How Much Does A Composite Deck Cost?

by Rick Wedding | Last Updated: March 24, 2021

Have you heard the rumors that say composite decks are expensive? Well, the rumors are true. But it’s all relative, what’s expensive to one person is not expensive to another. The question remains, how much will it cost you and does the investment make sense?

How much will a composite deck cost? Of course, many variables will affect the final price of your composite deck, but I am giving you the basic formulas to estimate your new deck.

Before we dive in, ask yourself these two questions.

Are you building the deck yourself?

Are you hiring a deck contractor?

DIY composite deck build

Are you handy or have a friend that has built their deck? Before you answer this to quickly, I must caution you; there is a big difference between building a treated and composite deck. A treated deck leaves a lot of room for error. If you do mess up with treated the costs to fix are minimal. Composite, on the other hand, can cost hundreds or thousands if you make mistakes. If I haven’t scared you off, then go ahead and get the sketch of your deck and figure up the square footage.

Take the square footage of your deck and multiply that number by $30 – $40. The range in price will account for different types of deck and rail. If you tend to have expensive taste, then multiply by the higher dollar amount. This figure will give you the material cost for concrete, framing, composite deck surface and composite railing. This number will not include the stairs or stair railing. When using the example sketch above, you will find the cost to be $11,200.

Stairs must be estimated separately, and you will need to know the number of stair treads required for your project. If you need help figuring the number of stair treads visit this stair calculator on I have added an image below to show you how I used the calculator for the example deck. Once you have determined the number of stair treads, just multiply that number by $210 per stair riser. This dollar amount will cover the lumber, hardware, composite decking, risers, fascia, and composite railing for your stairs. The example deck above has 8 risers for the steps. If you take 8 x $210, you arrive at $1680.

Now just take the two numbers from above and add them together. This is the approximate material cost for your project. When using our example above (and using the $30 square footage figure), the cost for all materials is $11,280.

Is there anything that can throw the formula off?

  1. I based this formula on using products like Trex, Timbertech, Azek, Fiberon or Dekorators composite decking. If you are looking at a less expensive alternative, then the formula won’t work.
  2. This formula is based on your deck height being no more than five feet off the ground. When using a longer 6×6 post, you will see a slightly higher per square foot dollar amount.
  3. The formula also was anticipating the deck being fastened to your home by a ledger board and joist hangers. If you are opposed to attaching the deck to your home, you will require more concrete, posts, beams and hardware. Not connecting to your home will result in a higher cost per square foot.

So how much will a professional charge me?

Take the square footage of your flat deck area with no stairs. In the sketch above the 16×20 deck is 320 square feet. A professional deck contractor in the Cincinnati market will charge between $65 and $75 per square foot. So from our example above you take 320 square feet times $65. This deck would run approximately $20,800. Once again that would include the concrete, framing, hardware, deck surface and level railing. It does not include the stairs or stair railing. The is not an exact science and is to only provide you with an idea of what a composite deck will cost by having it built professionally. Some variables could lower or higher the total square foot pricing.

We determined from the online calculator that the stairs on our example above would require eight risers. To find out what the stairs and stair railing will cost, just take 8 X $275 for a total of $2200. This figure will cover the labor and material for your stairs.

Based on the formula and adding the stairs, you could expect to pay between $20,800 and $26,200 for a 16×20 composite deck.

What other costs should I consider?

Rick Wedding is the founder of Building Supply Guy and has been in the building materials industry since 1987. Since then, his mission is to make selecting products for your home easy for everyone. And each year, he continues to help more people with choosing the best products and services for their homes.