Hip and Valley Roof Framing: A Comprehensive Guide

Hip and valley roof framing is a fundamental aspect of building design, and understanding its intricacies is crucial for any builder or homeowner. Hip roofs are the most common type, with four sloping sides and a ridge beam at the top, creating a stable and weather-tight structure.

A hip roof's design allows for equal weight distribution, making it more resistant to wind and snow loads. The slope of a hip roof can vary, but a steeper slope is generally preferred for areas with heavy snowfall.

A valley is the area where two sloping sides of a roof meet, and it's a critical point in the framing process. The valley's shape and size will determine the type of flashing and roofing material needed to ensure a watertight seal.

Worth a look: Single Sloped Roof Shed

Calculating roof angles is a crucial step in hip and valley roof framing. You'll need to determine the acute angle where each rafter intersects the hip or valley.

To do this, reference your full-scale drawing on the plywood and use your framing square set to the specific roof pitch. For example, if your common rafter has an 8:12 pitch, align the framing square on your full-scale plan with the 8 rises on the blade and the 12 inches of run defining the angle.

You can also use a construction calculator to find the exact degree of the intersection. Simply enter the pitch to find the precise angle, just like plugging in '8' as the rise and '12' as the run for an 8:12 pitch.

Mark these lines on the plywood, and then transfer this data to the actual rafters. Use a ruler or a straightedge to extend these lines from the full-scale drawing onto the physical materials, creating cut lines that reflect the exact plan angle you've calculated.

A precise backing cut is also essential for making sure the roof sheathing lies flat against the hip or valley rafter. This involves shaving off a slight bevel that matches the slope of the intersecting roof planes.

Here's a quick guide to making a backing cut:

Double-check your cuts by placing the rafter in its intended spot on the roof framing, ensuring the cut edges sit flush against the intersecting rafters.

Marking the roof is a crucial step in hip and valley roof framing. First, you need to establish the plan-view angle of the hips and valleys by determining where the two pitches come together.

The key is to mark the centerline, which is the plane point where the sheathing hits the fascia. To do this, measure 8-7⁄8 in. from the plane point along the 7-in-12 plate line and mark it.

This centerline never moves, and it's the shared center for both hips and valleys. Marking it as the centerline helps keep track of what's what.

Mark the Centerline is a crucial step in roof framing, and it's essential to get it right. This line never moves, and it will always be there to guide you.

To establish the centerline, you need to determine where the two pitches come together. This is where the 7-in-12 and 12-in-12 pitches meet, and you can use a construction calculator to figure out the exact location.

Punch in 15-1/4 in. 'RUN', 7 in. 'PITCH', then hit 'RISE', and you'll get 8-7/8 in. of rise. This is the same for the 12-in-12 side of the hip, as it's a 45° angle from horizontal. So, 8-7/8 in. 'RISE' on a 12-in. 'PITCH' is 8-7/8 in. of run.

To locate the intersection of the 7-in-12 and 12-in-12 on the plate line, measure 8-7/8 in. from the plane point along the 7-in-12 plate line and mark it. Strike a line from the center point on the fascia corner through the mark on the plate line, and extend this line to the edge of the sheet. This becomes the shared center for both hips and valleys.

This line is the key to keeping track of what's what, so make sure to mark it clearly.

Consider reading: Pitched Roof Slope

Mark Bird's Beak, a crucial part of any roof, and yet often a source of confusion. To mark bird's beak, start by drawing a line across the hip from the point where it hits the plate line, labeling it "BM LVL HIP" for clarity.

The hip rafter's run is just the hypotenuse of the triangle formed by the two plate lines. To calculate it, you'll need to know the run to the ridge from both plate lines.

When marking the birdsmouth, it's essential to note the distance from the outside corner to the edge of the hip rafter, which is crucial for marking the plate line when assembling the roof. In this case, it's 8-3⁄8 in.

To determine the hip rafter's length, you'll need to calculate the deductions or additions to the runs for each pitch. For example, if the hip moves away from the 7-in-12 plate line, you'll need to subtract the distance from the corner to the center of the birdsmouth from the run on that side.

Discover more: Do You Need Collar Ties with Ridge Beam

To shift the hip rafter location for uniform overhangs, use the French scribe technique to accurately measure and mark the new location.

Precise measurement is key when moving along the roof's edge to adjust the hip's placement. Typically, you measure the offset required, then mark it on both the drawing and the actual hip rafter.

Recommended read: How to Measure a Hip Roof

The French scribe technique helps in creating a "plumb-line shift", which balances the two sides of the hip rafter. This shift is essential for maintaining symmetry and avoiding unevenness.

Mark equal distances from the fascia's front plane to establish the centerline of the hip rafter. These measurements create a precise plumb-line shift, ensuring uniform sheathing and avoiding structural issues.

To ensure accurate marking, keep the main and secondary centerlines orthogonally aligned, maintaining symmetry over the hip rafter. This minimizes structural issues downstream.

By aligning your birdsmouth cuts against the marked lines, you can ensure they exactly account for the shifted hip rafter positions.

Assembling the roof is a crucial part of building a hip and valley roof framing. The first step is to attach the centering rafters and lift the ridge beam into place. This is done by placing 4-6 common rafters in their designated positions along the longest walls and nailing them firmly to the wall with a nail gun.

Suggestion: Shed Roof with Rafters

The ridge beam should be lifted to the correct height and nailed between the centering rafters. This will provide support for the ridge beam and prevent it from collapsing. Additional centering rafters should be set in place and nailed to the walls of the structure to further support the ridge beam.

