Roof basics – Metal roofs

Above is a roof to a deck that we did a couple of years ago. There is a large 25 deg. square hip roof at the rear, with steel hips and tie beams, and with timber rafters and purlins. In the front are all steel sloping roofs with angle iron rafter beams and RHS steel purlins.

all steel hip roof over deck or pergola

Roof basics – All steel pergola roof

Here is an all steel roof that I built in my back yard about 10 years ago. The thing on the top is a rotary roof ventilator, with a 600 mm diameter opening. They are not normally so big, 300mm is normal. The side facing is about 7m wide and the one leading away is about 8.5m.

inside of an all steel roof showing hip beams, tie beams and steel purlins

Roof basics – All steel pergola roof.

Here is a shot of the inside of it. As you can see, I have not got around to lining the inside of it yet. (So much to do so little time). Anyway at least you can see the structure. The perimeter fascia purlins are C25025 I think from memory, The next up is a 150×100 RHS tie beam then the rest of the purlins are C150s. I go into a bit of detail about setting out roofs like this on my roof calculations page, with rafter top cut, jack rafter side cut, hip and purlin side cuts.

Apart from the fact that steel can be curved, welded at odd angles and create unusual designs, steel has a couple of other advantages over timber.

It is easier to comply with fireproofing regulations.

I live in an area that has significant termite problems, and so strict regulations regarding termite control are in place. In some instances, these regulations. may be waived if all steel is used.

It can span greater distances cheaper than other materials. (I used to work for a timber engineering company that made huge laminated trusses and beams, so I know it can be done with timber, but I am talking about home building or extending here).

steel metal roofing

Roof basics – An all steel roof.

An ability to work with steel is required, but an owner builder can do a lot of work himself and hire a tradesman welder for the technical bits. If you can use a grinder and a chop saw, a hammer and a spanner, go for it!

Click here for some more on, steel and tropical roof design,

Roof Cladding / Coverings

Here is a list of roof coverings that I have had experience with, along with some (biased) comments. There are many others, like sheet metal products like lead, copper, stainless steel and zinc. Some with the modern standing seam jointing methods. To be honest I have never worked these, so I will confine my comments to the ones that I have first-hand experience of.

Hardies “super six” corrugated FAC, Fibrous Asbestos Cement, the infamous “Fibro”. If you still have a roof with this on it, I will say get rid of it. If you have to go on a roof like this, be extremely careful walking on it, especially when it is wet, as it is prone to deterioration with age and it is easy put a leg through or worse. Been there, done that! More on my asbestos page.

fibrous asbestos cement FAC roof

Roof basics – Asbestos roof

Slate. As an apprentice I have fixed broken or leaky roofing slates, but I can hardly remember the technique. One abiding memory is of starting to slide down a 45 deg slate roof, three floors up, and running madly sideways, gaining enough distance to leap 12ft onto a flat roof one floor below. No more slate roofs for me, thanks.

Concrete / cement roof tiles. Monier. Min roof pitch 15 deg but steeper is better.

The company that supplies the tiles also fixes them.

An excellent roof, if everyone who works on the roof later does the right thing, they will never give any trouble.

Unfortunately, plumbers, electricians and antennae installers tend to crack tiles.

I have found that replacing tiles is not that easy when the tiles are fixed with cyclonic clips. Replacing the ones that are just nailed is simple enough.

I usually try to fix any cracks with “Liquid Nails”, not silicone.

Our first house had Monier tiles, and I found it hotter than other houses. The concrete soaks up the heat during the day and keeps it well into the night. The company has a line of light-coloured tiles, white etc. that are better in this respect, but somehow white tiles look odd to me. When I think tiles, I think Terracotta.

decramastic metal tile roofing