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| Thread ID: 48136 | 2004-08-15 03:56:00 | Off Topic -Difference between galvanised iron & steel roofing? | Laura (43) | Press F1 |
| Post ID | Timestamp | Content | User | ||
| 261846 | 2004-08-15 07:32:00 | Mike, your correct, both products I referred to use Zincalume rather than galvanising as the base corrosion resistant coating. Having said that, I'm not that sure whether it would be better than the old fashioned, thicker, method of galvanising that was the norm way back when. Cheers Murray P |
Murray P (44) | ||
| 261847 | 2004-08-15 07:34:00 | Years ago corrugated iron was imported and often travelled as deck cargo. If you have ever seen a roof where all the edges were rusting but the rest was alright that was why. If you live by the sea the warranty for coloursteel is not as long as for inland. Often you can leave uncoated corrugated iron for quite a time before painting. Almost as long as the warranty for colour steel. This can help reduce the initial cost of reroofing. I was water blasting a roof back in Feb at 3000 psi. After doing so I suggested it was a waste of time painting it as I blew holes in it in parts. |
mikebartnz (21) | ||
| 261848 | 2004-08-15 07:56:00 | Galvanised roofs were (are) left to weather to get rid of the lubricating oils from the roll forming process, more effective than etching or other cleaning methods IMO. A few months usually does the trick, then the paint will stick. Most roofs rust at the laps because the laps have not been primed before installation or because of capillary action holding water in the laps for long periods of time along with buid up of salts where natural washing cannot remove them (same under nail heads) or, a combination of the preceding. Salt may have come from transport but I would have thought that roll forming would have removed it (very early corrugated was most likely to have been roll formed before arrival). Cheers Murray P |
Murray P (44) | ||
| 261849 | 2004-08-15 08:13:00 | The deck cargo I was talking about was the final product. A little bit of plumbers spirits of salts in water ( about a desert spoon or less in 10 litres) is great for washing a new roof off to get rid of the oils. I have seen a lot of builders prime the edges but they have not removed the oils so the paint does not adhere properly which in my opinion is worse than leaving the edges unpainted initially. |
mikebartnz (21) | ||
| 261850 | 2004-08-15 11:17:00 | Fascinating. I've certainly learned something today. There are quite a few examples of 100 year old unpainted corrugated iron in Central Otago, still doing the job. Remarkable. I'd guess your roof is newer in Dunedin, Laura. Wetter and more salt in the air. Good luck. |
Winston001 (3612) | ||
| 261851 | 2004-08-15 11:44:00 | >idiots using pencil to mark, That has me curious have probably been guilty of that myself. :8} What does the lead in a pencil do to the galvanizing. I have never heard of that being a no no. Those niblers are a great little invention but I have been on a number of roofs where they have not cleaned the swarf off. Was on a new Wharehouse roof recently and there certainly did not feel like there was much between me and the floor about ten meters below. |
mikebartnz (21) | ||
| 261852 | 2004-08-15 12:05:00 | Laura, our roof had a few sections of old galv-corrugated steel that had rust holes and spots, and I am sure a roofer would have said to replace with new. But I simply removed the loose bits and applied a rust kill (turns iron oxide into a blue-black different material), then patched the holes with a trimmed venetian blind (aluminium) and stuck them on with silicon cement. Then I painted the patched areas with a rust kill paint. Finally I applied 4 layers of roof paint. That was 4 years ago and no rust has come through. By the way, the venetian blind slats are curved and are a good fit on the corregated iron. On the other hand, older homes like your's and mine have small sections of corregated iron (not the modern long lengths). It is really easy to pull up the rusted small sections and hammer in a new one..... and much cheaper to do it yourself. |
Steve_L (763) | ||
| 261853 | 2004-08-15 23:27:00 | > What does the lead in a pencil do to the galvanizing I'll retract the idiot's comment then ;) Carbon black in black rubber (for washers and flashings) and pencils etches the surface of galvanised, zincalume and colour steel materials which will promote corrosion, besides being hard to get off. Any colour pencil other than black is ok, neoprene or silicon rubeer is ok. Cheers Murray P |
Murray P (44) | ||
| 261854 | 2004-08-16 00:08:00 | Thanks once again to all you helpful gents. Lots of options there, plus enough background info to keep us from falling into some of the roofing traps. And as we've all got some kind of roof, maybe Winston wasn't the only other PF1er to find it fascinating... (Today, of course my roof looks simply dazzling - glorious in its pristine white. What a pity I can't keep the snow glued on there, once it has melted everywhere else...) |
Laura (43) | ||
| 261855 | 2004-08-16 03:25:00 | Final note: "gauges" as in 24 gauge, 26 gauge, etc, are non-intuitive. Bigger numbers mean thinner. With thickness as in 0.4mm, 0.6mm, etc, bigger numbers mean thicker. | Graham L (2) | ||
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