How to Shingle a Steep Roof Safely, from 8/12 to Mansard Pitches
On a steep roof nothing stays where you put it. Jacks, planks, anchors and extra fasteners are part of the method, not extras.
- Professional
- 2 to 5 days
- Updated
The short answer
On roofs of 8/12 and steeper, work from roof jacks and planks, stay tied off to properly installed anchors, and keep materials blocked or hoisted in small amounts. Fasten with 4 nails as standard and 6 nails plus hand-applied roof cement on very steep slopes, commonly at or above 21/12, per the manufacturer. Move and cut shingles with extra care, and use a lifeline on every steep slope.
A roof of 8/12 (about 34 degrees) is steep enough that you cannot stand on it and work for long without support. At 12/12 it is 45 degrees, and a mansard or a tower roof can go beyond 60 degrees. On these roofs, everything that is easy on a low slope is harder: walking, carrying, holding a bundle, cutting, even keeping your nailer from sliding. Falls on steep roofs account for a great share of roofing injuries, and the method is built around preventing them.
The second problem is the shingle. Steeper roofs shed water faster, but they also put more load on each nail and each sealant strip. Manufacturers call for extra nails and hand sealing above certain pitches, often around 21/12 (60 degrees), and some ask for them at lower pitches in high-wind areas.
This guide covers staging, materials and fastening on steep roofs. The general field method is in how to lay shingle courses and offsets. Fall protection is covered in how to install a roof anchor and how to set up a lifeline and rope grab.
Tools
- Roof jacks and staging planks
- Roofing coil nailer and compressor
- Hook blade utility knife
- Fall arrest harness, lifeline, rope grab and anchors
- Chalk line
- Ladder hoist
- Caulking gun for roof cement
Materials
- Laminated asphalt shingles
- Roofing nails, 1-1/4 inch galvanized, or longer where required
- Asphalt roof cement for hand sealing
- Underlayment with cleats or traction
- Toe boards or cleats for staging
- Planks for jacks, sound and straight
Safety first
- Fall protection is not optional. WorkSafeBC requires it where a fall could be 3 metres (about 10 feet) or more, and on steep roofs a slide can be fatal from any height. Use a harness tied to an anchor above you, with a rope grab.
- Never walk a steep roof without jacks or a secured platform. Wet underlayment, granules, frost and moss are slippery at any pitch.
- Keep tools on lanyards and materials blocked. A dropped knife or a sliding bundle reaches the ground fast.
Step by Step
Step 1: Plan the fall protection before anything else
Anchor points go near the ridge, into framing, and follow the anchor manufacturer's installation. A lifeline with a rope grab lets each worker move up and down and across without unclipping. See how to fit a fall arrest harness and how to set up a lifeline and rope grab.
Set up a ladder that extends well above the eave and is tied off, and keep the area below clear. Check the WorkSafeBC OHS Regulation Part 11 and get training before using fall arrest equipment.
Step 2: Install underlayment with traction in mind
Many synthetic underlayments are designed with a slip-resistant top. Wet felt and smooth synthetics are slippery on a steep roof, so keep the work to a dry window and lay only what you can cover before the end of the shift. See how to install synthetic underlayment.
On steep slopes, use more fasteners than the minimum in the underlayment instructions, and cover it before the next weather.
Step 3: Set the roof jacks and planks
Jacks are nailed through the shingles and into the rafter, at the spacing the jack manufacturer specifies, commonly 4 to 8 feet, and each plank must rest on at least two jacks. Use planks that are straight and free of knots, such as 2 by 10 or 2 by 6 lumber, with a toe board where needed. See how to install roof jacks.
Work from the plank and move the jacks up as courses are finished. Each jack is removed later, and the nail holes are sealed with roof cement.
Watch out: Do not rely on a plank or jack as fall protection. They support the work. The harness and lifeline protect the worker.
Step 4: Stage materials in small, blocked amounts
A bundle left on a steep slope will slide. Put bundles on the plank, in a pocket, or held by cleats. Use a ladder hoist to bring up small loads. See how to load and stage shingle bundles.
Keep offcuts and debris off the roof surface, where they become footing hazards. Use a bucket or a tool bag.
Step 5: Lay the courses with extra fasteners
Four nails per shingle is standard up to a steep pitch, and 6 nails are commonly required at or above about 21/12. Some manufacturers also require 6 nails from a lower pitch such as 12/12 in high-wind regions. See shingle nailing: placement, count and depth.
