Exterior Cladding

New technologies and materials are changing how our homes look. Your choice of external cladding will of course govern how your home sits visually in the street or landscape, and so is clearly one of the biggest design decisions you’ll make. Investigate widely for cladding you like that fits with the style of home you’re building and with its setting, but don’t forget that durability is just as important as look and above all else, ensure your cladding is installed according to manufacturers’ instructions.

Traditional weatherboard has stood the test of time, but there are a huge number of alternatives available today, including new products that mimic the look but increase the durability, as well as entirely different classes of cladding.

Concrete block (plastered or natural), brick (also potentially plastered or ‘bagged’), plywood panelling, glass, rammed earth, and even fibreglass have all been used as ‘envelopes’ for homes. Waterproofing is critical, but problems of the recent past have largely been addressed and new homes today use specific techniques to avoid these issues.

Consider the following:

Ensure your choice of cladding will provide protection from the elements. If you’ve just moved to a new area, take into account the prevailing local climate and weather conditions, such as high wind and/or rain.
What is the insulation rating (R-value) of each system? Remember, the higher the R-value, the lower your power consumption and, generally, the better your family’s health will be.
Are the structural integrity and bracing values suitable for your site? Ensure the strength of your concrete is checked once it’s cured.
How rapidly will the cladding deteriorate? (Even weatherboards need replacing eventually.) Should water penetrate into the external walls, what internal materials will be placed at risk, and how does this affect the structural integrity of your home?
What about cost? Remember to balance cost of installation against ongoing savings you will make through trouble-free maintenance. Also consider the environmental impact, from manufacture through to the disposal of leftovers.
If in doubt, don’t be afraid to ask for the supporting information to reassure you that you have made the right choice.

Cladding options
Here are some of the main options for cladding a home.
Weatherboards are shaped planks ﬁxed horizontally and lapped over each other. Rainwater drains off naturally and can only get inside if it is forced upwards between the boards. There are new installation techniques that can greatly speed up application, keeping costs down.

As well as timber, weatherboards can be made from materials such as ﬁbre-cement (see below), metal and vinyl (PVC).
Fibre-cement exterior wall coverings come in the form of panels and weatherboards. They may be used as the exterior wall covering, or as substrate for monolithic claddings (see below). Fibre-cement sheets can also be plastered to give a monolithic effect.
Plywood panels are another traditional option; joins between boards are covered with battens or ﬂashings. Plywood weatherboards are also available.
Masonry veneer is a system where a timber-framed home is clad with bricks, stone, or thin concrete blocks. The masonry is connected to the timber framing through ﬂexible wall ties.
Concrete blocks or poured concrete may act as both the structure and the cladding.
Monolithic cladding systems have a seamless appearance. They have become popular in recent years, but need to be designed and applied properly or they can leak. The ‘leaky home’ problem is largely to do with incorrectly constructed monolithic cladding, but ongoing care is also essential: all monolithic claddings rely on the ﬁnal coat for waterprooﬁng, and this needs to be well maintained. The traditional monolithic system is stucco. Cement-based plaster is applied over a variety of backings, including ﬁbre-cement and plywood sheeting, and is then painted. This is the oldest of the three types of monolithic cladding and has been used in New Zealand since the 1920s.
Exterior insulation and finish systems (EIFS) are multi-layered, using polystyrene insulation and reinforced plaster or concrete. There are several different proprietary systems available.
Extruded aluminium panels or steel are highly durable, come in great-looking proﬁles, and are very low maintenance; they are coloured prior to delivery, so no painting is required.

Drained and vented wall cavities: some water will inevitably penetrate the outer skin of the building. A cavity between the outer wall covering and the interior lining allows water to drain away through holes and air to circulate in order to dry out. Building wrap and sometimes a plywood or synthetic barrier is installed under the battens to create and additional weather barrier. With most types of cladding, in all but low-risk situations a dry cavity is now required under the Building Code.

Wall underlays or building paper: Building paper and synthetic wraps prevent any moisture that does enter the wall cavity, or has got in behind the cladding, from penetrating the framing and interior lining.

Flashings: These are protective strips of metal or other material that cover joints and gaps where water might otherwise get in. They are used around window frames, external doorways, and on top of exposed walls, to help stop water getting in, and also to help drain it out.

Cladding tips
Remember that you can introduce more than one system into your architectural designs, but ensure they will work together. In particular, watch out for the following:

Is the cladding handled and installed as per manufacturer’s instructions, and are there no damaged panels?
Have the flashings been affixed correctly and properly waterproofed?
If using flat panels, are the joins between panels even and regular, and is there sufficient protection from the rain?
Are battens used to aid in drainage for water that gets behind the cladding?
Is the cladding finished properly and does the job look neat?
If using more than one cladding system or material, does anyone on your project – your designer, your builder or your project manager – know how the different materials will react when placed against each other?
Has the builder used copious amounts of silicone to waterproof gaps? If this is the case, fire them.