8 Common Pitched Roof Trusses and the Best Way to Select Them

When designing a building, one of the most important structural components to consider is the roof truss. For pitched roofs, trusses offer a strong, economical, and efficient solution to support roofing materials while spanning long distances without the need for internal supports. In this article, we will explore the most common types of pitched roof trusses, their characteristics, applications, and why they are widely used in residential and industrial construction.

What Is a Pitched Roof Truss?

A pitched roof truss is a prefabricated structural framework designed to support a sloping roof. It transfers the roof load to the building’s exterior walls, providing stability and strength. Unlike flat roof trusses, pitched roof trusses have an inclined profile, making them ideal for regions with heavy rainfall or snow.

Chord members of these trusses that are adjacent to the supports experience fewer axial forces as well as secondary stresses. The bottom chord can be provided with a camber; the slope of the bottom chord may be kept equal to half the slope of the top chord for optimum design.

Again, going further, based on pitch, the trusses may be divided into three categories:

1. Small pitch–span depth ratio of more than 12.
2. Medium pitch–span depth ratio between 5 to 12.
3. Large pitch-span depth ratio of 5 or less.

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Types of Pitched Roof Truss

Several types of pitched roof trusses, originally developed for bridge engineering, are now widely adopted in building construction due to their structural efficiency, aesthetic appeal, and ease of fabrication and installation.

1. King Post Truss
2. Queen Post Truss
3. Fink Truss
4. Howe Truss
5. Pratt Truss
6. Fan Truss
7. North Light Truss
8. Belgian Truss

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King Post Truss

The king-post truss is one of the most common and simplest types of roof trusses, typically used for short-span structures. It consists of a central vertical post, called the king post, supporting two inclined rafters on either side to form a pitched roof. Traditionally, the king post is made of heavy timber, and some argue that if a steel rod is used in its place, the truss is no longer considered a true king-post truss.

Key Feature:

• Small buildings with a roof span up to 6m.
• Traditional timber construction

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Queen Post Truss

This truss extends the concept of the king-post truss by incorporating two vertical posts instead of one, enabling it to span comparatively longer distances. These vertical members are known as queen posts, which are often connected at the top by a horizontal straining beam or frame. The rafters are inclined on both sides, forming a pitched roof profile. Unlike the king-post truss, the queen-post truss does not have a central principal post.

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Fink Truss

The Fink truss is one of the most widely used roof trusses in residential and light commercial construction, characterised by its distinctive “W” pattern formed by the web members. Originally developed for bridge structures, its use in bridges has now largely diminished, while it remains popular in building construction due to its structural efficiency and ease of fabrication.

They are usually used for Residential house roofs, Light commercial buildings, Warehouses or agricultural buildings, Prefabricated truss systems, etc. The advantages of this roof type are a High strength-to-weight ratio and are Ideal for steep and moderate roof pitches. However, it is not suitable for very large spans unless modified.

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Pratt Truss

A Pratt Truss resolves the need for triangulation through the combination of diagonal members in tension and vertical members in compression. It is a truss system where Diagonal members slope towards the centre of the span or down toward the midspan. The vertical members are always in compression, whereas diagonal members handle tension under typical gravity loads.

Fan Truss

A Fan Roof Truss is a type of pitched roof truss where the web members spread out (or “fan out”) from the bottom chord toward the rafters, resembling the shape of an open hand-held fan. It is commonly used for medium spans and provides efficient load distribution with a visually clean internal layout.

A Fan Truss can be defined as a modification of the Fink truss in which the large triangular panels are subdivided into smaller triangles by introducing additional intermediate struts. These struts “fan” out from the bottom chord to the rafters, improving the structural efficiency.

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Comparison between Fan Truss and Fink Truss

Feature	Fan Truss	Fink Truss
Web pattern	Multiple “fan” members	W-shaped web
Efficiency	Higher for medium spans	High for moderate spans
Complexity	Slightly higher	Simpler
Best use	Workshops, larger roofs	Residential roofs

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North Light Truss

A North Light Truss is a pitched roof truss designed with one longer roof slope and one shorter, steeper glazed slope. The shorter slope faces north (in the Northern Hemisphere), allowing soft, diffused natural light to enter the building. It is also known as a saw tooth truss.

