Rafters Vs Trusses | Types of Roof Rafters | Pitched Roof Insulation Between Rafters & Trusses
Rafters vs Trusses | Difference Between Roof Rafter and Truss | Construction of a Rafter Roof | Roof Rafters Size | Benefits of Rafters Insulations
What are Rafters?
A rafter is one of a collection of sloped structural parts, such as wooden beams, that reach from the ridge or hip to the wall plate, downslope perimeter, or eave and are meant to support the roof shingles, roof deck, and the loads they support.
Rafters are the long, diagonal pieces of lumber used to create a roof. These rafters are placed at an angle to the wall and secured with nails to the top of the wall.
They are bits of wood that are shaped in a triangular pattern. These triangular shapes are put together in a skeleton frame to make the roof.
A couple is a pair of rafters. Rafters are typically built of wood in home construction. Some historic roof types include exposed rafters.
The rafters connect to each other, and in some cases, they make a triangle with a ridgeboard. The roof rafters are then connected to the wall frames on either side with a tie beam at the end. They also have the support of a collar beam on each side.
The roof rafters are usually made from a lot of 2x4s. If there is a collar beam, it will be made of 2×6 or 2×8 boards. The rafters are secured with 2x3s, 2x4s
They provide additional support to the roof framing and can be used for loads bearing. Rafters are traditionally constructed of wood, but may be constructed of other materials such as steel, aluminum, or plastic.
A rafter can be reinforced with a strut, principal purlin, collar beam, or, rarely, an auxiliary rafter.
Construction of a Rafter Roof
A simple rafter roof is made up of rafters that rest on horizontal wall plates on top of each wall. The upper ends of the rafters usually meet at a ridge beam, but they can butt straight to another rafter to form a couple of rafters.
Depending on the roof covering material, horizontal laths, battens, or purlins are attached to the rafters, or boards, plywood, or oriented strand board form the roof deck (also known as sheeting or sheathing) to support the roof covering.
To support larger rafter spans, heavier under purlins or purlin plates are used.
Tie beams, which can also function as ceiling joists, are generally attached between the lower ends of opposing rafters to keep them from expanding and pushing the walls apart.
Collar beams or collar ties can be installed higher up between opposing rafters for added strength. The rafters, tie beams, and plates transfer the weight of the roof to the building’s walls.
Types of Rafters
Principal Rafter/ Major Rafter
Normally, this rafter lands directly on a tie beam. The purpose of a larger rafter is usually to carry a purlin that supports the rafters in each bay. The top chord (uppermost member) of a truss might sometimes resemble a major rafter.
Common Rafter /Minor Rafter
A common rafter is a smaller version of a primary rafter. A “principal/common rafter roof,” sometimes known as a “double roof,” contains both principals and commons.
A secondary rafter that is located beneath and supports a major rafter. It is a unique sort of rafter.
A compass rafter is a rafter that is curved or bowed on the top (the top surface of a rafter is referred to as its “back”) or on both the top and bottom surfaces.
The upper rafters of a curb roof (kerb, gambrel, or Mansard roof).
Hip Rafter /Angle Rafter
A hip rafter is a rafter that is found in the corners of a hip roof. A hip rafter’s foot lands on a dragon beam.
The king rafter is the longest rafter on the side of a hip roof that runs parallel to the ridge.
A valley rafter is a rafter that creates a roof valley
An intermediate rafter is a rafter that connects two main or common rafters to strengthen a specific area.
Jack Rafter /Cripple-Jack Rafter
A shorter rafter, such as landing on a hip rafter or being interrupted by a dormer, is referred to as a jack rafter or cripple-jack rafter.
In an arched roof, the rafter is segmental in shape.
Knee /Cranked Rafter
A knee /cranked rafter is a rafter with a bend a few feet from the foot that is used to increase attic space, similar to adding a kneewall.
The outermost rafter on a gable end, occasionally generating a roof overhang, is known as a barge rafter.
Butt rafter is a smaller rafter that is interrupted by and connected to a butt purlin. Common rafters cross across and, if present, are supported by a primary purlin.
Roof Rafters Size
The roof rafters are the long, wide pieces of lumber that support the weight of a roof. They are also used to attach the wall plates and sheathing boards onto the top plate.
Rafters are typically constructed of pine or cedar. Building materials producers have designed LVL (Laminated veneer lumber) rafters that can be 2–5 times longer than ordinary wood rafters for greater span rafters.
Most wood rafters in the United States have a maximum length of 20 feet. If a longer rafter is required, LVL is the best combo option.
Commonly, 2x4s or 2x6s will be used for this purpose. The thickness of your rafters will depend on what you want to use them for.
For example, if you’re building an enclosed porch with a ceiling then you’ll need thicker rafters than if you were just making framing for a deck or patio cover over your existing roof.
Consider the proposed roof type and the support required – battens, purlins, or sarking – when determining rafter spacing.
Pitched Roof Insulation Between Rafters
Why do we need rafter insulation?
Insulation is important to improve a building’s energy efficiency.
