How To Build A Roof Over My Existing Deck

How To Build A Roof Over My Existing Deck

Always try to match the house roof pitch angle and overhang for your shed roof. Some shed roofs are designed to be nearly flat. Flat roofs are more susceptible to leaking than pitched roofs. Shed roofs project as a single plane roof pitched away from the house. If you are tying the roof directly to a house wall, you can install a ledger board with flashing and install rafter ties to attach the rafters at the appropriate angles or use engineered trusses. The opposite side of the porch roof will be supported by a header beam that is installed parallel to the house on top of 6×6 support posts. Support posts should be spaced less than 8′ apart and be located on top of properly sized frost footings. Rafters should be attached to the header beam using hurricane ties.

If you are tying the shed roof into an existing roof on the house, you will need to remove the shingles and sheathing to expose the roof framing. You will need to attach the porch rafters to the house roof rafters and replace the roofing and flashing. Looking for home deck services? Look no further! Hitch Property Constructions has you covered.

Many building departments require a local architect or engineer to design plans for porch roofs because of the increased snow, roof and wind loads created by adding a roof.

Adding a Roof Over an Existing Deck

Often when we build a deck on the house, it only takes a little time in the heat of the summer sun, and we quickly realize it would be nice to have some shade when enjoying the outdoors. How hard is it to install that roof over your deck to achieve that oft-needed shade? It really depends. If you have a single-story dwelling, then adding a roof may mean you have to build a gable (A-frame) roof and then tie that into your existing roof. That can be a little complex for your Do-It-Yourself project. If you have a 2-story home and you are simply adding the roof to the side of your home, as in our recent project shown here, then this may fall under the category of “doable” for you depending on your carpentry skills. This week I will walk through the steps of building that easier of the two-deck roof pointing out tips that will help to make it as easy as possible.

  • Check with your local building department and apply for any permits you will need. Typically, you will need a building permit and at least a readable sketch of what your addition will look like. You will have to fill out a few forms detailing what size lumber you intend to use and centre spacing. Most building departments will help you with answering those questions as you apply for the permits. Once you have the permits and have worked up a material list, go ahead and get your material. Hitch Property Constructions has a wide range of decking services Melbourne services.
  • Setting your ledger board. The ledger board is the point at which you will attach your rafters. It will attach directly to the side of your house. You will need to clear space for it by removing the siding. Note where the studs are and mark their locations. You will use those studs as anchor points to secure your ledger board. The ledger board needs to be secured properly in order to support the rafters that will be attached to it. You can’t depend on nails to hold it securely so use either 4″ lag screws or I like to use Ledger Locks. This is a newer product that is engineered just for this purpose. Most municipal building departments will accept them instead of lag screws or carriage bolt, and for me, they are well worth the little extra expense in the time they save on the job. If you put 2 Ledger Loks per wall stud and you can rest easy at night knowing that that ledger will hold any snow load put on it here in central Virginia.
  • Building the support beam. There are two areas that need extra attention because of the weight they will have to support in building your roof. The ledger board attached to your house that supports one end of your roof rafters is the first. The support beam that supports the other end of your rafters is the other. The size of lumber you will need for your beam will depend on the distance it is from the ledger wall. The greater the distance of the span, the bigger the rafter size will need to be and the heavier the beam will need to be. In the job pictured, I was spanning 12 feet and so used 2×8 rafters. The support beam out front was constructed of 3- 2×10’s. The overall length of the beam was 20 feet. A beam that big when completed is pretty heavy and needs good supports. In this case, we used four 8″ fibreglass composite columns. Each column is rated at 10 tons which may seem like overkill, but considering the weight of the roof and the potential for the occasional heavy wet snow, it really is about right. Optimally, one would like to build this beam on the ground and then lift by machine into position. You can build it in place a piece at a time (like I did) even by yourself (like I did) if circumstances warrant. I built temporary supports (3 of them) and then installed the sideboards going from the house to be attached to the beam, and then built the beam one or two boards at a time (depending on the weight and how early in the day it was). As I put up each board of the nine, I would end up using. I would attach it to the end board or the previously installed board. When it was all in place, I then used 4 ½” Header Loks to pulled it all together tightly. (Tip: once it is up and tied together, it won’t necessarily be straight. You will need to stretch a string down its length and then use boards to push and pull it into a straight line. This will help with the next step.)
  • Setting the rafters. To get the rafters to set flat on your beam and the birdsmouth to fit flush to the outside of the beam, you will need to know your roof pitch. I will take a little extra time working out the exact pitch where the rafter hits my ledger board. Once I have that I will tack it up temporarily and then holding it on the beam end, scribe the exact size and shape of the birdsmouth. Once I have that right I use that board as the pattern and make all succeeding rafters the same. (Tip: It is very important that before you start setting rafters, make sure your beam is square to the house.) The rafter end attached to the wall ledger board will need additional support, so use an engineered rafter hanger. This will also make the building inspector happy, especially if you fill every hole in the strap with a nail. You should also on the beam side tie down your rafters with an approved “hurricane” clip.
  • Attach sub-fascia. (Tip: Use a string to mark all the rafter tails at the desired length.) I usually measure out about 10 ½” so that when complete I have about a 1-foot overhang. Using a stretched string to mark your rafter tails will give you a nice straight line. Then cut them and nail on your sub-fascia. Your ready now for decking.
  • Decking your roof. Most decking is done with 7/16″ OSB. Use galvanized 6 or 8 penny nails and remembered to nail a consistent pattern of at least five nails in the centres and on the edges double that. Remember to stagger your joints so that no adjacent succeeding row of OSB ends up on the same rafter previously used for a joint.
  • Roof felt and Shingles. Before you put felt or another approved barrier down, make sure and install weather guard barrier to the outer 3 feet of the roof (front edge and both sides). This will prevent water seepage back up under shingles from ice and snow build up on a roof. Follow installation instructions on felt and shingles.
  •  Framing in the gable sides. On the sides from the sideboards to the edge of the last rafter, you will need to frame in that area and cover it with 7/16″ OSB. Just put your 2×4’s on edge and space them every 2 feet. Cover with OSB and then an approved house wrap. That house wrap is a moisture barrier that you will need for your “veneer” inspection. It won’t pass inspection without it.
  • Call for your framing and veneer inspections: At this stage, call for your inspections. Building inspectors will look for many of the things already mentioned in the above: Proper lumber size, proper spacing between rafters, rafter hangers, hurricane clips, proper ledger fasteners, and house wrap for the veneer.
  • Finishing touches; Once inspections pass, put on your siding on the gable ends. Put on your fascia board and soffit. The last thing to do it to wrap you beam with trim coil and install a ceiling. I will describe those steps in the next post.
How To Build A Roof Over My Existing Deck 2

