Most sunroom additions cost between $22,000 and $75,000, with a national average of about $47,000, according to HomeAdvisor’s cost data. A simple three-season room sits at the lower end of that range. A fully insulated four-season room or a glass solarium sits at the top. Screening in a porch you already have can cost just a few thousand dollars.
Where your project lands depends on the type of room, its size, what you’re building on, and the finishes you choose. The good news is that you don’t have to pay for it all at once: financing can spread the cost into manageable monthly payments.
This guide covers what each type of sunroom costs, the price per square foot, what a 12×12 room runs, the factors that push a quote up or down, ways to keep costs in check, and how financing works.
Sunroom Addition Cost at a Glance
The type of room drives the price more than anything else. These are national ranges from the cost guides named in the last column.
|
Type of room |
Typical cost |
What you get |
Source |
|---|---|---|---|
|
Screening an existing porch |
$2,000–$4,000 (average about $2,800) |
Screens fitted to a porch that already has a roof and floor |
|
|
Porch enclosure (three-season) |
$7,000–$55,000 |
An existing porch closed in with windows or panels |
|
|
Three-season sunroom |
$10,000–$40,000 |
Glass walls, not tied into the home’s heating and cooling |
|
|
Four-season sunroom |
$25,000–$80,000+ |
Insulated walls, roof and glass, heated and cooled for year-round use |
Bob Vila; HomeAdvisor puts high-end rooms up to $120,000 |
|
Solarium |
$30,000–$75,000 |
Glass overhead as well as on the sides |
|
|
Prefab sunroom kit |
$6,000–$40,000 |
The kit only, before foundation, labor and permits |
You may also hear a sunroom called a Florida room. It’s the same thing, at the same prices.
If you’re deciding between the two most popular options, our guide to choosing between a 3-season and 4-season sunroom compares how each one handles a Delaware winter.
Sunroom Cost Per Square Foot
For a custom-built sunroom, expect roughly $150 to $300 per square foot, according to HomeAdvisor. Prefab rooms can start closer to $100 per square foot, though the kit price leaves out a lot of the work.
Where you build matters too. Turning an existing porch, deck or patio into a sunroom usually costs less per square foot than building from the ground up, because the floor and sometimes the roof are already there. One cost guide puts conversions at $80 to $200 per square foot and full additions at $130 to $300 (Fixr, last updated in 2022).
Treat any per-square-foot figure as a starting point, not a quote. Small rooms often cost more per square foot than large ones, because the doors, the connection to your house and the permit cost about the same whatever the size.
How Much Does a 12×12 Sunroom Cost?
A 12×12 sunroom (144 square feet) typically costs $18,000 to $42,000 as a three-season room and $30,000 to $60,000 as a four-season room, according to Block Renovation’s 12×12 cost guide. HomeAdvisor’s per-square-foot range lands in the same place, at $21,600 to $43,200 for a custom room.
Here’s how the main options work out for a 144-square-foot space, with the math shown so you can check it:
|
12×12 option |
Rate used |
Estimated cost |
|---|---|---|
|
Screening an existing porch |
$5–$20 per sq ft (HomeAdvisor) |
$720–$2,880 |
|
New screened porch with a roof |
$25–$120 per sq ft (HomeAdvisor) |
$3,600–$17,280 |
|
Three-season sunroom |
Block Renovation 12×12 guide |
$18,000–$42,000 |
|
Four-season sunroom |
Block Renovation 12×12 guide |
$30,000–$60,000 |
|
Custom sunroom, any type |
$150–$300 per sq ft (HomeAdvisor) |
$21,600–$43,200 |
For a sense of scale, a 12×12 room holds a dining table for four, or a sofa and a pair of chairs. When you collect quotes, ask every contractor to price the same size and room type so you’re comparing like with like.
Patio and Porch Enclosure Costs
If you already have a covered porch, deck or patio, enclosing it is often the most affordable route to sunroom-style space. Screening a porch that already has a roof averages about $2,800 (HomeAdvisor). Closing one in with windows for three-season use runs $7,000 to $55,000 (Angi). The wide range comes down to the size of the space, whether you choose screens, vinyl panels or glass, and how much repair the existing structure needs.
That last point is the one to check first. Glass walls and a solid roof weigh far more than a railing, so an older deck may need new footings or extra framing before it can carry an enclosure. On the coast, it’s also worth checking the deck’s fasteners and hardware for rust, since salt air wears them out faster. A good contractor looks at the structure before giving you a price, not after.
If your porch or deck isn’t up to the job, replacing it is often simpler than patching it. We also build decks, so the deck and the enclosure can be planned as one project.
Building on the Delaware Coast? Extra Costs to Plan For
National cost guides are written with a typical inland suburb in mind. If your home is near the water, as so many are in Sussex County, Delaware, plan for these as well:
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Flood zones. Many coastal lots, from the beach towns to the land around the Inland Bays, sit in FEMA flood zones. A sunroom there may need a raised floor or a different foundation. Under Delaware’s floodplain rules, if a project costs 50% or more of the home’s market value (not counting the land), the whole house must be brought up to current flood standards (DNREC). A typical sunroom won’t reach that line on its own, but a large addition combined with other renovations can, so check before you finalize plans. You can look up your flood zone on FEMA’s Flood Map Service Center.
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Salt air and wind. Near the ocean, aluminum framing and corrosion-resistant hardware are worth the extra cost, and open or waterfront lots may need sturdier glass and framing. These choices cost more up front but less than replacing rusted parts a few years later.
Other Things That Move the Price
Beyond room type and size, these are the line items that most often widen or narrow a quote:
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Foundation and site work. A new foundation runs about $1,000 to $6,000 (Bob Vila), and clearing or grading the site adds more. Building on a sound existing deck or slab can avoid some of this.
