What follows is a short crash course on how to install metal roofing of any sort. No matter what type of metal roofing, be it copper, zinc or steel, it could be roll formed sheets or standing seams, it could be external screw fixed or have hidden clips, basic good construction practices apply to all of them.
Before you start to install the metal roofing
Think ahead. Do some research, there are new improved materials and methods appearing all the time. Prepare well and the hard physical work actually on the roof will be a lot easier and you will rest easy at night knowing the satisfaction of a "job well done".
If you have not fixed the product before make doubly sure that you know the correct procedure and fixings. Get the manufacturer's data sheets and comply with them. Make yourself aware of galvanic corrosion and how to prevent it happening in the particular metal roofing that you are installing.
Make sure that you have the correct vapor barrier, sarking, underlay and insulation materials.
One thing that you do not want to do is to get all your material up on the roof and then find out that it is wrong size, check it first.
You do not want to be ready to start work only to find that you have not got a specific tool on site.
A few years ago a friend of mine was selling his three quarters of a million dollar home when the deal came to an abrupt halt. The purchaser's inspection had found that the roof was incorrectly fixed. The people that had fixed the roof originally had used the wrong screws. They must have done it in ignorance, no one would have done it on purpose, but probably some salesperson had told them they were OK.
Before I get down to the nitty gritty of how to install metal roofing, a few words of caution. All work on a roof has the potential to be dangerous, and unfortunately accidents do happen, so please don't ignore safety.
Check your local regulations regarding safety and comply with them.
Walk around the whole building and make absolutely sure that you know the position of any electrical services. The main point of entry for power, any other power lines in the vicinity. All metal roofing products are great conductors of electricity. You do NOT want to be handling sheets close to live electrical wires.
Secure the access to the roof, if it is a ladder make sure that it is long enough to set three rungs above the roof.
Use and electrical safety box. Known as ELD (earth leakage detector) or RCD (residual current detector). Dragging power leads across sharp metal edges should not be done, we all know that, but hey, accidents happen, so use a safety box.
The steeper the roof the greater the danger. Make safety provisions for steeper roofs.
Do not allow anyone on the roof who does not have to be there, who has not got a basic grasp of roofing safety.
Watch out for dampness, dew or condensation. This can cause slipping.
Never work on a metal roof in rain.
Do some preliminary checks
Do a few checks before you order your materials or start to install metal roofing.
You may or may not be the person who did the roof framing or fixed the roof trusses, but it never does any harm to double check on previous work. You want to know if the roof framing is slightly out of square, or if it is not parallel. None of these things are easily seen so run your tape measure over the roof to check things out.
The old saying of "forewarned is forearmed" comes to mind.
I use a 30 M. (say 100 ft)long fiberglass tape measure and I like to use it when doing these early checks. I can slip the end over a nail and know that it won't fall off before I can get the measurement. This way it is a one man job.
Check the roof for square.
On a gable roof just check that the diagonals are equal.
If it is a small amount out of square then because you are aware of the fact, when you install the metal roofing sheets you can induce a small amount of creep into each sheet to correct the problem.
On hip roof this is not as important as the roof sheeting that touches the hips has to be cut anyway.
Check that the fascias are parallel to the ridge. Again this is not a big deal as small differences can be lost at the ridge when the ridge capping goes on.
Installing the metal roofing
The first sheet on each roof surface is the most important one. Get that one right and it will be plain sailing. Get it wrong and the job will be difficult from the start.
Determine the overhang at the fascia. With our local metal gutters I may let the sheets overhang say 60mm.
If there is definitely to be no gutters fixed then I may go with a longer overhang.
Fix a string line set off from the fascia the amount of the required overhang plus 2mm for clearance.
Tack the first sheet temporarily in position and check it for being square with the fascia.
On a roof with hips the first sheet fixed will be the first full length one at the hip.
Make sure that this first sheet is absolutely square off the fascia. Do not just rely on eye balling the end of it against the string line. That is not accurate enough.
The very best way to make sure it is square is to do a 3:4:5 measurement.
Tack or hold the sheet at the bottom with the top of the sheet able to be moved.
Using metric sizes, measure 3M. up the sheet from the face of the fascia and put a mark.
Measure along the fascia 4m and put another mark.
Measure the diagonal between the marks, it should be 5M. If it is not, then swing the top of the sheet until the diagonal is exactly 5M.
You have now got the long side of this first sheet exactly at 90 degrees to the fascia.
Fix the sheet and then continue placing the others in position, checking that they are OK with the string line and fixing them.
When walking on the roofing material always try step on the roofing where the under laying supports are. The purlins or battens.
This is particularly important on flatter roofs. It can be easy to dimple the metal by being careless and stepping in between supports.
At the end of work every day clean down the roof. All drill swarf and scraps should be removed.
So, to sum up, do your research, make sure that you have the right materials and the correct fixings.
Then once on the job look to safety first. Do your preliminary checks to make sure there are no hidden traps that you should be aware of. Then start installing the metal roofing with confidence. Clean up and rest easy.
Bill Bradley is a retired builder-general contractor with 50 years experience in the home building industry. Bill has written more about how to install metal roofing on his own website that he has built to help home owners and the DIY.