The Truth About Trusses
A guide to the structural frameworks that will help keep a roof over your head
Rebecca Gross
2 July 2015
Design writer and historian. I write about contemporary architecture and design, and I study cultural history through the lens of architecture, design and visual culture. I have a Masters in the History of Decorative Arts and Design from Parsons The New School for Design, New York. My latest book is called "Ornament is not a crime: Contemporary Interiors with a postmodern twist."
Design writer and historian. I write about contemporary architecture and design,... More
A truss is a structural framework designed to bridge the space at the top of a room and to provide longitudinal support for a roof. Beyond being important to a building’s construction, trusses can be show-stopping architectural features. If your trusses are hidden from view with a ceiling, then you needn’t give the look of them a second thought. However, if you’re all for exposing your trusses, then form, material and colour will play a part in how the truss will look. This will create harmony between the roof truss, the building structure and the interior of the room.
Architectural trusses add interest, detail, texture and colour to an area or space of a room that would otherwise be empty and could possibly feel barn-like. So, let’s raise the roof for exposed architectural trusses.
Architectural trusses add interest, detail, texture and colour to an area or space of a room that would otherwise be empty and could possibly feel barn-like. So, let’s raise the roof for exposed architectural trusses.
WHAT IS A TRUSS?
Trusses are frameworks of timber, steel or a light alloy comprised of independent parts. A truss has two main elements:
Trusses are frameworks of timber, steel or a light alloy comprised of independent parts. A truss has two main elements:
- Chords: the outer shape of the truss defined by the principal rafters (upper outer beams) and tie-beams (lower outer beam).
- Webs: the interior elements of the truss defined by the arrangement of the posts (vertical inner elements) and struts (angled inner elements).
HOW DOES A TRUSS WORK?
Simply, a roof truss takes the weight of the roof and efficiently transfers it onto the load-bearing walls of the house. It relies on tension and compression, and usually takes the form of a triangle or a combination of triangles to ensure maximum rigidity. The forces encountered are applied at the triangle’s joints.
In this image, the two angled chords connect the roof rafters and the ceiling joists, and work to spread the load between the rafters and the joists. The webs, or interior posts and struts, come in a myriad of arrangements to provide additional reinforcement.
Simply, a roof truss takes the weight of the roof and efficiently transfers it onto the load-bearing walls of the house. It relies on tension and compression, and usually takes the form of a triangle or a combination of triangles to ensure maximum rigidity. The forces encountered are applied at the triangle’s joints.
In this image, the two angled chords connect the roof rafters and the ceiling joists, and work to spread the load between the rafters and the joists. The webs, or interior posts and struts, come in a myriad of arrangements to provide additional reinforcement.
SOME CONSIDERATIONS WHEN DECIDING UPON ROOF TRUSSES
- The exterior roofline will influence the form and pitch of the trusses.
- The interior style of your home will influence both the form and material of the trusses used.
- The arrangement of the chords and webs will depend on both structural efficiency and building costs.
Ideas for your ceiling
10 TYPES OF ARCHITECTURAL TRUSSES
1. Pitched truss or common truss
The first four trusses listed here are all variations of the pitched truss, which is the most common form of these structures. It is characterised by a triangular shape, which may or may not have web members.
In this high-ceiling room, a simple pitched truss has been painted a mint green to add a pop of colour and interest to the upper portion of the room. Its colour ties it in with the similarly toned and colourful furnishings and decor.
1. Pitched truss or common truss
The first four trusses listed here are all variations of the pitched truss, which is the most common form of these structures. It is characterised by a triangular shape, which may or may not have web members.
In this high-ceiling room, a simple pitched truss has been painted a mint green to add a pop of colour and interest to the upper portion of the room. Its colour ties it in with the similarly toned and colourful furnishings and decor.
2. King post truss
The king post truss is another simple truss with a central vertical post (known as a king post). As there is only one post, it is placed under quite a lot of tension and is therefore better suited to narrower rooms.
The king post truss pictured here is made from tubular alloy, which is in contrast to the country cottage feel of the house. However, painted white, it complements the furniture, walls and window frames.
The king post truss is another simple truss with a central vertical post (known as a king post). As there is only one post, it is placed under quite a lot of tension and is therefore better suited to narrower rooms.
The king post truss pictured here is made from tubular alloy, which is in contrast to the country cottage feel of the house. However, painted white, it complements the furniture, walls and window frames.
3. Palladian truss
Italian architect Andrea Palladio was a big fan of using trusses, and the Palladian truss, which bears his name, is very similar to the king post truss but has web elements that radiate from the bottom of the central post like a star-burst.
The open-plan space here serves as a living-dining-kitchen area. Its metal vaulted roof makes it feel barn-like. Simple king trusses help to enclose the feeling of the space without actually reducing the size of its volume.
Italian architect Andrea Palladio was a big fan of using trusses, and the Palladian truss, which bears his name, is very similar to the king post truss but has web elements that radiate from the bottom of the central post like a star-burst.
The open-plan space here serves as a living-dining-kitchen area. Its metal vaulted roof makes it feel barn-like. Simple king trusses help to enclose the feeling of the space without actually reducing the size of its volume.
4. Tri-bearing roof truss
Another variation of the common pitched truss is the tri-bearing roof truss, which incorporates an additional upright post on either side of the king post. With three bearing points, these trusses are usually larger and able to hold a greater load.
