Standing Tall: Choosing Materials For A Flat Roof Skylight Upstand
When choosing a new flat roof skylight for your home or place of business, it's common to spend hours debating which materials to use for the glazing and framing of your skylight while completely forgetting about the upstand. However, a well-made upstand constructed of suitable materials is a vital component of any flat roof skylight, and choosing a good material for your upstand can ensure many years of efficient, leak-free service.
What is an upstand?
The upstand of a flat roof skylight is the raised frame that prevents the skylight from lying flush with the rooftop. This prevents the accumulation of rainwater that can cause mould and corrosion and also ensures a tight, watertight fit around the frame of you skylight, especially if the existing roofing membrane is integrated into the upstand. Many upstands are tilted to further aid rainwater drainage.
Which materials are suitable for upstands?
Ideally, your skylight's upstand should be made of a material that is waterproof, weather resistant and not prone to rust or corrosion. An upstand should also be made of a material with good heat insulating properties, as this will greatly affect the amount of heat exchange that occurs through your skylight, lowering heating bills in winter and air conditioning bills in summer. The following three materials are most commonly used for upstand manufacture, and have their own particular strengths and weaknesses.
uPVC: This durable plastic is commonly seen framing windows on new residential builds and has a number of properties suited to upstand building; it is waterproof, durable, and treated to resist the damaging effects of intense sunlight, a positive boon in any Australian summer. uPVC also has reasonable heat insulation properties, and many uPVC upstands are manufactured with an internal layer of insulating foam to supplement this effect. However, uPVC is not invulnerable, and since it is so difficult to repair in-place, a damaged uPVC upstand often necessitates a full skylight replacement.
Timber: Timber is often used to create upstands for the excellent amount of heat insulation it provides. Its versatility and easiness to work means it can be used to create almost any shape and angle of upstand, and with the right surface treatments, a timber upstand can endure many years of weather and sunlight damage. Timber upstands are also more aesthetically versatile than other upstand materials and will complement the appearance of practically any home or commercial building. Bear in mind that some woods are far more suitable for upstand manufacture than others -- choose an upstand made from a durable hardwood, preferable a tropical or native Australian variety as these tend to have excellent weather resistance.
Aluminium: Often seen integrated into skylights in larger commercial and industrial buildings, aluminium upstands are the last word in sheer durability, and will take an inordinate amount of punishment before failing. Aluminium does not rust, and can be coloured with a variety of weather-resistant paints to achieve the look you desire. However, they have very poor heat insulation properties, and if the slow buildup of natural oxidisation on the aluminium's surface is not occasionally removed, the upstand may lose its watertight seal and cause leaking.