Decide Addition Type: Up, Out, or Bump-Out?
Each addition type has different costs, structural requirements, and impacts on your home. The right choice depends on your lot, existing structure, budget, and what you're trying to accomplish.
Quick Comparison
Second Story (Up)
$200-400/sq ft
Ground Level (Out)
$150-300/sq ft
Bump-Out
$150-350/sq ft
Addition Types Compared
Second Story Addition (Building Up)
Adding a full or partial second floor to a single-story home. The most complex option but preserves your yard.
Advantages
- • Doesn't reduce yard space
- • Often adds more value per sq ft
- • Better views from new rooms
- • More dramatic transformation
- • Works on small lots
Disadvantages
- • Requires structural engineering
- • Foundation may need reinforcement
- • More expensive per sq ft
- • Longer construction time
- • More disruptive during construction
- • Height limits may restrict
Best for: Small lots where expanding out isn't possible, homes with strong foundations, or when preserving yard space is a priority.
Cost Breakdown
Structural engineering
$3,000 - $8,000
Foundation reinforcement
$10,000 - $30,000+
Construction per sq ft
$200 - $400
Typical timeline
4 - 8 months
Ground Level Addition (Building Out)
Extending your home's footprint at ground level. Requires new foundation but avoids structural changes to existing home.
Advantages
- • Easier structurally (new foundation)
- • Less expensive per sq ft
- • Can often stay in home during construction
- • Easier to match existing roofline
- • More flexibility in layout
Disadvantages
- • Reduces yard/outdoor space
- • Requires adequate setbacks
- • May hit lot coverage limits
- • Excavation and foundation work
- • Landscaping disruption
Best for: Larger lots with room to expand, homes where foundation can't support second story, or when accessibility matters (no stairs).
Cost Breakdown
Foundation
$8,000 - $20,000
Excavation
$2,000 - $6,000
Construction per sq ft
$150 - $300
Typical timeline
3 - 6 months
Bump-Out Addition (Small Extension)
A small extension (typically 2-8 feet) that expands an existing room. Often used to enlarge kitchens, bathrooms, or create a breakfast nook.
Advantages
- • Lowest total cost
- • Simplest permits (sometimes none)
- • Fastest construction (1-4 weeks)
- • Can cantilever (no foundation needed)
- • Minimal yard impact
- • Often stays in home during work
Disadvantages
- • Limited space gain (20-100 sq ft)
- • Can't create new rooms
- • Higher cost per sq ft
- • Design constraints
- • May look odd if not designed well
Best for: When you just need a little more space in a specific room—expanding a cramped kitchen, adding a master bath, or creating a window seat/reading nook.
Cost Breakdown
Cantilevered (no foundation)
$5,000 - $15,000
With foundation
$15,000 - $40,000
Cost per sq ft
$150 - $350
Typical timeline
1 - 4 weeks
How to Decide
Answer these questions to narrow down the best addition type for your situation:
How much space do you need?
- • 20-100 sq ft: Bump-out is usually best
- • 200-500 sq ft: Ground level or second story
- • 500+ sq ft: Ground level or second story (or combination)
What's your lot situation?
- • Small lot / tight setbacks: Second story likely only option
- • Large lot with yard space: Ground level gives most flexibility
- • At or near lot coverage limit: Second story or bump-out
What's your home's structure like?
- • Strong foundation, good condition: Second story possible
- • Older/weaker foundation: Ground level or bump-out safer
- • Ranch/single-story: Either works, depends on goals
What's your budget?
- • Under $30,000: Bump-out only
- • $50,000-$150,000: Ground level addition
- • $100,000-$300,000+: Second story or large ground level
Frequently Asked Questions
Which addition type adds the most value?
Second-story additions often add more value because they increase living space without reducing yard size. However, ROI depends heavily on your market—in some areas, single-story homes are preferred. A local real estate agent can advise on what buyers in your area want.
Can I do a combination of addition types?
Absolutely. Many projects combine a small ground-level addition with a second story above it. This maximizes space while requiring only one new foundation. Discuss hybrid options with your architect.
How do I know if my foundation can support a second story?
You need a structural engineer to assess this ($500-$1,500). They'll examine your foundation type, condition, soil conditions, and existing load paths. Don't assume either way—get professional evaluation before committing to plans.
Ready for the Next Step?
Once you have a general idea of addition type, the next step is evaluating whether your existing utilities can handle the expanded space.