Work along the plank, kneeling or sitting on it when the slope allows. Snap lines on the dry underlayment, and keep courses straight as for any roof. See how to snap chalk lines for shingle courses.
Step 6: Hand seal the shingles where required
The factory sealant strip may not be enough on a very steep slope, where gravity pulls the tab and the sealant bond is under constant load. Manufacturers often require hand sealing with dabs of cement about the size of a quarter, placed under the tab at set points, at pitches of 21/12 or steeper.
Do not use more cement than called for. A large blob can cause blisters and staining. Press the tab gently into the dab.
Step 7: Cut and handle shingles on the plank
Lay the shingle flat on the plank or a bundle, cut from the back with a hook blade, and keep the blade moving away from you. See how to cut asphalt shingles cleanly. Never cut on your knee on a steep roof, where a slip is not recoverable.
Drop nothing from the roof. A tool or a bundle falling from a steep roof can kill someone below.
Step 8: Remove the jacks and finish the ridge
Pull each jack up and out, then slide a shingle over the hole or fill it with cement and a patch of shingle. The jacks go last, working down from the ridge.
Cap the ridge from a platform or with the harness tied to the ridge anchor. See how to install hip and ridge cap shingles.
Mansard and Very Steep Sections
Mansard roofs have a lower slope that can be 60 degrees or more, sometimes close to a wall. Shingles are permitted on many mansard slopes, but manufacturers apply their steepest requirements: 6 nails, hand sealing, and often a product rated for it. Some will not warrant shingles beyond a stated pitch. The alternatives are metal, slate or cedar. See metal roofing and install synthetic slate and shake.
Pitch Reference
These are the approximate angles for common steep pitches.
- 8/12: about 34 degrees.
- 10/12: about 40 degrees.
- 12/12: 45 degrees.
- 18/12: about 56 degrees.
- 21/12: about 60 degrees, where manufacturers commonly call for 6 nails and hand sealing.
Common Mistakes
- Relying on friction or boot traction. Wet underlayment and granules are slick, and steep roofs do not forgive a slip.
- Working without a lifeline. A harness tied to a short lanyard at the wrong anchor can be worse than none.
- Piling bundles on the slope. They slide, and a sliding bundle is a hazard below.
- Using 4 nails where 6 are required. The roof passes inspection and fails in a storm.
- Skipping hand sealing. Tabs droop and lift on steep slopes.
- Leaving jacks in. Nail holes through the shingles leak.
When to Call a Professional
Steep roofs are a professional job. The fall protection set-up, the staging and the fastening all call for training and equipment that most homeowners do not have, and a fall from a steep roof is often fatal or life-changing. Hire a roofer.
Ask any roofer you hire about their fall protection plan and their WorkSafeBC coverage. A quote that does not include the staging for a steep roof has left something out.
Fraser Roofing does free roof inspections across the Fraser Valley, from Hope to Abbotsford. See our Roof Replacement service or the towns we cover.
How to Shingle a Steep Roof: Questions
What pitch is considered a steep roof?
Roofers usually call 8/12 and above steep, which is about 34 degrees. At that angle, staging such as roof jacks and planks is commonly needed to work safely. Pitches of 12/12 (45 degrees) and above are very steep, and manufacturers often change the nailing and sealing requirements at about 21/12 (60 degrees).
How many nails do you need on a steep roof?
The standard is 4 nails per shingle, but many manufacturers require 6 nails on steep slopes, commonly at or above 21/12, and sometimes at lower pitches in high-wind areas. The wrapper and installation instructions give the requirement for each product, and it is also tied to the wind warranty.
Do steep roofs need hand sealing?
On very steep pitches, commonly 21/12 and above, many manufacturers require dabs of asphalt roof cement under each tab in addition to the factory sealant, because the sealant strip alone may not hold against gravity. Read the installation instructions, since the pattern and pitch vary by product.
What are roof jacks used for?
Roof jacks are steel brackets nailed through the shingles into the rafters that hold a plank, creating a level platform on a steep slope. They give a place to stand, kneel and set bundles. They are staging, not fall protection, so the worker still needs a harness and lifeline.
Can you shingle a 12/12 roof yourself?
It is not recommended without training and proper equipment. A 12/12 roof is 45 degrees, steep enough that you can slide from any point. Falls from steep roofs cause serious injuries even at low heights. A roofer with staging, anchors and experience does this work far more safely.
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This guide is general education. Always follow the product manufacturer's installation instructions, the BC Building Code and WorkSafeBC requirements, which take priority over anything written here.
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