The roof is a vital part of a home and helps secure walls and keeps the elements out. It is an essential structural component of a building and usually begins with a roof framing plan. If you’re not sure what the plan is, we’re here to help.
The roof framing plan is usually a scaled drawing of the roof. It identifies the roof design, slopes, and shape with all the dimensions and measurements, as well as ventilation, drainage, wiring, and bracing placement and requirements. It helps manufacturers, and builders determine building strategies and material requirements.
In this article, we’ll explain what a roofing framing plan is and the different types and parts of roof framing. We’ll discuss different residential roof framing plans samples, and how to design a roof framing plan. Plus, we’ll identify the difference between a roof framing plan and a roof plan. Our goal is to help make your next building project easier.
- What Is a Roof Framing Plan in Construction
- Types of Roof Framing
- Parts of Roof Framing
- Residential Roof Framing Plan Samples
- How to Design Roof Framing Plan
- What Is the Difference Between Roof Plan and Roof Framing Plan?
- Online Roof Design Software
What Is a Roof Framing Plan in Construction
A roof framing plan is typically a scaled two-dimensional construction drawing or rendering of the roof framing. It identifies measurements and dimensions for the roof, shape, slope, and placement of structural components and bracing, as well as drainage, wiring, and ventilation.
Its purpose is to assist builders, manufacturers, and DIYers with material requirements, assembly, and construction. The framing plan usually includes profile renderings and top-view drawings identifying all structural components, measurements, and angles.
It is drawn in such a way that those responsible for the roof construction will know where each component for the roof framing goes and how it is assembled. It is a detailed plan or layout that shows the placement and measurements of ridge board or beam, rafters, collar ties, struts, purlins, tails, rakes, ceiling joists, girders, trusses, and other roof-related components. It can also include related building codes and fire safety requirements.
The purpose of a roof framing plan is to ensure that the roof is structurally sound and compliant with building and fire codes and regulations. It helps identify how the roof will be built, where supports will be placed, and what materials will be required.
It commonly identifies how rafters are cut, their dimensions, joints, birdsmouth cuts, placement, and supports. The roof framing plan explains how to construct the roof to give it its unique shape.
Types of Roof Framing
Roof framing is usually done using engineered trusses or dimensional lumber to build the roof, commonly referred to as stick framing. Some roofs, however, use a combination of both methods depending on the roof design and plans for attic space.
Roof trusses are a relatively recent building practice that saves both time and materials, which in the overall cost of the build, also saves money. They are computer designed and engineered to support and distribute the roof and all loads it must carry. Trusses are factory-made, so each piece is precision cut to ensure accuracy, strength, stability, uniformity, and quality. All joints are reinforced with plywood or steel gussets or connector plates.
Trusses are manufactured off-site to engineered specifications using the measurements, slopes, spans, and ceiling requirements set by the builder, architect, or designer. They commonly have a top chord that helps form the roof slope and a bottom chord that forms the ceiling – be it flat, stepped, cathedral, arched, or contains an attic. Between the top and bottom chord is web bracing that forms a series of triangles that help transfer the roof loads to the exterior or interior walls or supports.
A truss is typically fabricated from 2×3, 2×4, or 2×6 dimensional lumber and used for gable and hip roofs. Trusses can also be used for flat, skillion, and shed roofs too. Trusses are made up of various lengths of lumber laid out to form triangle web supports.
The layout of the webbing helps determine the distance trusses can span and the shape of the ceiling and roof deck. Plus, the webbing transfers the loads to support points, allowing for larger rooms or open spaces underneath.
Once manufactured, the trusses are delivered to the building site. Once the exterior walls and any interior supports are built, the trusses are then lifted and placed or slid into position.
Depending on the size and weight of the trusses, the lifting may be done using a crane, forklift, or other mechanical means, or they can be worked into position manually. Once positioned and leveled, they must be braced according to the roof framing plan, and hurricane ties or straps fastened in place.
Stick framing is done completely on-site and in place. Common dimensional lumber is cut for use as rafters, ridge boards or beams, collar ties, struts, purlins, tails, rakes, and ceiling joists. Each piece is individually placed and fastened. Stick framing is more labor and skill-intensive, takes more time, and often results in more waste. Plus, it involves more precision cuts and calculations.
The span, rise, run, line length, and pitch, are just some of the calculations that need to be done. The slope and roof shape are determined by the cut and placement of the rafters, which in turn are supported by other structural roof components. Those components must be cut and placed to provide the maximum support for the rafters and the loads they carry. Some roofs are less complex to build, but most require a lot of measuring and cuts.
