Can Your Deck Support a Roof?


There are several benefits to adding a roof over your deck. A deck roof will shield you from the rain and the blazing sun. Increasing your comfort with the added shade during the heat of the day. It must be our shared fear with chicken little, but a roof over our head increases our sense of feeling safe and comfortable. A roof over a deck can improve the look of the deck and house.

But can your deck support a roof?

A deck needs to be designed for a roof and can not be added later on without a few considerations. A deck roof is heavy, and in a colder climate must be designed for additional snow load. A deck supporting a roof must include appropriate footing and beam size along with structural point load support.

An uncovered deck built to code is not strong enough to support a roof. The additional weight of the roof cannot be support by the existing structure. A roof over a deck needs to be part of the original design and construction or treated as a renovation. When additional footing support can be added along with reinforcing the deck’s beams as required to support the extra load.

A covered deck is not the same as an open deck regarding construction. In Calgary, where I build decks, the city rightfully considers a deck a single-story building. Which it is, with all the structural elements of a house at play. You have a roof, the point of our conversation, being supported by trusses, and posts bearing on a foundation. All the elements of constructing a house. No small undertaking, which must be considered when adding or building a roof over a deck.

Add a deck roof incorrectly will not only cost you money when it collapses but also puts people at risk of injury or death. A roof following down on you is not something to be taken lightly. Like seriously, a roof is heavy. Even a deck roof!

Things so consider when adding a roof over a deck

A roof over a deck should be part of the original design and construction, but still, we must consider these elements when building the deck. The soil bearing capacity. Required footing size, along with the location of the post in relations to the deck footing and beams. Some of these things can be calculated and designed with your local building code, but often a covered deck will involve an engineer to verify load and support. Consult your regional permitting offices before proceeding, but here are some areas that will need to be analyzed.

Deck footing size to support a roof

The size of the footings required to support an uncovered deck is smaller than to support a deck and roof. Not direct correlation, but in Calgary, an uncovered deck pier footing requirement is 10” (250mm) diameter concrete column. A single-story house strip foundation requirement is 24” (600mm). Almost two and a half times the size. Adding on top of that is most deck roofs are point loaded. Meaning that you will have a limited amount of post bearing on individual footings. Requiring a more substantial footing to achieve enough soil bearing to support the weight of the roof.

Deck beams size to support a roof

Deck’s beam and joist are designed to 0.5 kPa (10 psf) Dead load and 1.9 kPa (40 psf) live load. This is true both in Canada and the United States. To see the 2015 International Residential Code click hereOpens in a new tab.. In short, your deck’s current beams and joists are only designed to support a limited deck weight, but the addition of a roof will require additional support. This may mean adding an additional ply to the beam or reducing the span between footings. Whatever the solution is. It needs to be accounted for during the construction of the deck before adding a roof.

Bearing location of the roof over a deck

For a concrete pad, you may be able to attach post brackets anywhere on the pad to support a small roof but not so with a deck. Installing a post on decking between joists will cause the weight of the roof to punch the post right through the decking. Causing the roof and deck to collapse. I don’t know how many thousands of “squash blocks” I have installed in my career, but I assure you that whenever you have a focussed load, you need support directly under it. Either in the manner of additional beams or blocks to transfer the load. Decking alone cannot support the weight of a roof.

Speaking of Supporting a Deck Roof

There are many options to support a deck roof, but I think 6×6 cedar post is the best. Cedar posts naturally are most resistant to rot. Also, cedar, if you choose not to regularly stain, will beautifully grey but still maintain a majestic look about it.

Using larger 6×6 cedar post even if the larger size is not required adds dimension to the deck support. Bringing the feel of large rustic wood posts from another era to your deck.

If you choose not to have a wood pergola with its upkeep composite is another option. Structurally a composite pergola often is supported with metal posts inside a composite sleeve or several other structural elements.

How ever you choose to support your deck roof, make sure that it is structurally sound and meets local building code. Which leads us to our next section, permits for deck roofs.

Required permits for a deck roof

Not only does your deck construction need to be able to support a roof, but there are also legal requirements in adding a roof to a deck. Depending on the size of the deck roof and construction. Every jurisdiction will vary in required permits and restrictions, but I am going to use Calgary, Alberta, where I build decks as an example. Hopefully, helping in thinking about permits and restrictions in building a roof over your deck.

Size matter with Deck Roofs Permits

The size of your deck roof will impact which permits will need to be applied for.

“It is greater than 10 m2 (107 sq. ft.).”

CiOpens in a new tab.ty of Calgary

Anything decks roof larger than 10 m2 (107 sq. ft.) will require a permit in Calgary. The same limit is in place in Toronto for deck roofs. So, if you keep it small, no need to apply for a permit, the same with decks. If a deck is less than 24” (0.6m) from the ground, no permit is required.

If the deck roof is not attached to the house, it becomes an outbuilding still requiring a permit but limited in scope and requirements. One caviar, the roof must be 1.0 m (3.2 ft.) from the house. That puts a little damper on a deck roof put still is a simple permit process if designed correctly.


Attaching a deck roof changes the required permits

The most straightforward deck roof construction beside your house is to attach it to the house. But this is a no, no regarding deck roofs. Attaching a deck roof to the house changes the required permit into an addition. A house addition is a much larger permit application and fee. The construction permit must include a development permit as you have now changed the look of the neighbourhood.

“It is attached to a house.”

City of CalgaryOpens in a new tab.

This additional permit is partly to blame because of the ease of transforming a covered deck into a sunroom. Or I have even seen covered decks be enclosed with walls and becoming an extra room on the house. Which is what the city is trying to prevent, unpermitted decks becoming poorly constructed house additions. Decks with roofs need additional structural construction but still do not meet the requirements for a house addition. In the past to many have been given an inch and taken a foot. Now we all have to pay the price.

Now that you know some of what is required for a deck roof. If it is feeling like too much. Here are some deck shade alternatives.

Deck roof alternative

Maybe a permanent, heavy deck roof is not the right answer for your deck. Something not requiring large structural support, or less permanent thus not requiring a permit. Here are a few ideas to ponder to shade your deck.

  • Retractable awning
  • Patio umbrella
  • Sun sail
  • Privacy screen casting shade over your deck

If it is just that your deck is too hot, there are some other ways to cool your deck. Click hereOpens in a new tab. to read the full article.

Whatever you do, add a roof for your deck or less demanding shade elements. I hope your deck brings you joy as your outdoor living space.

Ryan Nickel

A Red Seal carpenter, passionate about building decks to be enjoyed.

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