Home Addition Cost · 800 Sq Ft · 2026

An 800-square-foot addition is substantial — enough for a full primary suite plus a sitting room, a large great-room-and-kitchen expansion, or a complete in-law suite. Here’s what it costs to build one in NJ and PA in 2026.

$200,000 – $320,000A fully permitted 800 sq ft addition in South Jersey and the PA Main Line typically runs in this range in 2026. Simple single-story living space sits lower; a suite with a bath, a kitchen, or a two-story build pushes toward the top.

800 Sq Ft Addition Cost by Scenario

ScenarioTypical 2026 cost
Single-story living space, no plumbing$200,000 – $240,000
Single-story with a full bath$230,000 – $270,000
Full in-law suite or primary suite (bed, bath, kitchenette)$260,000 – $300,000
Two-story addition$285,000 – $320,000+

All-in ranges covering design, permits, structure, mechanicals, and finishes — roughly $250 to $400+ per square foot depending on complexity and what the space contains.

What Moves an 800 Sq Ft Addition’s Price

Kitchens and baths. At this size you’re often adding a suite or a great-room-plus-kitchen. Every plumbed and gas-fed space — full bath, kitchenette, kitchen — adds meaningful cost over dry living space.

Single vs. two story. An 800 sq ft footprint is a large single-story addition; splitting it across two floors changes the foundation, structural, and roofing math. We price both where the lot allows.

Finish level. At six figures, finish selections — flooring, cabinetry, tile, trim — swing the total more than most homeowners expect. We lock selections before the contract so the number holds.

Related reading: Compare with our 500 sq ft addition cost guide, or start with the main home addition cost guide for the full breakdown by size. Serving South Jersey home additions and the PA Main Line.

800 Sq Ft Addition FAQs

How much does an 800 sq ft addition cost per square foot?

Roughly $250 to $400+ per square foot all-in in NJ and PA. Dry living space sits at the lower end; suites with baths or kitchens, and two-story builds, run higher.

Is 800 square feet enough for an in-law suite?

Yes — 800 sq ft comfortably fits a full in-law suite with a bedroom, full bath, sitting area, and a kitchenette, often with a private entrance. It’s one of the most popular uses for an addition this size.

How long does an 800 sq ft addition take?

Plan on a project measured in several months from design to a closed permit. Design and permitting happen before construction, and the build itself proceeds in sequence with township inspections at each phase.

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