Reasons To Build A Roof Over A Deck

As you can imagine, there are plenty of benefits of building a roof over your deck. Here are the top reasons why you’ll want a roof for you

Protection From The Sun And Rain

The most common reason why people build roofs over decks is for protection from the sun and rain. A covering allows you to sit outside and enjoy nature on even the sunniest and rainiest days. During the height of summer, when the sun is at its hottest, catching some shade on your deck is a great chance to relax for you and your loved ones.

Barbeque Throughout The Year

By putting a roof over your deck, barbeque season doesn’t have to end with the last of the fireflies. You’ll be able to enjoy barbequing throughout the year even when it isn’t warm and dry. It might take food a little bit longer to cook in the cooler months, but it’s worth it for some tasty burgers, ribs, or grilled veggies. Check out our Melbourne decking services services here.

Dry Clothes Outside

If you like hanging your clothes outside to dry rather than throwing them in the dryer, a roof over your deck will be the perfect solution for those rainy days. You’ll be able to save money on electricity by drying them outside underneath the roof.

Help Plants Grow

Green thumbs will also love having a covered deck when spring rolls around. You’ll be able to climatize the seedlings and plants to the conditions by placing them in a sheltered location and ensuring they get some sun every day.

How To Build A Shed Roof Over My Existing Deck

Unless you’re experienced in residential roofing construction, you probably don’t want to build the roof yourself. However, you might want to know the process of how it’s done. Take a look at our step-by-step guide for building a shed roof over your existing deck:

  • Before you begin, make sure you’re matching the house roof pitch angle and overhang for your roof.
  • Install post base connectors. These are used to attach the support posts to the frame of the deck. For a solid connection, you’ll have to make sure the frame has the appropriate blocking.
  •  Install the support posts to the post base connectors.
  •  Keep the support posts in place by installing temporary bracing. The tops of the support posts should be notched to hold the header beam.
  • Install the header beams to the support posts. We recommend using thru-bolts for a strong connection.
  • Install the ledger board, which will support the rafters. You can install it by flashing and bolting in place to the house wall.
  • Mark and cut your rafter angle to the roof pitch and then lay out your rafters. Nail the rafters in place to the ledger board.
  • Attach the rafters to the header using framing nails.
  • Create the subroof by installing the roof sheathing over the rafters.
  • If you have any questions about the process of building a roof over a deck, you can contact a local roofer to learn more. In fact, they’ll be happy to answer any questions you may have concerning any part of your home’s exterior, from the roofing and siding to the windows and doors. We’re all about keeping you and your family safe, warm, and dry.

Average Cost To Build A Roof Over A Deck

Decks and patios enhance any home’s living and entertainment space, and adding a roof to that extension can further increase their function and value. However, we’re sure you’d like to know the average cost to build a roof over a deck before you make any decisions.

Unfortunately, we wouldn’t be able to tell you how much it would exactly cost to add a roof to your deck without scheduling a consultation and coming to your home. But we can give you an average range of prices that it would most likely fall within. They include:

Adding any deck covering or enclosure will typically cost between $1,000 – $10,000.

Adding a covered roof to your deck will typically cost between $3,000 – $10,000.

The cost will vary depending on the professionals hired, materials used, square footage, and weather conditions.

Roof Over Deck Designs

Let us know if you like any of the styles from the images in the section above. As for design, there are three main types of roofing that you can choose for your deck. They include:


Gable roofs are easier to build since they don’t require complex roof framing. They have gables at each end and sloping sides.


Hip roofs are similar to gable roofs since they have sloping sides; however, they’re reconnected without using gables. On a deck roof, the supports should have a finished look since they’ll be exposed rather than hidden.


This is the most common option for deck roofing because it’s the only one that works with the architecture for many homes.

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