Building / House Design

Lightweight or Heavyweight Walls

There are many ways to build a house and many different options to choose from. When it comes to a building’s structure, that being: the wall system that sits on the floor and holds up the roof, there are two main categories these systems generally fall into: lightweight / low mass walls and heavyweight / high mass walls.

Lightweight wall systems typically consist of timber or steel frames, which are then wrapped in a waterproof membrane and clad; alternatively, a brick façade can be built up, with a cavity between the bricks and waterproof membrane left to allow for airflow. In either case, lightweight frames are typically insulated between the studs due to their low thermal mass and poor sound insulating qualities.

A waterproof membrane on a house’s exterior wall

Despite these limitations, lightweight wall systems tend to be the most commonly used in residential building. This is because they are faster to install, use cheaper materials, and can also be pre-assembled offsite. While it is true lightweight walls have a low thermal mass, which restricts their ability to absorb and retain heat, quality insulation and passive design features, such as a polished concrete floor (which does absorb and contain heat) can prove to be more effective than a poorly devised heavyweight wall system. The lighter physical weight of these systems also means they can be used on most terrain, and in conjunction with most floor systems, as opposed to heavyweight
walls which require greater engineering and support systems.

Heavyweight wall systems include double-brick walls, concrete blocks, and pre-cast concrete panels. They have a high thermal mass and when designed properly are excellent at absorbing and storing the sun’s heat. This makes them useful for helping to passively heat / cool a home. Additionally, they provide effective sound barriers and, structurally, are able to bear heavy loads, which makes them useful for multi-story buildings.

A pre-cast concrete residence

Installation time for heavyweight wall systems can be slow, and either involve the need for scaffolding where bricks and blocks are concerned, or heavy machinery, such as a crane, to lift pre-cast panels into place. The engineering of such systems also requires additional attention and measures to ensure foundations are capable of bearing the heavy weight of the walls. On a sloping site, or in soft soil, this can result in significant earthworks.

Where other building systems are concerned, choices generally aren’t restricted by the use of wall system. Roofing options, for example, are fairly universal, and both lightweight and heavyweight walls can support roofing frames which are loaded with either concrete tiles or steel sheets. Both are also capable of supporting the additional weight of double-glazed windows and doors.

Double glazed doors on a brick veneer home

Where thermal mass is an important factor, heavyweight walls have a clear advantage in their ability to store solar energy, however, the overall design and positioning of a building can determine the effectiveness of a home to passively heat and cool itself. From a maintenance perspective, wall
cladding options for lightweight wall systems are easier to maintain and work with. It is easier to replace a damaged cladding board, for example, than a solid block; and it is easier to install post-construction service pipes, such as installing an air-conditioning unit, through insulation and cladding than it is to drill through concrete panels.

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