Challenges and Solutions in Constructing Hip Roofs with Light Gauge Steel
Constructing hip roofs is one of the most challenging aspects with light gauge steel construction, and is an area that timber frame installers often struggle with when transitioning to light gauge steel framing.
The primary challenges often involve correctly positioning trusses and rafters to ensure the proper formation of the hip end, ensuring straight alignment of all members along the eaves line, establishing a well-defined hip line that aligns with hip flashings, allowing ample space on the hip line for securing roof battens, and addressing difficulties in connecting members at 45-degree angles.
The ENDUROFRAME®️ building system offers a range of unique features within light gauge steel framing to effectively address the challenges associated with hip roofs. Moreover, it provides a plethora of options to accommodate diverse requirements and building practices across Australia.
When combined, these elements offer a straightforward solution for constructing hip roofs:
1. Locating holes for Truss to rafter connection
To simplify the positioning process, locating holes are punched in both the rafter and truncated truss top chords, ensuring their precise alignment as depicted in the cross-section below.
2. Truss connection details printed on wall top plate
Both trusses and rafters are accurately positioned along top plates, as their locations and associated tiedown brackets are clearly marked on top plates.
3. Locating holes for tiedown bracket to truss/rafter connection
Locating holes in tie-down brackets and truss bottom chords guarantee consistent overhangs for all rafters and trusses.
4. Folded tabs for truss/rafter to hip rafter connection
Lastly, members can be effortlessly connected using engineered folded tabs with specified capacities.
Why do we have many different ENDUROFRAME® hip options?
To ensure that steel frame technology can accommodate buildings of varying complexity and architectural style, it is crucial to have flexible options for constructing hip roofs. Builders often have their own preferences based on past experience building hip roofs and material-saving considerations.
To address this complexity, ENDUROFRAME® now offers 4 types of hip ends and 3 types of hip rafters which make up the hip roof.
It is easy to select these in the ENDUROCADD®️ software which automates the modelling and design of the trusses, rafters and brackets that make up the roof hip.
What are hip ends and hip rafters?
Hip ends refer to the options available for building common rafters or trusses that run perpendicular to the eaves and main roof trusses. These hip ends become shorter in length as they approach the corner of the roof.
Hip rafters, on the other hand, are diagonal members that extend from the corner of the roof up to the ridge line of the building. There are two main varieties of hip rafters: those centered on the hip line of the roof and those with the top flange parallel to the roof hip face.
Which hip end and hip rafter should you use?
The choice of hip options depends on job specifications, engineering requirements, and installer/builder preferences. Engineering requirements may include:
Roof pitch: Shallow roof pitches may require a larger setback for the first truncated truss, making it taller and stronger, which in turn affects the span of the hip rafters.
Heel depth: High heel depths over the external wall can impact the design of the hip rafters, potentially requiring an upstand and bottom chord trimmer.
Eave overhang distance: Larger eave overhangs may necessitate higher base material thicknesses or boxed hip rafters for increased strength.
Wind Speed: Higher wind speeds may require additional tie-downs for the hip rafters, and sometimes even thicker gauges of steel to be used, or more boxing of members.
Builder preferences often depend on their experience with previous truss systems, aiming to minimize the learning curve. For example, some builders prefer hip rafters centered on the hip line as they provide a clear indication of where the hip capping should be installed. Others opt for hip rafters in line with the hip roof face to provide a good fixing surface for roof battens.
Hip End Types
The ENDUROFRAME®️ system has 3 types of hip ends: Type 1, Type 1A, Type 2, and Type 3. This explains each of them.
Type 1 Hip End
This is the most affordable option as it uses the least amount of steel. The common rafter can be single or boxed for additional strength. It also features smart rafter holes that align with prepunched holes in the truncated truss top chords, ensuring perfect alignment of the common rafters on both trusses and the wall panel. However, this type is not recommended if there is a raised heel in the roof trusses, as it lacks a bottom chord trimmer to accommodate the heel step up over the external wall.
A 3D model for closer inspection can be found here:
Type 1A Hip End
Similar to Type 1, this hip option includes a vertical chord joining to the first truncated truss and a horizontal bottom chord running perpendicular to the first truncated truss out to the external wall.
The first truncated truss is automatically made flush to prevent clashes between the rafters and the webs of the truss. This design facilitates easy packing, storage, and transport.
Type 1A hip enables fast and accurate erection as the vertical chord on the rafter locates and braces the position of the first truncated truss. It also allows for pushing the pitching perimeter outwards to change the heel depth over the external wall and create a sail over or cantilevered eave.
A 3D model for closer inspection can be found here:
Type 2 Hip End
These rafters are exceptionally strong and ideal for large spans. The first truncated truss can be installed at a greater distance back from the pitching perimeter, providing increased strength. They are particularly suitable for raised ceilings and commercial buildings with box gutters. Type 2 hip is also the strongest option for cantilevered eaves.
The rafters are designed as trusses in the web editor and connect to the first station girder truss, which is set back by the user-defined distance.
A 3D model for closer inspection can be found here:
Type 3 Hip End
The Type 3 Hip End is the most similar method to that used by timber roof trusses in hip ends, and is ideal for builders transitioning from putting up timber trusses. It has trusses running 45 degrees from the corner of the roof resting on girder trusses with top chords extending to the apex of the roof.
This option is suitable for very low roof pitches and also where the eaves are cantilevered past the outside of the building, and can even allow boxed gutters to be included in the hip end.
This system includes a unique, innovative system of engineered tabs which can be easily folded to fixed to adjoining members making assembly quick.
A key feature of this truss system is that all members are engineered.
A 3D model for closer inspection can be found here:
What are the different Hip Rafter Types?
1. Centered Boxed Hip
This is the most common hip rafter used by Enduroframe licensees. Boxed Hip rafters are boxed sections that run along the entire hip line of the roof from the eave line to the apex point of the hip. A 50mm gap between a pair of hip rafters may be made to allow for a crown rafter to fit in between.
2. Veed Hip
Veed hip rafters are short v-shaped hip rafters made using standard sections (U, C, and Topspan 22) that run along the hip line over at least one truncated truss. They have four creeper rafters attached and are designed as left and right sections to facilitate nesting against the horn of the truncated truss. Can either be pre-made and kept in stock or made with the job when selected in ENDUROHUB®️.
3. Boxed Hip
The option has a boxed member which is offset from the hip line and is parallel with the hip face, with a secondary member on the roof face extending from the eave to the 1st station truncated truss.
4. Trussed Hip
Hip truss rafters are flush trusses constructed from the same sections as common rafters that run along the hip line from the eave to the first truncated truss.
More detailed information on all these hip types can be found at How to select rafters for your job, Hip Ends Types and Hip Rafters – ENDUROCADD Help – Confluence (atlassian.net)