The placement of the ridge board or beam determines the slope and rafter span. Each rafter has to be plumb cut at the correct angle to butt with the opposing rafter or the ridge board.
A birdsmouth also must be cut so the end of the rafter sits flush on the top plate of the supporting wall or beam. Even the tail of the rafter has to be plum cut for the fascia board. The spacing between rafters also must be factored in, and any valleys crafted too. Additionally, many codes require metal hurricane straps and ties too.
Similar to trusses, opposing rafter pairs with their collar ties and ceiling joist form triangles to move the roof load to support walls or beams. Larger roof spans often require the addition of struts and purlins to provide additional mid-span support.
Stick framed roofs have been around for millennia, and still have some advantages over trusses. Rafters allow for more customization of the roof deck and are more easily modified during the build or for future renovations.
Parts of Roof Framing
A roof framing plan may identify the placement and bracing of trusses, or it may identify the placement of all components for stick framing a roof. Some components form the slope and shape of the roof, while others provide support and ensure structural integrity.
Some of the parts are found in all stick framing, others only in certain types for roofs. Most parts of roof construction must also comply with the building code. The following definitions explain what the part is and what it does.
The ridge board appears between the plumb ends of opposing rafters to form the ridge line of the roof. It may be free-standing or supported at the ends by the gable wall. The board is used to fasten the rafters into place and to help space and align them.
It must be nominally 1” thick or greater and at least as deep as the plumb cut end of the rafters fastening to it. Ridge boards are used for 3/12 or 25% slopes or greater and must be used with ceiling joists or rafter ties. They run parallel to the exterior support walls.
The ridge beam is an engineered structural member designed to carry the weight of the roof framing, sheathing, roof finish, and all wind and snow loads. The beam is supported on end walls and/or posts and supports the ends of the rafters. Ridge beams may be used for any slope, but must be used if the slope is less than 3/12 or 25%. They too run parallel to exterior roof eaves support walls.
A common rafter runs perpendicular (90°) from the ridge board or beam to the exterior support wall. It commonly extends 12” to 24” or more beyond the exterior walls to form protective eaves or overhangs. They are used to form roof decks that run the full length from the ridge line to the exterior walls.
A jack rafter also referred to as a cripple-jack, hip jack, valley jack, or dormer jack rafter, is a short rafter. It typically runs perpendicular (90°) to the ridge plate or beam but doesn’t run the full length of a common rafter.
It is commonly used when roof planes intersect such as at a hip or valley. A jack rafter can run from the ridge to a valley rafter or hip rafter to an exterior wall, or both. It is also used when a roof plane is interrupted by a chimney or dormer.
A hip rafter runs from the end of the roof’s ridge diagonally to the top plate where two exterior walls meet to form an exterior angle. Hip rafters are used to form a hipped roof or peaked roof, or to form a hip where two roof planes meet.
A rafter that typically runs diagonally from the ridge line where two roof planes meet to where the eaves extensions meet and form an interior angle. A valley rafter may also be a short or jack rafter where a dormer roof or smaller roof intersects with the main roof deck.
A collar tie is a horizontal structural element that connects two opposing rafters and helps prevent uplift by wind loads. Collar ties are also compression connectors that help prevent the rafters from separating at the ridge due to wind or snow loads, or other downward forces.
Collar ties must be within the upper third of the rafter and should not be more than 4’ apart on center. They also need to nominally be 1”x4” lumber or greater. Collar ties are typically face nailed to the rafters.
Rafter ties are horizontal tension ties connecting opposing rafter pairs, must be no more than 4’ on center, and are located in the bottom third of the rafter. They help prevent wind thrust or uplift coming up under overhanging eaves or soffits and resist the spreading of the roof plane or bulging at the top of walls.
Rafter ties must be of 2×4 or greater lumber and are commonly face nailed to rafters. Mid-span rafter ties are located below the upper third and above the lower third of the rafter and are considered neutral or varying load support.
Purlins or under-purlins are typically used on the underside of rafters to provide additional horizontal mid-rafter span support. Purlins also help tie the rafters laterally together to improve stability and strength and help prevent sagging. They are often used to increase rafter span without the need to increase rafter depth.
Typically 2×4 or greater, they should be oriented so the narrowest dimension is against the rafters. Purlins should also provide continuous uninterrupted support under all rafters with the same orientation.
Roof struts are 2×4 or 2×6 structural members that are either vertical or perpendicular to the rafters. They are usually spaced every 48” to transfer roof or purlin loads to vertical support points or bearing walls.
