Factors that determine the cost of a sunroom


Sunroom interior

Your spouse has been talking incessantly about a friend’s new sunroom.  It has an airy, wide open space and great style, but mostly, it has light. Great views, comfortable furniture, and light, warm, bright light — light streaming in from the large windows, light from the gable end, light from the skylights above.  You visited their home, and your spouse is right:  the sunroom is bright, warm, and inviting.  Together you spent a relaxing, almost magical, afternoon in that room.  So now you want a your own sunroom.  But what does a sunroom cost?

Your friends wouldn’t tell you exactly what they spent.  It cost more than $60,000, but they wouldn’t tell you any more.  I can help you.

But first, let me ask you a question.  What does a new car cost?  “Well, that depends…”

Chevy SparkYou can buy a new Chevy Spark for under $12,000.  It’s seats four and gets 38 miles per gallon. But it looks a little cramped.

Red Ferrari Leferrari

On the other end, you could buy a Ferrari Laferrari for $1.3 M.  It seats two and gets to 120 mph in just 6.9 seconds.  And it looks fast, too.  (No one asks about its mpg.) See footnote.

That price range — $12,000 to $1,300,000 — is massive: over 10,000%.  What drives such a variation?  The Ferrari  is hand-made, looks cool, and I guess developing all that speed takes some fancy engineering.

Happily, sunroom prices do not vary that much, and the differences are more evident.

Before I identify the cost factors that drive sunroom prices, I need to clarify the subject.  I am ignoring the pre-fabricated metal DIY room kits you stick onto your house.  Sure, you can find a manufacturer who will ship you a “sunroom kit” for only $7,000.  You’ll receive boxes of parts, and realize there is “some assembly required” — like building the foundation, attaching the walls, installing the windows,… and how do you tie the roofs together?  You don’t want leaks.

Metal sunroom parts

Your sunroom kit

Here I address custom designed, site-built sunrooms that are integrated with and become part of your house.  The sunroom’s siding and trim and roof and eaves match your house, so it looks like it was always been there.

Carom sunroom, Bedford, MA

Six major factors drive the cost of a sunroom:

  1. Size.  A large sunroom costs more than a small sunroom, but the cost difference is not linear.  Increasing a 12′ x 12′ room to 24′  x 12′ doubles the floor and roof size, but may add only 33% to the walls and windows.
  2. Type.  You can build a simple sunroom without heat and enjoy it three seasons a year, perhaps using a space heater occasionally.  But to use it in winter and make it a four season sunroom, you’ll need to add heat and insulation and upgrade those single pane windows to insulated glass.  Your building code will dictate the insulation you need and how energy efficient your windows must be.
  3. Site Conditions.  A variety of exterior conditions can impact the cost.  You may have an existing porch or deck you can convert to a sunroom.  That could be a major advantage, if the structure is sound and you like the size.  To understand the feasibility of such an upgrade, see my blog article about converting a deck to a porch.  For a detailed explanation of the factors that affect The exterior terrain will determine the height of your room above grade;  higher is more costly, unless you need to excavate.  You will also need an access path to bring in machines and materials.  A dumpster can be cost effective, but it needs space.  Is there a stoop or stairs or another structure you’ll need to remove?
  4. House Conditions.  Where will the sunroom attach to your house?  A sidewall connection is generally easier than a roof-to-roof tie-in, but the location of windows (and vents) on the house wall can complicate a new roof and its pitch.  Access from the house can be interesting.  Do you have an existing door you could use?  You may be able to convert an existing window to a door, depending on its width.  Pipes, wires, and outlets in the wall will complicate that conversion.  You can cut an opening in a house wall and insert a door — but only if you understand how the wall is built, what is hidden in the wall, and what structural loads it supports.  Your home’s existing utilities can help or hinder construction.  Your new sunroom will need electricity for lights, outlets, etc., and your electric panel may or may not have enough additional capacity.  If you will heat the sunroom and your heating system has enough capacity, extending it into the sunroom may be fairly straight-forward.  If not, a system upgrade or a separate unit will add more cost.  Electric baseboard heat is independent and inexpensive to install, but more expensive to run.  Installing electric radiant heat under your finished floor is more expensive, but it surely feels great on bare feet.  Cooling your new room can be easy if you already have central A/C and the system has enough capacity.  Otherwise a small independent system may be appropriate.

Sunroom, Burlington, MA

  1. Features.  The configuration and features you choose for your room impact its cost, but at least you control your choices.  Unless you want a basement under your sunroom, a full foundation is not necessary.  A frost wall or, even less expensive, footing piers will suffice.  You can choose to have a flat ceiling or a cathedral ceiling that follows the roofline.  Cathedral ceilings are very popular in sunrooms because they increase space and can provide more light, but their construction is more complicated. The type, size, and quality of windows range widely, as does their price.  For even more light (and money), you can add skylights and/or gable glass.  The interior finish of a sunroom expresses its personality.  A room with rough paneling and exposed rafters will feel more rustic.  Bead-board or plaster walls and ceiling, and hardwood or tile floor will create a more formal room — and will cost more.
  2. The Company you choose.  Planning and building a sunroom is complicated;  it has many of the features of a complete house.  Be very careful which sunroom contractor you choose to design and build your new room.  The least expensive price likely carries the greatest risk.  I suggest you choose a company that has extensive experience designing and building sunrooms.  From the right company, you can expect professional designers who listen carefully to all your requirements and suggestions.  You should insist on full-color, 3 dimensional computer renderings of your project.

