How to Build a Roof For Your Home, From Start to Finish

Roofs are the finishing touch on every home that literally gives your household shelter from a storm. If you're an avid DIYer with a wealth of contracting experience, you may consider building your own roof without the help of a contractor. But building a roof requires framing skills and attaching layers of roof material, all at a height far above the ground. If you have the skills and experience to build your own roof, our DIY guide can teach you just how to do it.

Planning to Build a Roof

Before jumping into your roofing project, take some time to plan each step to avoid any missteps. You will need to choose your roof style, materials, and more.

Choose a Roof Style

There are several types of roof designs, from gable to hip to gambrel and more. In this guide, we will be building a gable roof, as it is the most popular type. A gable roof has two evenly sloping sides and can be built with most roofing materials.

Select Materials

You will need to make purchasing decisions on several materials for your new roof. Materials include lumber, underlayment, sheathing, fasteners, roof covering, and more. Compare these materials' cost, quality, and durability and make an informed decision. After all, the typical lifespan of a roof is 30 years, or longer with proper maintenance, so it's worth investing in high-quality materials. 

When purchasing lumber for the roof framing, you will need to consider the size and spacing of your rafters as well as the strength of the lumber. Roof rafters must be made from a single piece of lumber. Once you know the required length of the rafter boards (see below), purchase lumber that is at least a foot longer, plus the length of your overhang.

Consider Drainage

The rain that falls off of your roof has to go somewhere. Proper drainage should be considered when choosing your roof style and pitch, and how you will manage the rainwater. Rain gutters carry water away from your roof, and are a vital part of your roofing system. It’s crucial to install gutters after building your roof.

Consult an Expert

A lot goes into designing a roof, and unless you are an architect or an engineer, you likely can't do it alone. Consult an expert to help plan out the ideal dimensions of your roof structure and the pitch, rafter spacing, etc. You will also need to speak with your local building code office to get a building permit and follow the proper approval procedures.

Gather Assistants

Building a roof is not a solo endeavor. You will need at least one other person, ideally, two, to help lift boards into place and secure roofing layers. Also, plan on spending more than just one day on this massive project, it will likely take a few.

Roof Framing: Trusses vs. Rafters

When building a roof, you can choose to use either pre-built trusses or custom-built rafters. Pre-built trusses are manufactured at a separate facility to fit the dimensions of your home. They are shipped to the site, then lifted into place, usually with a crane, but many hands and adequate rigging will also work. Pre-built trusses are convenient and a time-saving option.

Custom-built rafters are built as part of the roof framing process at your residence. Individual framing members are cut and assembled together. Rafter framing is usually best for smaller projects or unique roof lines, and is the type of framing used in this guide.

How to Build a Roof in 9 Steps

Building a roof can be broken into four phases: framing, sheathing, underlayment, and covering. Framing is the most complicated and strenuous part of the project. Be sure you thoroughly know the parts of a roof before continuing.

1. Check Wall and Ceiling Framing

Ceiling and wall framing should already be complete on the building you will be adding a roof to. Your structure should have exposed ceiling joists that run the entire span of the walls and rest on top of the wall framing.

Ensure the existing framing and joists are plumb and level. If not, you risk building a roof that is also not level and may not function properly.

2. Determine Roof Measurements and Pitch

Before cutting any boards for your roof, you need to take a few measurements. These measurements have specific names as follows.

• Span: The horizontal distance between the wall framing.

• Rise: The vertical distance from the ceiling joist to the ridge board.

• Run: Half of the span distance.

• Line: The diagonal distance from the wall framing to the ridge board.

To determine the “rise” and “line” measurements and the placement of the ridge board, you will need to know your roof pitch. Roof pitch is “rise” divided by “run.” In other words, if a roof rises vertically 6 inches in every run horizontally of 12 inches, the pitch would be 6:12. 

Review your local building codes and speak with a building official to find out the requirements for roof pitch in your area. If you are using asphalt shingles as your roof covering, a minimum slope of 2:12 is usually required.

