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Over the last few years, I've learnt some expensive lessons regarding the maintenance of our galvanised metal roof. This post is mainly to my future self, to not make the same mistakes. I wish I could imbue readers with the experience I have learnt, but like so much of the work I do on Digital Transformations, using Agile and DevOps, you need to combine your own experience with some best practices to truly understand how to really make a difference. Like Verner Vogels says, "there is no compression algorithm for gaining experience".
Unlike a tiled roof, this is a fairly flat roof, made up of IBR sheets. I'm not quite sure why the original owner chose a galvanised roof over a tiled roof, because I dont see many galvanised roofs around in our area.
We have been living in this house for about 13 years, and we did practically no maintenance on it for the first 7 years or so. Perhaps because I was used to a tile roof, and a good painting every 5 years is all that you need. So for the last few years, we noticed an increased build up of rust.
We got some painters out, went to Builders Warehouse, and bought paint. And thats where the expensive lessons start. Depending on how you find at Builders that day, the may direct you to specific product. Some will say galvanised metal does not need priming, some will say it does. So will say use a rust cleaner, some wont, or wont tell you that it needs to be washed off thoroughly after application because its corrosive. So after many rounds and years of using inexperienced painters, with differing advice from the shops selling the paint, we sprung quite a big leak. The rust had eaten right through the metal sheeting, and water was getting to the ceilings.
I then got a professions company out to assess the damage, as well as the paint manufacturer. They found a number of problems:
- The waterproofing was applied far too lightly over the membrane mesh material on the joints.
- The roof paint was applied too lightly, probably only a single coat. You could see the streaks in the paint, exposing the metal underneath
- The paint was pealing, only a year after painting, which means it was not cleaned a primed enough
- We did'nt wash off the corrosive rust cleaners
- The tilt of the roof was not enough, meaning water will sit and not run off quickly enough
Basically, the mixture of inexperience (ourselves and the painters), differing and poor advice from stores, over the years had resulted in us just doing cover-up job over a bad foundation. Eventually, it was going to catch up to us.
We needed to replace the damaged sheets. When IBR sheets come out of the factory, it has an oil on it. You need to use a corrosive cleaner to remove this oil, wash it off, and then prime and paint. The advice we got is to let us naturally weather for 6 months, by which time the sun and rain will have removed the oily layer, then prime and paint.
Its actually really helpful to read the directions on the tin - alot of the guidance is there.
The best advice I received was from the paint manufacturer, who came out to inspect the roof:
- Use oil based primer - anti corrosive
- Do sanding and priming in a 4 hour cycle. If you leave themetail exposed for too long, corrosion set its. So on a particular section, sand for 3 hours, then prime for 1 hour (before 4 hours), then move onto the next section.
- dont paint in temps under 10 degress and above 35. Which means dont paint in the heart of summer and winter. And dont paint during the rainy season, as it will wash off your hard work, and expensive paint, and cause the paint to crack. So this time we painting in May, once the rain had stopped, but before the cold winter set in. But then the leaves are failing, and you end up painting leaves into your roof.
- On the joints, put a layer of waterproofing, apply the membrane, then another layer of waterproofing. Allow to dry for 24 hours, and then another coat of waterproofing. And then another. You should not be able to see the white texture of the membrane material, else you applied to little coats. Apply another coat for safety.
- Then 2 coats of roof paint.
- And every 6 months, slap on another coat of roof paint. The thicker the paint, the more layers the water has to work through to get through to the metal underneath. And each year, the sun and rain will reduce the layer of paint (cant remember how much he said), so even though the paint says its got a warranty of 5 years, rather be safe, and apply more frequently to protect your roof
I got this below from one of the quotes from a professional company, which validates why they so expensive, because they do it right from the start, and take all the guesswork out of it.