When a pitched roof area is formed, the residents of loft living spaces are frequently subjected to significant levels of external noise, such as air traffic. This means that acoustic treatment of the roof is equally crucial.
A roof area can be converted into a suitable living space with proper insulation. This can be installed in several ways, and a combination of the approaches is frequently necessary to complete a project.
Benefits of Rafters Insulations
- Key Benefits of rafter’s insulations include:
- Improvements in energy efficiency and a warmer surface temperature on the interior of the outer wall.
- Improved fire safety, particularly around apertures, preventing fire from spreading through the cavity.
- Costs of heating and cooling are reduced.
- Installation is quick and simple.
Insulation in between rafters
For best performance, between-the-rafter slabs and rolls are frequently paired with under-and-over-the-rafter insulation.
Insulation between the rafters is typically used to create greater headroom between the wooden beams. Insulation is put on the inside or exterior to improve thermal, fire, and acoustic needs.
Insulation under rafters
Insulation under rafters is installed on the inside of the loadbearing structure of the roof. In addition to the insulation installed between the rafters, there is generally a few centimetres of insulation under the rafter insulation.
Insulation above the rafters
Over the rafter insulation is utilized to keep the attic area as large as possible, especially when used for dwelling.
Rafters’ insulation ensures that both heat and sound are contained effectively. It also helps to:
- Prevent heat loss
- Improve energy efficiency overall
- Increase fire safety
Rafters Vs Trusses
What is the difference between Rafters Vs. Trusses
In the construction industry, there are two main types of framing: rafters and trusses. Rafters and trusses are two different types of roof framing.
Rafters consist of a series of parallel members that extend from one end to the other.
Trusses, on the other hand, provide structural support by joining various pieces together to form triangles or squares.
The spacing between rafters is typically greater than the spacing between trusses. Rafter roofs have historically been more common in regions with heavy snowfall because they can span wider distances without collapsing under load.
Nevertheless, many people prefer truss roofs due to their inherent strength and versatility.
Rafters are the horizontal pieces that create a frame work for your roof, while trusses provide structural support to help maintain their shape.
There is no set number of rafters needed in any particular type of construction because it depends on the pitch or angle at which they meet at the peak and how wide they need to be.
Trusses come in pre-made sizes based on length, width, and depth with each size having its own weight restrictions. They also have different sizes such as 2×6 or 3×8 depending on where you live so make sure you know what size will fit best before purchasing!
A rafter is a long, narrow beam that supports the roof or ceiling of a house. It is very similar to a board, but instead of a flat top, it has a cross-shaped top called a crown or a collar.
Trusses can be the same as rafters in that they help keep the roof safe. They are built with triangles and while one side of the triangle is angled, the other is straight.
Roof Rafters FAQs
1. Should I insulate roof rafters?
When insulating the pitched section of the roof, it is best to start by insulating between the rafters, as this provides the maximum insulation space without diminishing the living area.
Furthermore, insulation can be installed below or above the rafter line, depending on local regulations and the performance desired.
2. What is the maximum span of a roof rafter?
The maximum span of a roof rafter is determined by its size, spacing, and species of wood, as well as the design stresses applied to the roof system and whether or not the ceiling is linked to the rafter.
3. What is the minimum span of a roof rafter?
The minimum span of a roof rafter is determined by its size, spacing, and species of wood. The smaller the beams, the closer they can be spaced.
4. Can I decrease my usable space to accommodate more insulation?
While it is possible to decrease your living area in order to increase the amount of insulation within your loft area, this is often not an advisable approach as it results in a less efficient dwelling and hence increased heating costs.
5. How do I insulate under the rafters?
Insulating under the between is preferable to insulating under the rafters as the latter is not possible for many loft conversions.
The main exception to this rule is when a ceiling is built directly upon the under-rafter insulation to provide greater headroom and living space.
6. What is the maximum span for a 2×6 Rafter?
There is no exact value as it will be dependent on the depth of the roof, the type of rafter, and the span. However, a 2×6 rafter is commonly used in a span of up to 18 feet.
7. What is the maximum span for a 2×10 Rafter?
There is no exact value as it will be dependent on the depth of the roof, the type of rafter, and the span. However, a 2×10 rafter is commonly used in a span of up to 30 feet.
8. What is the minimum size for a rafter?
The minimum size for a rafter is determined by its timber time species and whether or not it supports any structural loads such as ceilings.
9. What is the maximum size for a rafter?
The maximum size for a rafter is determined by its timber time species and whether or not it supports any structural loads such as ceilings.
10. Is it possible to insulate under the rafters?
Yes, although this is not advised as this reduces the usable space within the loft.
11. What is the difference between Rafters Vs. Trusses
Rafters and trusses are both wooden /steel beams used in roofing construction to span longer distances than a single timber beam, but they have different shapes and purposes.
Rafters are typically used as the main support structure on one end of a building’s roof system, while trusses are usually installed at right angles to the rafters with structural supports running perpendicular to them.
The two types also differ in that while rafter boards can be cut from long pieces of lumber like 2×4’s or 2×8’s, wood truss members come pre-formed from standard sized lumber pieces to triangular shape.