The struts provide resistance to longitudinal compression and outward support along their lengthwise orientation. The closer to vertical the strut the better, however, they must be within 35° of vertical to be code compliant. Struts are spaced and commonly notched or birdsmouth to accommodate the purlin and often have a block to prevent slippage where they connect to the ceiling joist or strut beam.
The tail is the part of the rafter that protrudes beyond the exterior wall. The end is usually cut plumb and the fascia is attached. Tails are commonly an extension of the rafters but may also be added to rafters that end at the top plate. Tails form the eaves and help protect the structure from moisture damage by moving runoff away from the walls and foundation.
The rake provides both an aesthetic and functional purpose. It is the part of the roof that protrudes beyond the gable end to provide the eaves over the end walls of the structure. They help keep moisture out of the roof and end walls, and from seeping between the sheathing and siding.
The rake typically fastens to the end rafter and comprises equally spaced 2×4 lengths running perpendicular to the rafters. It rests on the gable wall top plate and protrudes 12” to 24” beyond to form an overhang. The fascia is fastened to the end of the rake boards and the soffit to the underside.
Ceiling joists are horizontal structural framing that run parallel to the rafters and usually span from the top plate of one exterior wall to the opposing exterior wall’s top plate, or to intermediate supports. They tie the exterior walls and rafter ends together and help transfer roof loads through vertical supports to the ground.
They are usually face nailed to rafters where they rest on the top plates and help prevent the walls from bowing outward or the rafters collapsing. They also provide framing for ceiling finishings and insulation.
Residential Roof Framing Plan Samples
The complexity of residential roof framing plans depends on the type or style of roof. The number of ridges and valleys, and the roof’s pitch and span all affect the amount of information required in a roof framing plan.
Roofs must be code compliant and provide strength, stability, durability, protection from the elements, fire safety, security, thermal and sound insulation properties, and aesthetics. Most roofs can be constructed with stick framing or with trusses.
Below are brief descriptions of some common roof types, including their unique framing aspects.
A roof is considered flat if its slope is within 5 degrees of horizontal. Flat roofs are easier and less expensive to build than many other roof types but also don’t last as long. One flat roof plan is to have the rafters or beams laid and spaced to span across the top plates of the two opposing exterior walls that are closest together. The rafters or beams often extend beyond the top plates to create an overhang too.
Another flat roof design is similar to the first but also has purlins spaced and attached perpendicularly on top of the rafters or beams. The purlins also extend beyond the exterior walls to create an overhang.
A flat roof may be a cold or warm roof and typically requires a waterproof membrane, or it may be a built-up roof with multiple layers of waterproofing and insulation. The flat roof is low profile and can be used for outdoor living space, solar collection, and/or garden space.
A gable roof has two angled planes or decks with a common slope running from opposing exterior walls to a raised and parallel mid-structure running ridge or peak. The complexity of the roof typically depended on the rafter span and wind and snow loads.
The slope allows the roof to shed rain and snow more easily than the flat roof but exposes it to more wind force. The slope also creates attic space which can be used for storage or living and also is easier to vent to reduce summer heat.
The gable ends are closed in with framing and usually have a ladder-like extension perpendicular to the last rafter to form a protective overhang. The roof deck is sheathed and covered with a protective moisture barrier such as tiles, shakes, shingles, or steel.
Many other roof styles also include gable roof construction. Traditionally a budget-friendly stick frame design, they are commonly built with trusses today.
A shed roof is similar to a flat roof except it is elevated at one end of the rafters. Thus, the building typically has one taller wall opposite a shorter wall. The distance between the supporting walls and the height difference between them determines the single roof plane’s slope.
The rafters span the distance between supporting walls and typically extend beyond the lower wall further than they extend past the higher wall. The end walls often don’t have much if any overhang and require flashing to prevent moisture damage.
A common way to protect the end walls is to construct a ladder rafter that extends over the wall from the last rafter. This helps to shed snow and rain further away from the base and walls of the structure.
A shed roof is usually supported on only the exterior walls which often limited the width of the structure as the rafter span is limited to the strength of the timber. Thus, the roof design was frequently used for sheds or outbuildings. However, they became more common for residential and commercial structures as construction techniques and materials increased the span distances significantly without the need for interior support walls or beams.
A shed roof is often called a skillion, lean-to, pent roof, or a mono-pitch roof. However, a skillion roof has a higher slope than typical shed roofs and a lean-to is usually attached to an existing structure and uses it as one of its support walls.
A hip roof is often used to protect a rectangular or square-shaped building. The roof design has four roof planes, two triangular and two trapezoidal. The trapezoidal roof sections extend upward from parallel exterior walls and meet at a raised horizontal ridge beam or board. Although the ridge is parallel to the walls, it doesn’t extend the full distance.