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Glass. Double- or triple-pane glass with low-E coatings costs more than single-pane, but it’s what keeps the room comfortable in both July and January.
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Heating and cooling. A four-season room needs it. A ductless mini-split is a common choice, at roughly $2,000 to $14,500 depending on the system (Bob Vila).
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Electrical. Outlets, lighting and a ceiling fan add cost, and they’re far easier to plan in from the start than to add later.
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The roof connection. Tying a sunroom roof into your existing roofline takes more work than a simple flat roof. Unusual shapes cost more too: Block Renovation estimates custom shapes add 20% to 40%.
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Labor. Labor typically makes up 40% to 60% of the total, according to HomeAdvisor.
DIY Sunroom Kits vs. Professional Installation
Prefab kits look like a bargain at $6,000 to $40,000 (HomeAdvisor), but that price covers the kit, not the finished room. You still need a foundation, a building permit, inspections, and someone to connect the room to your house without leaks. With labor making up 40% to 60% of a typical project, the savings shrink once those costs are added back in.
On the coast there’s another question: whether the kit’s framing, hardware and glass suit salt air, wind and flood requirements. A kit designed for a mild inland climate may not. If you’re considering one, ask the manufacturer for its wind ratings and hardware specifications, and check with the county before you buy.
Ways to Keep Sunroom Costs Down
A sunroom doesn’t have to be the most expensive version to be worth it. A few ways to build one on a budget:
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Start with what you have. Enclosing an existing covered porch or a sound deck usually costs less per square foot than building new.
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Match the room to how you’ll use it. If you mainly want spring, summer and fall, a three-season room costs far less than a four-season one, and Delaware’s relatively mild winters stretch its useful season.
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Keep the shape simple. A rectangle with a straightforward roof costs less than a custom shape.
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Compare quotes properly. Ask each contractor to price the same size, room type and glass, so the lowest number isn’t simply the one that leaves things out.
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Spread the cost. Financing options can let you build the room you actually want instead of settling for less. More on that below.
Sunroom Financing Options
A sunroom is a big purchase, and most people don’t want to pay for it all at once. Financing lets you spread the cost into monthly payments, so you can build the room you’ll actually use rather than the one that fits this month’s budget. It can be the difference between a three-season room and the four-season room you really wanted, or between doing the project now and putting it off another year.
Coastline offers financing through Service Finance Company, LLC. You can start an application online from our financing page, and the approval process is quick. We’re happy to talk it through during your free estimate, too.
Whichever lender you use, a few questions help you compare plans fairly:
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What’s the interest rate, and is there a promotional period? If so, what happens when it ends?
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How long is the term, and what will the total cost be over the life of the loan, not just the monthly payment?
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Are there fees for applying, or penalties for paying it off early?
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When do payments start, before, during or after installation?
A simple order of steps works best: get a detailed quote first, so you know the real number, then choose the financing that fits it.
When to Start Planning Your Sunroom
If you’d like to be using a new sunroom by late spring or summer, fall and winter are the time to start. Design, quotes and permit review all take time, and HomeAdvisor notes that permit processing alone often takes four to eight weeks. Planning now means your design and permit can be in place before spring, when many homeowners try to book outdoor projects at once.
Timing matters even more for second homes and rentals in Rehoboth Beach, Bethany Beach and Ocean City. A sunroom finished before Memorial Day adds to the season. One still under construction in June gets in the way of it.
Delaware’s relatively mild winters help too. Unlike in much of the northern U.S., building here in winter is often possible when the weather cooperates, so planning early doesn’t have to mean a long wait.
Sunroom Cost FAQs
What is the average cost of a sunroom addition? Nationally, most sunroom additions cost $22,000 to $75,000, with an average of about $47,000 (HomeAdvisor). Three-season rooms fall toward the lower end, and four-season rooms and solariums toward the top.
How much does a 12×12 sunroom cost? About $18,000 to $42,000 for a three-season room and $30,000 to $60,000 for a four-season room (Block Renovation). Screening an existing 12×12 porch can cost under $3,000.
Is a sunroom less expensive than a traditional room addition? A three-season room usually is, because it skips the insulation, heating and cooling, and much of the interior finishing a regular addition needs. A four-season sunroom is built to similar standards as an addition, so the price gap narrows.
Do I need a permit for a sunroom? In most cases, yes. A sunroom that attaches to your home and changes its footprint usually needs a building permit. In Sussex County, the fees for a small sunroom add up to only a few hundred dollars, and homes in flood zones may face extra requirements. Your contractor should handle the application for you.
Does a sunroom add value to a home? A sunroom adds usable, light-filled space, which buyers in coastal markets tend to value. A four-season room that’s heated and cooled is more likely to be treated as living space than a three-season room or a screened porch.
Can I finance a sunroom? Yes. Coastline offers financing through Service Finance Company, LLC, so you can spread the cost of a sunroom or porch enclosure into monthly payments. You can apply online from our financing page or ask about it during your free estimate.
Planning a Sunroom in Sussex County? Talk to a Local Team
National averages are a useful starting point, but your price depends on your home, your lot and how you want to use the room. Coastline Sunrooms & Awnings is a family-owned company based in Selbyville, and our team brings more than 30 years of experience in outdoor living along the Delaware and Maryland coast. As an authorized TEMO dealer, we design and build three-season rooms, four-season sunrooms and porch enclosures, and we handle the permit process for you.
We’ll visit your home, look at your porch, deck or yard, check what your lot requires, and give you a clear, no-obligation quote.
Call (443) 844-8194 or request your free estimate online.