a 1-year workmanship warranty.