Hughes
Hughes - Extension Project in Blairgowrie
The Hughes Blairgowrie extension blends energy efficiency, flexible timber sub-floors, and Class S soil considerations for a sustainable, adaptable home upgrade.
House extensions have become increasingly popular in Australia, as they cater to the evolving needs of homeowners. Here, we’ll highlight the features of our Blairgowrie project, highlighting its class S soil, timber sub-floor, and the energy efficiency enhancements of both the extension and the existing property.
Soil Classification
In Australia, soil classification is primarily based on the reactivity of the soil, which relates to how changes in moisture content can affect building structures. This classification is crucial for construction and civil engineering because different soil types perform variably under the load of a building(see figure 1). Here’s how it impacts:
Foundation
Class A - Most sand and rock sites with little or no ground movement from moisture changes
Class - S Slightly reactive clay sites with only slight ground movement from moisture changes
Class - M Moderately reactive clay or silt sites which can experience moderate ground movement from moisture changes
Class - H Highly reactive clay sites which can experience high ground movement from moisture changes
Class - E Extremely reactive clay sites which can experience extreme ground movement from moisture changes
Class - A to P Filled sites — see AS 2870
Class - P Sites which include soft soils, such as soft clay or silt or loose sands; landslip; mine subsidence; collapsing soils; soils subject to erosion; reactive sites subject to abnormal moisture conditions or sites which cannot be classified otherwise
Table 1: General Definition of site classes
Source: NCC
Foundation Design: Soil types determine the required load-bearing capacity and waterproofing needs.
Drainage Systems: The soil’s drainage ability influences moisture management around the foundation, possibly necessitating specialised drainage solutions.
1Site means the part of the allotment of land on which a building stands or is to be erected.
Building Material Selection: Certain soils may require specific building materials to accommodate their chemical properties, such as corrosion-resistant materials for high-salinity soils.
Long-term Maintenance: The stability and variability of the soil also affect the long-term maintenance needs of a building, possibly requiring regular inspections and reinforcements.
According to Mornington Peninsula Shire, the predominant soil types in the area are sandy soil, brown loam soils, and deep volcanic soils, most of which range from Class A to Class S in reactivity. In our Blairgowrie project, Class S soils are particularly significant due to their slight reactivity to moisture changes. In environments like Mornington Peninsula, where the climate tends to be humid and moisture levels are relatively high, managing these slight changes is crucial. Proper assessment and construction methods tailored to these soil conditions help ensure the structural safety and longevity of buildings.
Timber Sub-Floor V.S. Concrete Slab: Which to choose?
Choosing between a timber sub-floor and a concrete slab can significantly impact the cost of your project. Factors such as finished heights and design flexibility can greatly influence your choice from a cost perspective. Here’s a detailed comparison:
Finished Heights:
Timber sub-floors allow for more flexible adjustments to finished heights, which is particularly advantageous in uneven terrains or buildings requiring specific floor heights. For instance, on sloped terrains, timber sub-floors can adapt to the landscape by adjusting the height of the supports, a process that would significantly increase costs with concrete slabs.
Meanwhile, adjusting the height of a concrete slab is difficult and costly, as it often requires additional excavation or soil filling to achieve the desired height. While concrete slabs provide stability for buildings that need a flat, robust surface, like industrial warehouses, the cost of adjusting their height can be higher.
Design Flexibility:
Timber sub-floors offer greater design flexibility. They allow architects and designers to easily modify or upgrade utilities such as piping and wiring throughout the building’s lifespan, typically by removing the timber board overlay to reveal the subflooring underneath. This flexibility can lead to lower initial costs and potential long-term savings due to ease of maintenance and upgrades.
On the other hand, due to their robust structure, concrete slabs are better suited for designs that need to support heavy loads, such as large machinery or frequent vehicle movement. Although the initial construction cost of concrete slabs is higher, they may provide better long-term value in scenarios requiring high stability and durability.
In our Blairgowrie project, we opted for a timber sub-floor due to its height, adaptability, and various other factors we considered. Contact us today to let our experts help you choose the right options for your home extension.
Energy Efficiency Requirements:
In recent years, Australia has implemented more stringent regulations on energy efficiency within the residential construction sector. These regulations aim to significantly reduce energy consumption and greenhouse gas emissions, aligning with broader environmental goals. The enhancements to the energy standards are structured around three main areas:
Energy Efficiency Ratings: In Australia, the Nationwide House Energy Rating Scheme (NatHERS) provides an energy rating of up to 10 stars, taking into account the home’s design and construction materials such as walls, insulation, windows, and roofs. With the latest updates to the National Construction Code (NCC), the minimum star rating for new homes will increase from 6 to 7 stars. This means that all new homes must meet higher standards in design and materials to achieve improved energy efficiency and environmental performance, thereby advancing residential construction towards greater energy conservation and emission reduction.
Whole-of-Home Ratings: Alongside the NatHERS star rating, a new Whole-of-Home rating system has been introduced, providing a second metric that evaluates a home on a scale up to 100. This new rating system not only assesses the building’s structural energy efficiency but also includes the energy performance of appliances used for heating, cooling, and hot water. The introduction of this rating encourages residential builders and designers to consider the efficiency of the appliances they recommend to their clients, promoting a more comprehensive approach to energy conservation in home design.
Specific Building Components: The NCC emphasises the use of higher R-value insulation in walls, ceilings, and floors to enhance thermal efficiency. This includes specifications for internal wall insulation, particularly in unconditioned spaces like laundries and bathrooms, as well as increased requirements for slab and underslab insulation.
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