How to Pick the Right Metal Sheeting for Your Roof

by Tony Hobbs, Managing Director, Southern Sheeting

NOW THAT THE construction industry has returned to work, for many it will be time to think about choosing a metal roof for a building project.

Metal roofs can be a good investment because they are lightweight and durable. They are also very quick to install. Steel roofing sheets are extremely weatherproof, able to withstand high winds, rain, snow and even fire, so are an attractive option. An added bonus is that they are unaffected by fungus, moss, or mildew – and resistant to damage from wild animals and pests.

Today they come in a wide range of colour coatings and are an increasingly popular choice for builders and even DIY enthusiasts, having been used by professional roofers for many decades.

But even for the professional roofer, there are some key considerations when ordering materials from your supplier. Here are the key questions to ask before you place your order.

What are you using the building for?

Think about what you want to keep in the building. Do you need insulation, do you want to keep livestock inside and do you want to let light into the building? Will the goods stored inside be sensitive to condensation? In this case your roof may require an anti-condensation finish.

Condensation and metal roofs

Metal sheeting is a good option for a workshop or garage, but if there’s likely to be condensation you need to consider either an insulated sheet or anticondensation sheet.

A box profile anti-condensation sheet has an unwoven fabric applied to the underside which regulates condensation and stops it from dripping which works well for garages and animal housing. But in order for it to be effective the building must be adequately ventilated to allow the fleece to dry out properly. This is usually achieved by leaving the foam fillers out along the ridge and eaves.

Insulated panels made of steel will provide a warm roof but can be at least double the cost, however they are extremely effective.

Aluzinc Tr4 Tr5 Double Deck Roof Forming Machine

Another option which is a great fit for agricultural buildings, but often overlooked, is a built up system. These enable you to keep the old roof on, but use a liner insulation quilt or insulation board, followed by a steel top sheet. This reduces the costs of taking off the roof and reduces the cost of materials, however it will take more time to fit the roof.

Is your building coastal?

A coastal roof may require a more durable coating such as HPS.

Polyester or plastic-coated metal roofs?

Let’s take a look at the pros and cons of polyester or plastic-coated metal roofs. Polyester is of course a more cost-effective option. But it can be scratched more easily than plastic coated roofs, also known as plastisol. Polyester is only available in five different colours and has a life span of 15-20 years. Compare this to plastic coated and you will find a much more durable product, with a lifespan of 25 years and it’s available in even more colours.

There is also HPS to consider, which is a type of plastisol with an even longer lifespan, and also aluminium sheeting.

Corrugated or box metal roofs?

Metal sheeting comes in box or corrugated profiles which are sometimes referred to as Trapezoidal or Sinusoidal shapes. Corrugated of course is stronger because there is more metal and it has a nice aesthetic quality as it looks older. It works well with agricultural buildings. Think about your budget – box and corrugated are cheaper, aluminium is more expensive.

Tile effect or standing seam system?

There is also a steel tile effect sheet for roofing which is proving very popular in caravan parks. Or think about standing seam systems which look quite different and suit a low-pitched roof. We are seeing a growing trend for these on one-off houses. They cost more but the style has significant appeal.

What are the other roofing options?

Fibre cement, bitumen, polycarbonate, PVC, and insulated metal roofing are other options.

The skill level of the fitter is important to consider. Cement roofs require a high level of skill to install, for instance, so metal sheeting can be a better option for many.

Are there different qualities and prices when it comes to metal roofing?

Yes. Different thicknesses of sheet and different coatings are available depending on your budget.

What type of roof do you have?

There are many types but the most common is an apex roof (up and over) or mono pitch (single slope).

What are the measurements of the roof?

You will need to provide the length of the slope (including any overhang you want for your gutter). Then also think about the length of the building. If you also need sheeting for the rest of the building, not just the roof, then you will need measurements from the ground up to the eaves and the ground up to the apex. It is also useful to provide the angle of the roof, although this is not necessary for determining how many sheets are required.

What colour sheeting do you need?

The good news is that steel sheeting comes in up to 25 different standard colours, so there is plenty of choice.

Do you need lighting?

For buildings that need light you can include rooflights. These will match up exactly to any steel sheet but are translucent. How many you need depends on the type and size of the building, but between 10-20 per cent of the total roof area is a good rule of thumb.

Now that you have all these questions answered you are ready to begin!