Cost guide
Sunroom Addition Cost in 2026
A sunroom adds bright living space without the expense of a full room addition. Size, foundation and how you heat it drive the price.
Sunroom cost by size
| Scenario | Estimated range | Per sq ft |
|---|---|---|
| Small sunroom (150 sq ft)Slab foundation, standard finishes | $29,600 – $72,900 | $197–$486 |
| Mid-size sunroom (250 sq ft)Slab foundation, standard finishes | $44,300 – $103,500 | $177–$414 |
| Large sunroom (350 sq ft)Crawlspace foundation, high-end finishes | $74,900 – $167,300 | $214–$478 |
Estimates at national-average pricing, calculated with our own pricing engine and reviewed September 2026. Change the inputs in the calculator to price your exact project.
Three-season vs four-season
Three-season sunroom
No heating or cooling, lighter framing and often single-pane or basic glass. Comfortable from spring through fall, and the lowest-cost option.
Four-season sunroom
Insulated walls and roof, insulated glass and heating and cooling, so it is usable year-round. It costs more and behaves like any other room addition.
Our calculator prices a sunroom addition with standard insulation and heating. For a three-season room, turn off Extend heating & cooling in the systems step.
Frequently asked questions
How much does a sunroom addition cost?
It depends on size, foundation and whether it is three-season or four-season. A small three-season room costs far less than a large four-season one with insulation, heating and a full foundation. The table above shows current ranges by size.
Is a sunroom a good investment?
Sunrooms typically return about 50–70% of their cost at resale. They add living space without the expense of a full room addition.
How long does it take to build a sunroom?
A prefab sunroom kit can be installed in 2–4 weeks. Custom-built sunrooms take 6–12 weeks, including foundation, framing and finishing.
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