Key Features:

• Asymmetric shape: one long slope + one short glass panel slope.
• Glazed north-facing side: made of glass or translucent material.
• Provides natural daylight: ideal for workspaces that need consistent lighting.
• Reduces heat gain: north-facing light is diffused and cool.
• Steel truss framework: often built using steel angles or tubular sections.
• Typically used for large spans in industrial buildings, 10–30 meters.

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Belgian Truss

A Belgian Roof Truss is a traditional roof truss system commonly used in industrial and agricultural buildings. It is known for its polygonal (multi-segment) top chord and efficient use of internal tension members, making it suitable for large spans while using less material compared to heavy timber trusses. The web system includes tension rods and compression struts arranged to efficiently transfer loads.

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Factors Affecting the Selection of Roof Truss

All above mention pitched roof truss are structurally

1. Span of the Building:

The span of the building is one of the most important factors in selecting a roof truss. For short spans, trusses like the King Post, Queen Post, or Fink Truss are commonly used. For medium spans, Fan, Howe, or Pratt Trusses are more suitable. For large spans, Warren, North-Light, or Belgian Trusses are generally preferred.

2. Roof Pitch / Slope:

The pitch or slope of the roof plays a key role in selecting a truss. For steeper roofs, Fink, Howe, or Fan Trusses are commonly used, while for low-pitched or nearly flat roofs, Warren or Pratt Trusses are more suitable.

Pitch Category	Range of Pitch	Truss
Steep Roof	≥ 30° (or rise/run ≥ 1:2)	Fink, Howe, Fan
Moderate Roof	15°–30° (or rise/run ~ 1:4 to 1:2)	Pratt, King Post
Low-Pitched / Flat Roof	≤ 15° (or rise/run ≤ 1:4)	Pratt, or flat steel trusses

3. Type of Building:

The type of building significantly influences the choice of roof truss. For residential buildings, lightweight trusses such as Fink or Fan Trusses are commonly used. In industrial buildings, long-span steel trusses like Pratt, North Light, or Howe Trusses are preferred. For warehouses and workshops, trusses such as North Light, Saw-Tooth, or Pratt Trusses are most suitable.

4. Roof Coverings Materials:

The type and weight of roof covering affect truss selection. Heavy materials like tiles or slate need stronger trusses (e.g., King Post, Queen Post), while lightweight sheets allow longer spans with simpler trusses (e.g., Fink, Fan, or steel Pratt trusses). The truss design must also consider installation requirements and durability of the covering.

Also, Read: The Benefits of Tile Roofing: A Stylish and Durable Option for Your Home

5. Aesthetic Considerations:

The appearance of the roof truss can influence its selection, especially when the trusses are visible. For halls or large open spaces where the trusses are exposed, Howe, or custom steel trusses are often chosen for their structural elegance. In residential buildings where the trusses are hidden, simpler designs like Fink or Fan Trusses are preferred.

5. Climatic Considerations

The local climate is an important factor when selecting a roof truss, as it affects both the structural performance and durability of the roof.

• Wind Load: In areas with high wind speeds, trusses must resist strong lateral forces. Steel trusses like Pratt, Warren, or North Light are preferred for industrial buildings in windy regions.
• Snow Load: Regions with heavy snowfall require steeper roof slopes so that snow slides off easily. Trusses such as Fink or Howe are suitable for such conditions.
• Rainfall & Drainage: High rainfall areas need roofs designed for efficient water runoff. Steep-pitched trusses help prevent water accumulation and leakage.
• Temperature & Humidity: Timber trusses may degrade in humid or wet climates, whereas steel trusses with proper anti-corrosion treatment provide better durability.

Cost and budget, ease of fabrication and erection, and ventilation and lighting requirements are additional factors that can influence the selection of a roof truss, although they are generally less critical compared to primary factors like span, material, and roof pitch.

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FAQs

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