The king common rafters should be attached to the end of the ridge board to keep it steady in place. This is done by nailing one rafter on each side of the hip roof to brace the ridge board. The hip rafters should then be nailed to the ridge beam and the corners of the walls, making sure to attach a ceiling joist next to each one for extra support.

To ensure the roof is stable, the common rafters should be spaced exactly 20 inches (51 cm) from the adjacent common rafters. The common rafters and ridge beam should now stand solidly on their own.

Suggestion: Lean to Roof Rafters

Cutting the roof can be a bit tricky, but with the right tools and a clear understanding of the process, you'll be able to tackle it with ease.

To cut hip rafters, you'll need to use a different angle than a common rafter plumb cut.

The hip rafter plumb cut is a crucial part of the process, and it's essential to get it right.

You'll need to move the blade on your Stanley Quick Square to the corresponding notch for the hip rafter.

Cutting the hip rafter plumb cut requires a bit of planning, as you need to form a point on the end of the timber.

To do this, mark a plumb line on the end of the timber, making sure the bow/camber is upward.

You'll also need to mark back square from that plumb line half the thickness of the ridge, which in this case is 25mm.

This will give you the correct position for the point of the hip rafter.

With the markings in place, you can cut the hip rafter plumb cut with a circular saw, set to 45°.

The point will be where the original plumb cut was, so make sure to cut carefully and accurately.

Consider reading: Roof Truss Bracing Done Right

To create an accurate roof layout, start by laying out the lines 2 inches in from each edge of the plywood to define the outside edge of the fascia. Mark the fascia thickness and its half-width to create the plane point where the sheathing meets the fascia.

Measure back from the face of the fascia for the full overhang depth to create the plate lines representing the outside of the building. This will help you visualize the irregular roof geometry and ensure accurate angle and offset determination for complex roof sections.

For hips, start at the fascia corner's centerline, measuring distances to set the sides of the hip rafter tail. Use the plan-view drawing to determine the exact offset needed for each hip or valley rafter, finding the plumb-line shift.

Mark the birdsmouth location as well, and use the HAP of each common rafter to draw out the birdsmouth for the hip or valley rafters. Plot the tail cuts for jack and common rafters too, transferring these measurements to the actual rafters to prevent confusion later.

You might enjoy: How to Cut Rafters for a Lean to Roof

A full-scale drawing on plywood allows you to pre-mark and pre-cut parts, saving time and avoiding fixes in awkward spots. Double-check your drawn dimensions on plywood before cutting, and aligning drawings on square-edged plywood keeps every detail precise.

Here's a quick reference guide to help you visualize the roof layout:

Remember to calculate plan angles and rafter backing to ensure rafters fit snugly against the roof plane, especially critical for irregular elements like hips and valleys.

When measuring for hip roof rafters, don't forget to subtract the size of the beams to avoid hip rafters running all the way to the top of the roof. This ensures they connect properly to the ridge board.

There are four main types of rafters used in hip roofs: common, jack, hip, and ridge beam rafters. The ridge beam is a horizontal beam at the top of the roof, supported by the other rafters.

To cut roof members safely, consider cutting them on the deck before installing them. This can make the installation process much easier and safer.

For your interest: Top Wash Roof & Exterior Cleaning

To build a hip roof, you'll need some essential tools and materials. Here are the key things you'll need to get started:

A laser distance measuring device is a must-have for accurately measuring the width and height of your building. This will help you determine the right measurements for your roof.

Cutting tools like a round saw and a hammer are crucial for cutting wooden planks to size and making birdsmouth cuts. You'll also need nails to secure the rafters in place.

A carpenter's framing square is a handy tool for assembling the rafters and ensuring they're square. It's also useful for making precise cuts.

Here's a list of the materials you'll need:

A measuring tape or ruler can also come in handy for double-checking your measurements.

When building a hip roof, it's essential to remember to subtract the size of the beams from your measurements. This ensures that your hip rafters don't run from the walls to the top of the roof, but from the walls to the bottom of the ridge board.

The types of rafters used in a hip roof are quite specific. There are common, jack, hip, and ridge beam rafters, with the ridge beam running horizontally along the top of the roof and supported by the other rafters.

The 4 hip rafters start at the 4 corners of the roof and connect to the ridge beam. Common rafters, on the other hand, are the uncut, full-length rafters that provide the majority of the roof's structure and attach to the ridge board.

Here's a quick rundown of the types of rafters you'll need for a hip roof:

Finishing a hip roof requires some careful planning and execution. You'll need to nail the jack rafters to the hip rafters and secure them to the walls, spacing them out every 20 inches between the hip rafters and the king common rafters.

To determine the number of plywood sheets you'll need, measure the width and height of each of the 4 sides of the roof, then multiply the length of each side by its height to find the area. Add the areas of all the sides together to calculate the total area of the roof.

You'll need to calculate the area of one plywood sheet and divide the total area of the roof by that to figure out the number of sheets you'll need.

To nail the plywood sheathing to the rafters, start by placing a sheet in a corner and using nails to tack it in place. Make sure the first sheet is straight by tacking up a second sheet next to it, ensuring the sheets are in line with the fascia.

You'll need at least 3 packages of shingles, a roll of underlayment, and a roll of flashing to finish the roof.

Suggestion: Roll Shingle Roofing