How to Build a Roof Over a Deck

Adding a roof to your deck gives you more living space and is the ideal spot for family gatherings and barbecues.

How to Build a Roof Over a Deck

Building a roof over your deck not only adds value to your home, it also increases the size of your outdoor living space, letting you enjoy your deck for three seasons to four seasons, depending on where you are located geographically. When the sun is beating down relentlessly, or the rain drives you in from the yard, a roofed deck allows you to enjoy an outdoor lifestyle away from the elements.

Getting the Right Support

As with any construction, structural safety is your top priority when thinking about building a roof over your deck. You’ll need to be certain your existing deck will be able to support the weight of your new roof and the weight of everyone who’s going to be spending time there.

Your average deck is built to withstand around 55 pounds per square foot, so if you want to build a porch-style roof, for example, which requires 85 pounds per square foot, you will need to reinforce your foundation, usually by installing more footings beneath your deck. These concrete pillars are often concealed underground so you’ll need to contact a local engineer or contractor if you’re concerned about your deck’s ability to support your roof.

If you plan to place your roof’s supporting posts directly on the deck structure, it’s critical they sit over a support post, not within the span of a beam. If you’re not sure, confirm with an engineer or licensed contractor.

Before you rush off to the lumber yard, check in with your local authority. Some require homeowners have their plans checked by an architect or engineer to ensure any changes you make to the existing structure are within regulations, especially if your area is susceptible to snow or high winds.

Design and Concept

At the design stage, assess the impact the roof will have on other parts of the house. Will it affect the view from your bedroom window? Or will the roof prevent that all-important afternoon light from reaching your living room or kitchen? Your deck will be an important part of your home and should complement the overall look and lines of your house. It's critical to match the pitch angle and overhang of your deck roof to your house. Getting the angle right makes sense aesthetically, but more importantly, you want to avoid leaks. While a flat roof is a simpler build than a pitched roof, it is more susceptible to leaks.

Which Roof is Right for Your Deck?

While you probably have a few ideas of your own, your deck roof’s design will be partly dictated by your deck’s size and shape. Roof types generally fall into three categories: shed, gable or hip roofs.

  • A shed roof has a single, sloping surface that extends from the house wall to support posts. This type of roof works best for long and narrow decks. Deep decks require too much slope.
  • A gable roof is the most common of the three, due to its shape blending in well with most homes. A gable roof forms a triangle, with its ridge running along the deck’s center, and its edges overhanging the deck space.
  • A hip roof has a solid shape which looks appealing, but with four sloping surfaces it requires more support and is complicated to build.

Anchoring Your Roof

Your deck roof will anchor to the outside wall of your house or to the roof of your house. To attach it to the wall, the simplest way is to install a ledger board. This is a sturdy board that acts as a support for any attachments to the existing wall. Then, you will flash aluminum or steel that’s used over construction joints to keep them dry. Attaching your deck roof to your existing roof requires removing the shingles and sheathing to expose your existing roof’s frame. You can then attach the roof rafters to your existing roof rafters.

While building a roof over your deck can be a painstaking and exacting project, the rewards are great. A covered outdoor area means extra outdoor space and the ideal place to throw a family barbecue, whatever the weather.