How-To

Building a Rooftop Deck: Costs and Materials

 A rooftop deck is a great way to create a useful outdoor area with limited space. Learn about the costs and materials needed to build a rooftop deck with Trex.

March 29, 2022
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HGTV Dream Home 2021 in Newport, RI

Imagine watching the sun set with a perfect view of the ocean or hosting a party under the stars while the city teems with energy beneath you. A rooftop deck or roof deck patio can add a view and value to your property, while making the most of unused square footage for entertaining, dining and relaxing. By some estimates, the return on investment at resale for a rooftop deck can be as much as 150 percent.

At the same time, you must count the cost to add a rooftop deck, also referred to as a “floating” deck because it is usually placed on top of a roof. Overall, a rooftop deck requires some different materials and techniques than a standard backyard deck, especially as it will endure more of the elements and be dependent on your roof structure.

Necessary Roof Decking Materials

Not all materials usually used for a traditional deck or patio will work on a roof. Some roof decking material options are too heavy for the current structure. For example, you won’t be able to add heavy wood framing or a hot tub without assessing the ability for your structure to hold that additional weight. Always consult with an experienced builder upfront to assess what’s possible, and have a structural engineer approve the project.

The roof decking materials will require some sort of substructure to attach the decking boards to the roof – these are typically called sleepers and are made from pressure-treated wood or aluminum framing. 

Composite Decking Board

Next, you’ll need decking boards over the sleepers. Carefully choose your decking board material as you would for a regular deck.  Boards made from pressure-treated lumber will eventually split, crack and warp in this harsh environment, even with regular sealing and staining. A high-quality composite rooftop decking board is more durable and requires less maintenance.

Railing

To top off the deck, you’ll want to install a complementary railing to ensure your deck is safe for you, your family and friends. While you have many choices for colors and materials, you almost certainly must have a railing. The International Residential Code (IRC) requires any deck higher than 30 inches above the ground to have railings measuring at least 36 inches in height. In some jurisdictions, 42” rail heights are required. Check with your local building department. The space between individual balusters should be less than 4 inches, and the space between the bottom of the railing and the top of the deck surface also should be no more than 4 inches. 

Cost to Build a Rooftop Deck

You can expect rooftop deck costs to more than likely run anywhere between $25,000 and $75,000 depending on materials, size and amenities such as an outdoor kitchen, entertainment system or bar. You might also opt to create a cover for the deck, so you can enjoy it in all types of weather, but that will also add to the overall cost to build a rooftop deck. Structural engineering may reveal that you need an enormous amount of additional support to carry the load of all the new things you’ve added to the roof, such as outdoor kitchen, entertainment system or bar.

Necessary Permits

While different states will have different requirements, you will almost certainly need a building permit. When calculating rooftop deck costs, include the fees associated with these permits. Ask your builder or local building department what the local requirements are. It is also advisable to research any zoning restrictions or covenants, conditions and restrictions of your local homeowners association or community association.   

Size

Obviously, the size of your deck will influence its cost, as the larger the deck, the bigger the final price. This is also true because you may need to add additional supports for your roof. Enlist a structural engineer to check the capacity for your roof. 

HGTV Dream Home 2021 in Newport, RI

Cost Considerations

Once you determine the size of your deck, you can calculate the cost of the decking materials with an online calculator to get an idea of the deck price per square foot. Don’t forget other material costs, such as railing and fasteners. You’ll also have costs related to utilities, drainage considerations and amenities and labor. The larger and more complex the deck, the more time required to install. It is essential to find a contractor with the experience to ensure the integrity of your new deck. 

Additional Amenities

Don’t forget the amenities that will elevate your rooftop deck experience! Here are just a few ways to make the most of your space:

  • An outdoor kitchen provides all the essentials for cooking and grilling without having to go back indoors. Don’t forget to plan for tables and chairs to accommodate all the friends who will want to hang out in your new space.
  • Include an outdoor television or entertainment system to watch movies or dance the night away. Make sure you have cozy furnishings and accents to make your guests feel welcome.
  • Depending on your budget, engineering and the approval of the local building authorities, you might add a fire table to warm up your space.   
  • Build in outdoor lighting to beatify your open-air space and make it safer for guests.

Make Your Rooftop Deck a Reality

A rooftop deck requires an investment, but one that will extend your outdoor living space in beautiful new ways. While planning and some specific materials and experience are required, the deck of your dreams is possible. The first step: find a dealer near you to get the Trex products you need. Happy building!

(NOT ALL PRODUCTS ARE AVAILABLE IN EVERY COUNTRY.)