Home Addition Checklist

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Feasibility

Assess lot boundaries and setbacks

Review your property survey to understand where you can legally build.

Research local zoning requirements

Contact your planning department about lot coverage, height, and FAR limits.

Decide addition type

Up (second story), out (ground level), or bump-out (small extension)?

Evaluate existing utilities

Can your electrical panel, HVAC, and plumbing handle the new space?

Determine structural feasibility

Will your foundation and walls support a second story? Do you need underpinning?

Design

Hire an architect or designer

Additions require professional design to integrate with existing structure.

Design roof tie-in strategy

New roof must integrate seamlessly with existing structure and match aesthetics.

Plan interior flow and circulation

How will the addition connect to existing rooms? Hallway? Open concept?

Match exterior materials and style

Siding, trim, windows, and roof should blend with or complement existing home.

Obtain structural engineering plans

Engineer must design foundation, framing, and beam specifications.

Budget

Calculate realistic cost per square foot

Home additions typically cost $150-400/sq ft depending on complexity and finish level.

Factor in soft costs

Design fees, permits, engineering, and inspections add 15-25% to construction costs.

Explore home equity options

HELOC or home equity loan are common ways to finance additions.

Consider construction loan

For major additions, a construction-to-permanent loan may offer better rates.

Build 20% contingency buffer

Every addition has surprises - rotted sills, code upgrades, scope changes.

Permits

Interview 3-5 general contractors

Get detailed bids including timeline, payment schedule, and warranty.

Verify contractor licensing and insurance

Confirm general contractor license, general liability, and workers comp coverage.

Apply for building permit

Submit architectural plans, engineering drawings, and site plan to building department.

Obtain structural and electrical permits

Separate permits often required for structural changes and electrical work.

Get HOA or design review approval

If you have an HOA, get written approval before starting. Can take 30-60 days.

Schedule pre-construction meeting

Walk through plans with contractor to align on expectations and logistics.

Site Prep

Order updated property survey

Ensure stake out is accurate and addition stays within setbacks.

Call 811 for utility location

Mandatory free service marks underground electric, gas, water, sewer, and cable.

Excavate foundation area

Dig to depth specified in engineering plans, typically 42-48 inches below grade.

Install tree protection fencing

Protect root zones of trees you want to keep - damage kills trees slowly.

Set up construction fencing/barriers

Protect landscaping, create safe work zone, and keep kids/pets out.

Foundation

Pour foundation footings

Concrete base that supports foundation walls, must be below frost line.

Build foundation walls

Poured concrete or block walls that tie into existing foundation.

Frame walls and install beams

Erect wall studs, install engineered beams, and frame floor system.

Frame roof and create tie-in

Extend or connect new roof to existing, matching pitch and overhang.

Install sheathing and weather barrier

OSB/plywood sheathing, house wrap, and temporary roof protection.

Integration

Connect to existing structure

Open walls between old and new space, install beams if removing load-bearing walls.

Match exterior siding and trim

Blend new siding with existing, often requiring whole-side replacement for seamless look.

Install roofing and blend with existing

Shingle new roof section, flash intersection, match color and style.

Install windows and exterior doors

Match window style, grille pattern, and trim to existing home.

Match interior floor heights

Ensure seamless transition between old and new spaces, adjusting framing if needed.

Systems

Extend electrical to new space

Run new circuits from panel, add outlets, switches, and overhead lighting.

Run plumbing for bathrooms

If adding bathroom, run supply and drain lines to new space.

Extend HVAC system

Add ductwork, registers, and possibly new zone or system.

Install insulation

Meet or exceed code minimums, pay attention to air sealing.

Rough in smart home/networking

Run Cat6 for hardwired networking, consider whole-home audio, cameras.

Interior

Hang and finish drywall

Install drywall, tape seams, apply joint compound, sand smooth.

Install flooring

Coordinate flooring to blend with existing adjacent spaces.

Install baseboards and trim

Match existing trim profile and paint to blend old and new spaces.

Paint walls and ceilings

Prime and paint all new drywall, consider painting adjacent rooms for cohesive look.

Install interior doors and hardware

Match door style to existing home, consider upgrading hardware throughout.

Install bathroom fixtures

Toilet, vanity, shower/tub, tile work, and accessories.

Final

Blend old and new spaces visually

Step back and look at flow, color, lighting, and furniture arrangement.

Restore and regrade landscaping

Fix damage from construction, ensure proper drainage away from foundation.

Complete final inspection

Building department does final walkthrough to verify code compliance and issue CO.

Complete contractor punch list

Walk through with contractor to identify any incomplete or incorrect work.

Obtain warranties and documentation

Collect all warranties, permits, plans, and receipts for future reference.

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