Most sunroom additions in Mandeville, LA range from $25,000 to $100,000, depending on whether you build a three-season room or a fully conditioned four-season addition tied into your home’s HVAC system.
If you’re picturing a bright, comfortable room off the back of your house — somewhere to sit with coffee, watch the yard, or just get out of a closed-off living room — a sunroom addition is one of the most direct ways to get there. But “sunroom” covers a wide range of actual construction, and that’s exactly why the price range is wide too. A screened-in porch conversion and a fully conditioned four-season addition with a new foundation are both called sunrooms, and they can be $60,000 apart.
This guide breaks down what drives that cost in Mandeville and the greater Northshore specifically, and walks through a real four-season sunroom addition we recently completed here — what it included, what it cost, and why we made the choices we did.
Sunroom Addition Costs by Type
Three-Season Room or Screened Porch Conversion — $20,000 to $40,000
Built on an existing slab or deck footprint, with single-pane or basic double-pane glass and no dedicated heating or cooling. Comfortable spring through fall, but not built for a Louisiana summer or a cold snap.
Four-Season Sunroom, Standard Finishes — $45,000 to $70,000
Fully insulated and conditioned, tied into (or supplementing) your existing A/C, with true double-pane windows built to hold up to Louisiana humidity. This is the range most Mandeville homeowners land in for a true year-round room.
Four-Season Addition, Premium Finishes — $70,000 to $100,000+
A new foundation rather than an existing slab, hurricane-impact glass, a gas fireplace, upgraded flooring, and roofing built to handle a complex tie-in to the existing house. This is where full custom additions land — see our real Mandeville project below.
What Actually Drives the Cost
Foundation. Building on an existing patio slab or deck footprint is far cheaper than pouring a new foundation. If your existing slab isn’t sized, sloped, or structurally sound for a conditioned room, that’s usually the single biggest line item on the estimate.
Roofline complexity. A simple lean-to roof tying into a straight wall is the easiest and cheapest tie-in. Homes with more complex rooflines — dormers, multiple pitches, chimneys nearby — sometimes call for a different roofing material than the rest of the house just to handle the tie-in cleanly and shed water and debris properly. That’s a material decision worth discussing with your contractor rather than assuming you’ll match the existing shingle everywhere.
HVAC. Tying into your existing A/C system — after confirming it has the capacity to serve the added square footage — is almost always cheaper than adding a standalone mini-split or ductwork run. This is a step worth having verified before signing a contract, not assumed.
Windows. In Louisiana, hurricane-impact glass costs more upfront than standard double-pane, but for a room that’s largely windows, it’s worth pricing out — it protects the investment and, in many parishes, can affect your insurance and permitting.
Finish level. A gas fireplace, luxury vinyl plank or hardwood flooring, and interior trim details add cost but are also what turn a functional add-on into a room people actually spend time in.
From a Worn-Out Deck to a Four-Season Sunroom
We recently completed a ~400 sq ft four-season sunroom addition in Mandeville for $70,000 over 6 weeks — full demolition of an old deck, new foundation, framing tied into a complex roofline (we used a metal standing seam roof instead of matching shingle, since it handled the tie-in and shed debris better), a gas fireplace, and hurricane-impact glass windows. The homeowners wanted a comfortable, year-round spot to watch the birds in their backyard — the room delivers exactly that.
Building a Sunroom on the Northshore
Mandeville’s humidity and proximity to Lake Pontchartrain mean materials matter more here than in a drier climate — proper flashing and waterproofing where the addition ties into the existing roof and walls is what keeps a beautiful new room from becoming a moisture problem a few years down the line. We handle all permitting through the City of Mandeville and St. Tammany Parish as part of every addition, including any hurricane-code requirements for glass and structural connections.
Common Questions
What’s the difference between a three-season and four-season sunroom?
A three-season room has basic glass and no dedicated heating or cooling — comfortable spring through fall, but not built for summer heat or winter cold. A four-season room is fully insulated, uses true double-pane glass, and is tied into heating and cooling, making it usable year-round like any other room in the house.
Do I need a new foundation, or can I build on my existing deck or patio?
It depends on the condition and size of what’s already there. An existing concrete patio slab in good condition can sometimes be built on directly. Wood decks and undersized or cracked slabs typically need to be removed and replaced with a proper foundation designed for a conditioned room.
Can my current A/C system handle a new sunroom addition?
Sometimes — it depends on your existing system’s capacity and the size of the addition. We check this before recommending an approach. If the existing system has room to spare, tying in is usually more cost-effective than adding a separate unit.
Do sunroom windows in Louisiana need to be hurricane-impact rated?
Requirements vary by parish and by how the room is classified, so it’s worth confirming for your specific address. Many homeowners choose hurricane-impact glass for a sunroom regardless, since the room is largely windows and impact glass adds protection and can affect insurance.
How long does a sunroom addition typically take?
Most four-season sunroom additions run 5 to 8 weeks from demolition to final walkthrough, depending on the scope, whether a new foundation is required, and material lead times. A recent Mandeville project we completed — a ~400 sq ft four-season addition — took 6 weeks.
Thinking about a bigger addition than a sunroom? See our full home addition cost guide, or explore our Mandeville home addition services to see what’s included.
Ready to Talk Through Your Sunroom?
Every home and every roofline is different. The best way to get an accurate number is a walkthrough — we’ll give you a detailed, thorough estimate before anything is scheduled.