Metal roofs: 9 things you need to know

August 20, 2015

Sheet metal roofs are durable, attractive and relatively easy to maintain. Here are nine things you need to know about them.

  1. A metal roof is vulnerable to rust if the protective surface is compromised so don't let your tools scratch the sheet metal.
  2. If using more than one type of metal on the roof, put those that are more prone to oxidization (the less "noble" metals) above those that are less prone to oxidization (the more "noble" metals). The ideal order of metals (from the top down) is zinc, aluminium, iron and steel, lead, copper, then stainless steel.
  3. Your body weight can permanently dent or crimp the light-gauge metal used on most domestic roofs. When walking across a metal roof, follow the line of the fixings, where the roof has maximum support. Sheets with a high profile don't dent as easily as those with a low profile, but still follow the fixings.
  4. The sound of light rain falling on a metal roof can be delightful, but a deluge is deafening. When putting on a new roof, install a fibreglass or similar material insulation blanket underneath. It will deaden the sound, reduce condensation in the roof space and provide thermal insulation, too.
  5. When a roof corrodes to the point where holes start to appear, it's time to replace the whole thing. If you need a temporary solution, try filling the holes with sealant or covering them with pop-riveted patches – but make replacement a priority.
  6. Temperature changes cause sheet metal to expand and contract, resulting in creaks and groans. Aluminium and zinc expand twice as much as steel, so these tend to be the noisiest roofs.
  7. Constant expansion and contraction of the sheet metal in roofing can cause roofing screws and nails to work loose. Check regularly, and tighten loose screws and nails as soon as you spot them.
  8. Many sheet metal roofs are installed at a shallow angle, so there is always a danger that rainwater may flow back underneath because of surface tension. Turning down the edge of the sheets where they discharges into the gutter can reduce the likelihood of leaks in your roof space.
  9. The lead washers sometimes used under galvanised roofing screws may become cup-shaped over time, allowing water to flow underneath them and into the roof. To solve the problem, apply a dab of sealant to the undersides of affected washers. Alternatively, replace the washers.

Keep these nine things in mind when you're considering installing or working on a sheet metal roof, and you'll be better able to make it last.

Metal roofs: 9 things you need to know
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