Hip rafters are used to connect the ends of the ridge with the four corners of the dwelling, thus forming the two triangular roof planes. Jack rafters are used to fill in the roof plane between the four hip rafters.
Hip roofs can also be comprised of four triangular roof planes that meet at a point instead of a ridge. Both styles provide overhanging eaves which protect the exterior walls and foundation.
Hip roofs are also commonly called cottage roofs as their eaves often extend outward to cover porches or decks. However, if the deck is covered with jack rafters angled at a lesser slope, the design is referred to as a witch’s hat. Hip roof designs are also frequently blended with gable roof designs.
A skillion roof, although similar to a shed roof typically has a more significant slope. Believed to have originated in Australia, the minimalistic design jumped continents and became popular in midcentury modern construction and is still popular today. The long single-sloping roof plane often extends beyond both supporting walls and end walls to provide shade and help shed snow and rainfall.
The roof design has few structural components so can be erected fairly quickly with trusses or stick framing. It offers a longer lifespan, energy efficiency, and affordability. The higher wall provides greater potential for glazing and natural lighting and is often used for lofts to extend living or storage space.
The long slope not only sheds moisture well but can be personalized with skylights or shed windows for additional lighting. Today, the slope is commonly seen supporting arrays of solar panels and even collecting rainwater for gardens and household use.
How to Design Roof Framing Plan
Designing a roof framing plan typically begins by selecting the style of roof and whether it will be stick framed or truss. Once those two hurdles are passed, determine the span, rise, run, pitch angle or slope, line length, and overhang or soffit distances. The overhang projection, although not typically structural is important for the design.
The span is the distance from one exterior wall to the opposing exterior wall upon which the roof will sit. The rise is the height of the top of the ridge line, and the run is determined by dividing the span by two – provided the ridge will be at the center of the building.
The pitch is the angle created by the rafter between the top of the wall and the ridge height, also measured as the slope based on the rise per unit of run. The line length is the diagonal length of the rafter from the center of the ridge to the outer edge of the support wall.
For example, the distance between walls may be 20’, which produces a run of 10’ (120”) when divided by 2. The rise can be determined by the elevation required at the ridge to ensure sufficient attic space, or it can be determined by the rise over run or pitch angle.
If the roof slope desired is 3:12 or 3/12, then it will rise 3” for every 12” of run. So, for the 10 units of run, it will rise (3×10) 30”. A 3/12 slope produces a 14.04° angle of pitch. The line length can be calculated using the Pythagorean formula of a² + b² = c², where a is the rise, b is the run, and the root of c is the line length. So, 30² + 120² = √15,300 = 123.7”
The next step is to draw the roof framing plan with all building components to ensure that it is structurally stable and code compliant.
What Is the Difference Between Roof Plan and Roof Framing Plan?
A roof framing plan shows all measurements, the outline and shape of the roof, plus the size of framing components and their orientation or direction. It is a 2-D top view and profile renderings that include all framing materials used to create the roof and ceiling. It often includes notes about sheathing, weather protective membranes, shingles, tiles, or steel finishing, and even insulation requirements.
A roof plan typically is a 3-D drawing or birds-eye view showing the shape of the finished roof. It often includes the location of exterior HVAC and plumbing components, any roof access points, and what the finished roof could or should look like.
Online Roof Design Software
There are numerous roof design software programs available online or that can be purchased at different stores. Some are easier to use than others but often require some computer skills and also a basic understanding of how to build a roof.
Roof design software usually isn’t free and while most work with Windows, many aren’t Apple friendly or app supported. Additionally, most are strictly roof plan oriented and don’t provide a roof framing plan.
Those that do provide roof framing plan options typically rely on standard stick framing plans and are difficult or impossible to customize. Plus, they don’t include all structural components such as purlins, struts, and rakes.
If you’re looking for something to take to the building inspector or to hand to a builder, you should go the old-fashioned way and have the framing plan done by a pro.
A roof framing plan is a scale 2-D rendering or drawing of the structural components of a roof. It includes all dimensions and identifies the roof shape, design, and slopes. It shows the placement and direction of trusses or rafters, purlins, collar and rafter ties, struts, tails, rakes, and even ceiling joists.
It also often notes hurricane ties, sheathing, insulation, waterproof membrane, and type of roof finish. It helps manufacturers, contractors, and carpenters determine material requirements and building strategies to make the roof structurally sound and code compliant.
Hopefully, you have a better awareness of what a roof framing plan is and its importance.