sunroom cost to build

The average sunroom cost to build lands between $20,000 and $70,000 in 2025, with most homeowners spending roughly $35,000 for a standard 12-by-12-foot three-season room. That’s a wide range because a sunroom is not one product — it can be a simple prefab kit screwed onto an existing deck or a fully insulated, climate-controlled four-season…