The days of flat, pencil sketches are long over.  Today computer graphics can show a sunroom on your home in near photographic quality.

Scaled 3-D rendering

Scaled 3-D rendering

Look at it from different angles, zoom in.  A skilled designer can show you how the sun will shine through your windows at any given time on any day of the year.  Change the room:  try larger windows, add gable glass, move the furniture around.  A sunroom is a major addition to your home, you need to see exactly how it looks from all angles before you commit those big dollars.

Building your sunroom requires the same thorough professionalism.  You need a sunroom builder who will draw detailed structural drawings, who will get the required permits, who will interact with the various town inspectors (so you don’t), who has skilled and experienced carpenters, and who knows and manages the needed sub-contractors.  Ask candidate companies to explain their design and construction process in detail.  Communication with you is critical.

Do not accept an estimated cost or a “price range.”  A company who understands exactly what you want and knows exactly how to build it can give you an exact price.  An exact, fixed price.

Sounds like a company who does all this will be expensive.  Actually, a company who does all this will save you money.  And headaches.  That company has studied your project thoroughly, and when it builds your sunroom, there will be no surprises.  A company who just estimates the cost does so because it has not studied your project thoroughly.  It does not understand all the details.  So it guesses at the cost.  And when it finally does understand everything — at the end of the project — guess what happens to that “cost estimate”?  It goes up.  As high the contractor wants – after all, it was only “an estimate.”

One final caution.  You could save considerable money if you design the sunroom yourself and if you manage construction yourself.  Really.  But do you have experience in residential construction?  Do you understand the building code and electrical codes?  Can you create all the structural drawings needed to apply for a building permit?  Can you calculate the structural path from the gable ridge down to the footings?  Are your stairs allowed to encroach into the setback?  Do you want to explain to the building inspector how your insulation meets the energy code?

The actual construction of a sunroom involves different tradesmen, often many: excavator, concrete installer, carpenter, electrician, HVAC installer, plumber, plasterer, finish carpenter, roofer,…. You can hire an experienced general contractor to build the room and manage all the sub-contractors.  He may seem more expensive initially.  Or you can be the general contractor yourself, and manage all the sub-contractors.  You can save money — if you have the time, knowledge, and experience needed.  Be very careful here, there are thousands of dollars at issue.  Can you explain structural drawings to a carpenter?  Do you know through which framing members an electrician can drill, where and how large?  The electrician is focused on running his wires efficiently;  he doesn’t care about the framing.   Will the flood lights interfere with the gutters?  How can the plumber install the baseboard heat before the blueboard?  When should the insulation be installed?  The list of issues seems endless.  The general contractor is responsible for all the issues — and for all the additional costs when conflicts arise, and subs have to make extra trips, and carpenters have to wait, and work has to be re-done.  For an inexperienced general contractor, those extra costs will mount quickly.  Do you want to be that general contractor?

A sunroom is a complicated project, and calculating its cost is complicated.  You’ve read about the major factors that impact its cost.  But how can you get some initial   estimate?  Remodeling Magazine has perhaps the best answer.  Each fall (for over 20 years) it researches and publishes a “Cost vs. Value Report” that lists the average cost of numerous home remodeling projects in various parts of the country, including the cost of a “Sunroom Addition”.  Click on that project name for a brief description, some simple 3-D drawings, and a construction cost in your part of the country.  Undoubtedly it is not exactly your sunroom, but it’s a start.

Footnote:  The most expensive production car might be the Lamborghini Veneno: for $4.5 million you get only two seats, but 0 to 60 mph in 2.8 seconds and top speeds over 220 mph.  I did not include it above because only twelve are being made, and all are spoken for.  Sorry.

Lamborghini Veneno

Lamborghini Veneno

We at Archadeck of Suburban Boston offer professional design and build services for clients west and north of Boston.  Over the past 23 years we have designed and built over 800 projects, including 80 sunrooms.  We have enhanced the depth of our expertise by limiting our work to decks, porches, sunrooms, and patios.  To view some of these projects, visit our website.  To learn how we treat our clients, check our ratings on Angie’s List or read about us in an article in Remodeling magazine.  For a free design consultation and a relaxed and rewarding experience, contact us via e-mail, subboston@archadeck.net or by phone, 781-273-3500.

© 2013 Advantage Design & Constr., Inc.

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Categories: 3 Season Porch, Porch, Sunroom, Sunroom costTags: , , , , , , , , ,

2 comments

  1. Sunrooms are great. We even saw some sun closets not quite a room on the top of entrance porches in Ireland, looked just big enough for 2 chairs but they were all over one area in the west of Ireland.

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