How to Build a Roof Deck on a Pitched Roof

A pitched roof is the most common type of roof in America. It has a slope that starts steep and gradually becomes less steep as it reaches the other end. Building a deck on top of this type of roof will require some planning, but with these tips, you’ll be able to create your dream rooftop oasis! First, find out if there are any regulations about adding structures to your house.

How to Build a Roof Deck on a Pitched Roof

HOA’s may have rules against building anything that adds height to your home or changes its appearance drastically. Once you’re sure that it’s allowed, talk to an architect or contractor about drawing up plans for what you want so they can calculate how much material will be needed and provide an estimated cost for materials and labor. In this article, we’ll explore how to build a roof deck on a pitched roof.

What You Need

  1. A building
  2. A new roof deck
  3. Scaffolding
  4. Drywall screws
  5. A hammer
  6. A drill
  7. An extension cord
  8. Measuring tape

Step by Step Guide on How to Build a Roof Deck on a Pitched Roof

Step One: Installing the Pergola Posts

The first step is how to build a roof deck on a pitched roof. You will want to get down on your stomach, crawl under the deck and install all posts. You’ll need to use concrete for this step. Ensure to follow your local codes regarding how deep you are required to set the post in concrete, but typically it’s somewhere between 4-6’—drill 4″ holes for the post anchors.

Insert post anchors, set posts in concrete, and secure with the appropriate sized bolts. You may also add 2×4 to the top of each post underneath the deck joist if you choose to. You will need a total of 12 posts to support the weight of the roof and deck.

Step Two: Installing Joists

Once all of your posts are installed, it’s time to build your frame! You’ll want to install your joists first. Depending on the size of your deck, you may need additional lumber for this step. Use a chalk line to mark all of your 2×6’s before cutting them down to size. It’s easier to measure one end and cut it at an angle first, then measure the other side and cut it at an angle.

Once All of Your Posts Are Installed, It's Time to Build Your Frame!

It would be best if you ended up with a 2×6 that is 12″ tall and 5-6′ long. Once all of your joists are cut, use two 4″ lag bolts on each post and install the joists. Leave about 1/4″ to 1/2″ between each joist. You can either choose to use 2×4’s or 2×6’s for this step, depending on the strength that you desire. Here, we use 2×6’s for added support.

Step Three: Installing the Roof Boards

This is the trickiest part of installing a roof deck. We have done this countless times before, but it still can be tricky to get just right! You’ll want to first establish your 2×8’s for the roof boards. Once installed, you will need to build a box using 2×4’s that are the same length and width as your joists. 

His box should be built on top of the joist and sit flush with the outside edge. Once you have made the frame, use a table saw to rip enough shingles to lay over your frame by about 6″. This will give you plenty of room for error when installing them. After cutting them down, apply roofing cement all around the frame and lay the shingles down.

Step Four: Installing Roof Tiles/Shingles

Here you’ll want to install your roof tiles or shingles, depending on what your preference is. You can either use asphalt shingles or clay tile. You can also choose to use metal if that’s the look you’re going for. For shingles, either staples them to the plywood sheathing or tile underlayment according to the manufacturer’s product information.

If your tiles are glued down (which is highly recommended), you’ll need to use construction adhesive and roofing nails sparingly around the perimeter of each piece of roofing material to hold them down. Once your tiles are installed, cover the entire roof deck with a protective layer of underlayment membrane. This will protect the plywood from water damage and rot.

Step Five: Installing Drainage and Extending Downspouts

It’s best to install a layer of waterproofing over the top of your plywood. This will help divert water away from your house foundation and onto your roof deck. It would be best if you also extended downspouts, which you can easily do with copper piping.

Install Extended Downspouts, Which You Can Easily Do With Copper Piping

To create the drainage slope, you’ll need to angle the piping away from your roof deck in a downward direction by at least one inch for every foot of run usually 2-3 inches per foot is sufficient, but this depends on how harsh your climate is). If you’re using plastic downspouts, you’ll want to run it down a 2×4 resting on the ground with a support post under it to ensure that it remains stable.

Step Six:  Building the Frame

At this point, you can now start building your roof deck frame. Use 4×4 posts around the perimeter of your roof deck and 2x4s as the supports and inside flooring beams. Please make sure all of your beams are level with each other before attaching them to the posts. You can use joist hangers or galvanized nails to attach the beams.

Once everything is secure and stable, you can now start laying your decking boards. You want to use 5/4×6 pressure-treated wood for the flooring with a thickness of 3.5 inches. Make sure to stagger the joints, so they don’t line up directly on top of each other and attach using 2 1/2 inch galvanized nails. Use a circular saw to cut the boards if necessary.

Step Seven: Installing Railings and Staining

When installing them, make sure there is a two-inch gap between posts; otherwise, people will fall through them. Next, you can buy railing material or use 2x4s with some plywood for flooring on top of it. Finally, just cut strips about an inch wide and nail them on for stability. You can also stain the boards to give them a more finished look if you want.

The last step is an optional one, but it’s recommended for safety purposes. You can build a simple frame around your roof deck with 2x4s on the outside of it plated with plywood both underneath and on top of it to make it taller, and attach it to the posts and beams to give people more stability and confidence when walking around. Now that you have read this article, you know how to build a roof deck on a pitched roof! Enjoy your new appliance.

Does Adding a Roof Deck Add Value to Your Home?

Roof decks are a great addition to your home. They help you enjoy the outdoors and increase your living space at the same time. Roof decks allow homeowners new opportunities for entertainment and relaxation. A roof deck also allows sun and rain to enter a home quickly. It’s not hard to see how building a roof deck could add value to your home.

The roof deck adds value by increasing the overall square footage of a home. Roof decks can be used for entertaining or relaxation, but they also offer homeowners flexible space not available in most homes. As more people search for homes with additional storage and entertainment space, having a roof deck could help you sell your house faster and for more money than similar houses in your area.

Can I Put a Deck on My Flat Roof?

There are several reasons for wanting to build a roof deck on your flat roof. Some homeowners want to create an outdoor space that is more usable than the typical flat patio; some are drawn to the modern style of a rooftop deck or terrace, while others are taken by the idea of looking down over their neighborhood from high above.

If your flat roof happens to be the only elevated outdoor space in your garden, you might want to consider building a deck that can serve as an alternative or additional entertainment and living area. Roof decks work well for small and large homes alike: they add square footage without taking up valuable square footage on the ground, and when designed creatively, can become a unique retreat.


The benefits of building a roof deck on your pitched roof are plentiful. First, of course, there’s the obvious benefit of adding square footage to your home, but other factors should be considered when deciding whether or not to build a roof deck on this type of structure.

For instance, you will need an engineer to hang anything from the ceiling below the new space. It would be wise to contact someone experienced in working with metal framing for projects like these before beginning construction. We hope you enjoyed this article on how to build a roof deck on a pitched roof.

Check it also – How to Build a Roof Deck on a Pitched Roof .

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