In a wider room, this tri-bearing roof truss is an efficient way to support the roof. Spanning the space above the kitchen, each element is quite chunky, but painted, it still has a feeling of lightness.
Another variation of the common pitched truss is the tri-bearing roof truss, which incorporates an additional upright post on either side of the king post. With three bearing points, these trusses are usually larger and able to hold a greater load.
In a wider room, this tri-bearing roof truss is an efficient way to support the roof. Spanning the space above the kitchen, each element is quite chunky, but painted, it still has a feeling of lightness.
5. Queen post truss
Moving on from the simpler trusses to some more complex arrangements, the queen post truss can span wider distances due to the placement of the posts. The queen post truss does not have a central vertical post; rather it has two uprights placed to each side of the centre that are connected by a tie-beam at the top. This creates an open rectangular form in the centre of the truss.
This house combines both rustic and industrial materials and design details, and incorporates steel queen post trusses that are a fitting contrast to the timber ceiling.
Moving on from the simpler trusses to some more complex arrangements, the queen post truss can span wider distances due to the placement of the posts. The queen post truss does not have a central vertical post; rather it has two uprights placed to each side of the centre that are connected by a tie-beam at the top. This creates an open rectangular form in the centre of the truss.
This house combines both rustic and industrial materials and design details, and incorporates steel queen post trusses that are a fitting contrast to the timber ceiling.
6. Compound truss (king and queen)
When the king post truss and queen post truss are combined, the result is a compound truss, which has a king post above the upper tie-beam.
These compound trusses add another design detail to truss structures – in this case, black metal rods close the horizontal chord. This ties in with the use of metal and timber used throughout the interior and exterior of this particular home.
When the king post truss and queen post truss are combined, the result is a compound truss, which has a king post above the upper tie-beam.
These compound trusses add another design detail to truss structures – in this case, black metal rods close the horizontal chord. This ties in with the use of metal and timber used throughout the interior and exterior of this particular home.
7. Parallel chord truss or flat truss
The parallel chord truss or flat truss gets its name from its parallel upper and lower chords. It is used to support a flat roof or upper floor. Additionally, the web arrangement creates a strong geometric pattern.
The industrial shed conversion seen here makes use of existing trusses, even drawing attention to them by contrasting their black finish against white walls.
The parallel chord truss or flat truss gets its name from its parallel upper and lower chords. It is used to support a flat roof or upper floor. Additionally, the web arrangement creates a strong geometric pattern.
The industrial shed conversion seen here makes use of existing trusses, even drawing attention to them by contrasting their black finish against white walls.
8. Half truss
A half truss is a normal pitched truss that has been sliced at the apex and may have some form of web arrangement.
This elegant home is a heritage-listed chicory kiln converted into a family residence. Joinery is an architectural feature throughout the house with high timber beams and trusses on permanent display.
A half truss is a normal pitched truss that has been sliced at the apex and may have some form of web arrangement.
This elegant home is a heritage-listed chicory kiln converted into a family residence. Joinery is an architectural feature throughout the house with high timber beams and trusses on permanent display.
9. Monopitch truss
The monopitched truss is like the half truss but without webs and is often used for lean-to roofs.
The architect literally raised the roof on this house adding clerestory glazing between the elevated roof and existing wall. Timber trusses, reclaimed from the original roof, have been used to support the roof and bridge the additional upper space.
The monopitched truss is like the half truss but without webs and is often used for lean-to roofs.
The architect literally raised the roof on this house adding clerestory glazing between the elevated roof and existing wall. Timber trusses, reclaimed from the original roof, have been used to support the roof and bridge the additional upper space.
10. Scissor truss
The scissor truss is an open truss with no lower tie-beam. It gets its name from being shaped like a pair of shears or scissors, with the two lower and intersecting chords being the defining feature.
This scissor truss adds interest and detail to a vaulted ceiling while accentuating the sense of height and feeling of spaciousness.
TELL US
Does your home, apartment or studio feature timber or metal trusses? Tell us about what kind they are in the Comments.
MORE
Vaulted Ceilings: Are They Right for Your Next Home?
6 Australian Homes That Show Some Spine
Factory-Fitted: Best Warehouse Conversions From Melbourne to NYC
The scissor truss is an open truss with no lower tie-beam. It gets its name from being shaped like a pair of shears or scissors, with the two lower and intersecting chords being the defining feature.
This scissor truss adds interest and detail to a vaulted ceiling while accentuating the sense of height and feeling of spaciousness.
TELL US
Does your home, apartment or studio feature timber or metal trusses? Tell us about what kind they are in the Comments.
MORE
Vaulted Ceilings: Are They Right for Your Next Home?
6 Australian Homes That Show Some Spine
Factory-Fitted: Best Warehouse Conversions From Melbourne to NYC
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Yes, trusses are such understated elements of buildings in Australia except for earlier buildings like The Rocks warehouses as example. We utilised the benefits of King Post trusses in our own home as it suited the post and beam construction and gave us the warmth (in natural Blackbutt timber) we were looking for. By using twin bottom chords, we were able to conceal our general lighting and reflect the light from the ceiling for a softer effect.
Pic by Saul.
Is it possible to remove a ceiling and expose existing trusses or replace with architectural beams in a 8 by 10 metre room for under $30000 in Brisbane (skillion roof)
a picture is worth a 1000 words. But which? A simple diagram would save me having to read the specifications here. I gave up to write you editors this advice.