When it comes to modular building construction in NZ, the two most common framing materials are steel and timber. Both materials have their unique advantages and disadvantages, making it essential to weigh them against each other. In this article, we will compare the use of steel frame vs timber frame in modular buildings to help you make an informed decision for your next construction project.
Strength and durability
One of the most significant benefits of steel frame buildings is their superior strength-to-weight ratio over timber. This is hugely advantageous in prefabricated buildings, as weight is a key factor when considering the feasibility of a project and the machinery required to move and lift buildings into place.
Additionally, steel is a tough and robust material that can withstand extreme weather conditions, such as heavy rain and high winds. It is resistant to rot, termites, and other pests, providing that it is properly enclosed from the elements –– this makes steel a maintenance-free material, with no need for pest or mould treatment. If the steel framing is not properly enclosed, however, trapped water can lead to rusting which can impact the structural integrity of a building over time.
Timber frame buildings have a proven track record and have stood the test of time in New Zealand’s harsh weather conditions. However, they do not compare to the strength and durability of steel frame buildings. Although timber has natural strength, it’s not as robust as steel, making it susceptible to warping and twisting over time. Additionally, timber is prone to damage from pests and rot, which can shorten its lifespan if the correct treatment is not used.
Usability
Due to the light weight of steel frames, they can be installed faster than timber and using less personnel. However, one of the biggest disadvantages when using steel framing is the difficulties associated with changing frame patterns. For example, if you wish to change the position of a window, this process is more difficult than with timber framing which is very forgiving and easy to work with. A wider range of power and hand tools currently make working with timber a preferred choice for New Zealand builders, however steel is becoming more popular year by year.
Environmental impact
The environmental impact of a building is an increasingly important factor to consider in construction projects. Steel frame buildings are not considered to be as eco-friendly or sustainable as renewable timber frame buildings, as steel production is an energy-intensive process and the material itself is not biodegradable. However, steel is 100% recyclable, significantly improving its environmental impact.
In contrast, timber frames in New Zealand are considered to be environmentally friendly as they are made from local renewable forests. There is still a downfall of timber to consider, though. When it comes to disposing of framing during construction, later maintenance or at the end of a building’s life, the chemicals used to treat the timber can release toxic contaminants when burnt or buried. This can affect people who drink contaminated water from the water table.
Design benefits
Due to steel’s superior strength and rigidity, it is generally a preference for engineers when designing more complex structures. This is because it can span longer distances and support more weight in comparison to timber. This benefit makes it popular in modern contemporary designs, where a less bulky, simple structure is desired.
Another benefit of steel framing is its ability to incorporate wall bracing within the framed studs. This is completed during the pre-nail process, eliminating the need to fix ply or gib brace linings to the face of the framing itself. It also reduces the need for a council bracing inspection, as this can be done during the framing inspection.
One area of the building that should be considered carefully when designing your building is the subfloor. Every prefabricated building’s subfloor will require bearers and floor joists that rest on piles when delivered to site. The advantage of choosing timber for the subfloor is that the timber under the building can remain exposed to the elements and not deteriorate over time. When using steel, on the other hand, the entire subfloor must be closed in to stop moisture from pooling in the C channel-shaped member and causing it to rust.
Another disadvantage with steel is that sloping floors cannot be recessed into steel members as they can with timber. Tile showers are a prime example of this, where you can check out the timber floor joists to create the fall required.
In addition, steel framing is harder to insulate as it is a natural conductor. In order to mitigate this issue, a thermal break between the steel framing and cavity battens is required. This adds another step onto the insulation process of steel frame buildings. Timber, on the other hand, requires no additional insulation requirements.
Fire resistance
One more aspect to consider when deciding between steel and timber frame buildings is the fire resistance of the two materials. The fire resistance of a building’s structure and its surfaces are becoming increasingly scrutinised by local legislation, and must be considered when designing your home. Steel framing offers a far superior fire resistance over timber, which is considered combustible. Not only does the building structure stand more chance of surviving a fire outbreak, it also allows more time for the building occupants to escape the building.
Steel frame vs timber frame: in conclusion…
In the world of modular buildings, both steel and timber frames have their unique advantages and disadvantages. Steel frames are stronger, more durable, and quicker to construct, while timber frames are a more sustainable, adaptable, and easier to work with. With this in mind, there is no reason why a mixture of the two products cannot be used to create your dream build.
Got any questions about modular buildings or want to discuss your next construction project? Get in touch with our team today.