3. Mark and Cut Roof Rafters

Once your roof measurements are figured out, you can begin to cut boards for the rafters. Use a pencil and framing square to mark the cut lines. When using the framing square, it must be angled to match the pitch of your roof.

• Plumb Cut: Located at the top of the rafter where it meets the ridge board. With the framing square long arm on top of the rafter board so that the short arm sits upright, draw a line along the outside edge of the long arm.

• Bird’s Mouth: Located where the rafter meets the top of the wall plate. It is made up of two cuts called the heel cut and seat cut.

  • To mark the heel cut, start at the plumb cut line and measure until you reach “line” distance. At this point, place the framing square in the same position as before and mark a line parallel to the plumb cut.

  • To mark the seat cut, turn over the framing square and hold it perpendicular to the heel cut line. Match the long arm measurement at the bottom of the rafter with the width of the wall plate and draw the line towards the heel cut marking.

• Tail Cut: Located at the opposite end of the rafter that creates the roof eaves. The location of this cut depends on your roof’s soffit and fascia.

Repeat these markings across all of your rafter boards and complete the cuts with a circular saw.

4. Install Ridge Board

Since the ridge board is ultimately supported by the rafters, you will need to temporarily support the ridge board to get it into place initially. Nail a board in the center of each gable wall end of the roof and temporarily place your ridge board on top.

5. Install Rafters

You will need multiple helpers for this task. It is now time to install the cut rafter boards. Start by hoisting two rafters up to the roof surface and plan to install one on each side of the ridge board on a gable wall end.

Fasten one end of the rafter to the wall plate. Repeat this step on the other side of the roof with the opposing rafter board. Lean the two rafter boards into each other so they stay vertical, but have one of your helpers hold the boards in place.

Repeat this process with two rafters at the other gable wall end. Once the four rafters on each end are secured into the wall plate, lift up the ride board and fasten it in between the rafters.

With the ridge board in place, you can now begin to install all of your rafter boards and complete the roof framing. If any additional framing is required by code, such as collar ties, purlins, or sway braces, now is the time to install those.

6. Place Roof Sheathing

Once the roof framing is complete, you can begin to install the layers that make up the roof surface, starting with the sheathing. You will place the sheets of sheathing in rows, starting with the bottom of the roof and working your way up towards the peak. Fasten the sheathing to the roof framing with common nails and stagger the pieces so you do not have long lines of joints.

7. Install Drip Edge

A drip edge is a metal flashing that protects the sheathing from water. Secure the metal flashing along the entire edge of the roof, slightly overlapping each section as needed.

8. Roll Out Underlayment

Underlayment is the next roofing layer—it serves as waterproofing to protect the sheathing and framing beneath should water penetrate the roof covering. Underlayment is usually a felt material that comes in rolls. 

Roll out the underlayment from the bottom of the roof to the roof peak, overlapping each section as you go. Once you have underlayment installed on both sides of the roof, roll a final layer over the ridge.

9. Install Covering

Last but not least, install your roof covering of choice. Most homeowners choose asphalt shingles, but you could also pick metal roofing, wood shingles, etc. Whatever type of roofing you choose, you will install it from the bottom up to the peak with slight overlapping. Follow the manufacturer’s recommended installation instructions from the product you purchase.

DIY Building a Roof vs. Hiring a Pro

Learning how to roof a house and then embarking on the project is a feat very few homeowners are willing to take on. You need some type of past building or carpentry experience to know how to make the proper cuts, sling and install boards, and maintain a roof pitch. According to HomeAdvisor, labor fees make up about 60% of the cost of installing a new roof. So while you’d save substantially on the cost of labor if you build a DIY roof, hiring a local roofer is the best way to go—for a few reasons.

First and foremost, a trained roofer will help with the initial design of your roof. You can feel confident knowing your roof will be the right pitch, drain water properly, and keep water out of your home. The professional roofing company will also suggest the best materials and likely finish the job a lot faster than you would have. When it comes to large-scale and impactful projects like building a roof, leave it to the experts.