Remote housing – engineering for durability
The Insight
After decades of remote housing programs, one of the greatest challenges continues to be durability of the housing stock. Multiple factors can impact the longevity of constructed houses including:
A desire to use light-weight construction methods to lessen material and transportation costs
Less construction oversight which can lead to quality issues including improper tanking of wet areas and lower quality materials
Harsh environmental conditions – particularly true in the NT where a large proportion of houses are located in tropical, coastal, cyclonic areas
Cost and availability of reactive and planned maintenance
Based on inspection of over 200 remote dwellings, it is clear there are engineering changes that can be made which will greatly improve durability. This is particularly true in the use of cold-formed steel sections which are used as joists, bearers, purlins, battens, wall framing and other structural elements. An understanding of protective coatings and the effect of cross-section shape a crucial starting point to providing a durable end product.
The Impact
Cold-formed steel sections are commonly believed to be adequately protected by their standard zinc coating but this is 2.5 to 4 times thinner than hot-dipped galvanising resulting in relatively minimal protection. Breaching of this coating can lead to rapid deterioration in these typically thin-walled structural elements. For adequate protection, consideration must be given to additional protective coatings and / or physical protection, such as use of eaves linings to protect exposed light-gauge roof framing elements.
Light gauge cold-formed sections are typically lipped, with the bottom flange providing the perfect spot for the water to mix with various contaminants, ultimately leading to corrosion. The use of these as joists and bearers is a recipe for disaster for wet area floors and verandahs where the substructure is frequently wet. It is not uncommon to find bottom flanges of joists completely rusted away, significantly affecting structural performance.
The use of hollow steel sections can greatly increase the longevity of structures. Even without additional protective coatings (which should still be a matter of consideration), they perform significantly better as they do not trap moisture and contaminants, and are typically made of thicker steel, meaning that even when corrosion does occur, there are longer timeframes for a feasible repair.
Such measures no doubt add more to the initial capital expenditure. But with ongoing maintenance and repair costs in difficult to reach locations – both geographically and structurally – they create significant whole-of-life savings and improve amenity and safety.