In late 50s my father built a shed at home with a malthoid? roof. Apparently it needed a tar coating covered in coarse sand as a protection from the sun. In the 80s he hadn't done that for awhile and it started cracking. Fixed with layer of corrugated.
apollo11,
Jan 5, 8:46pm
A mate made the mistake of using onduline. What garbage that stuff was.
bergkamp,
Dec 24, 5:01am
Just wondering if anyone has a product they could recommend. I am reroofing and would like to spray native timber sarking and purloins with metelex just for future proofing, the problem is the metelex is turps based and needs to evaporate for a week or so otherwise it could melt the roofing paper.
mechnificent,
Dec 24, 5:30am
There's a product called everdure, made by epiglass. but it's expensive as hell and overkill. It's two pot and soaks right in and hardens soft or rotten wood good enough to glue or screw. and kills and prevents moulds. but as I said, it soaks in, like crazy. it would take heaps. Good for boat building though or repairing small bits.
Won't the sarking have purlins over it ? That will hold the paper off the sarking. But metelex smells huh. for a long time.
apollo11,
Dec 24, 6:06am
Perhaps something water based?
bergkamp,
Dec 24, 6:10am
yeah i was thinking about "timbor" water based and safe , but i dont think you can get it retail very easily
bergkamp,
Dec 24, 6:11am
sarking sitting atop the purloins , but terminate at soffit line
mechnificent,
Dec 24, 6:13am
But doesn't that mean the sarking is right against the iron. Where's the air gap or insulation go ?
mechnificent,
Dec 24, 6:17am
How about treat the sarking first, before it's put up "
bergkamp,
Dec 24, 6:29am
the sarking is right up agst the iron , its basically what they used back in the day , there is plenty of air movement as its not a skillion roof
fastspec,
Dec 24, 6:29am
Framesaver
bergkamp,
Dec 24, 6:29am
its a reroof , so i will be taking 4 or 5 sheets of , laying vertical building paper and then immediately reroofing
fastspec,
Dec 24, 6:33am
Usually the purlin is much thicker than the sarking at the eave so there is a gap between sarking and iron. Look at the synthetic papers, there is one that is black on one side and white on the other, self supporting that is very good.
bergkamp,
Dec 24, 6:41am
after ringing thermakraft - as i understand it , both kraft based and synthetic papers require evaporation
bergkamp,
Dec 24, 6:41am
this looks good , similar to timbor i think . thanks
fastspec,
Dec 24, 6:57am
I've used a lot of it, its got a lot of glycol in it which helps the borate penetrate the wood- yes very similar to Timbor but intended to deal with rot as well as borers- essentially borax and boric acid in a glycol carrier. Get the one without pink dye in it.
bergkamp,
Dec 24, 7:13am
why no dye ?
the other bugbear about metelex is it corrodes galv fixings ,albeit in wet enviroments and probably only mimimally as it is an envelope preservative- this stuff doesant
apollo11,
Dec 24, 7:15am
We have the original purlins, then 10mm rimu sarking, and at some stage someone has reroofed and added another layer of purlins on top. The end result is that the iron sits high above the barge boards and lets wind driven rain into the eaves.
tweake,
Dec 24, 8:25am
ideally have membrane on top of the sarking. the purlins on top want to be at 45 degree for drainage rather than the normal horizontal. (tho you can get plastic(?) purlins which have drainage holes through them and fit them as per normal) roofing underlay on top of that then iron. fit proper sized barge boards/eaves etc.
its the "modern" way of doing it.
apollo11,
Dec 24, 8:51am
I'm not sure why it was done, unless it was for air circulation between the iron and the sarking? There is underlay directly on the sarking (under the newer purlins) and another layer on top of the newer purlins. I've had to screw a strip of galv steel to the top of the barge boards around the entire house.
bergkamp,
Dec 24, 9:10am
very odd , are both purlins set out the same ?
bergkamp,
Dec 24, 9:11am
i think he is talking about an original structure ,not a new build
apollo11,
Dec 24, 9:16am
Sorry bergkamp, I didn't mean to co-opt your thread. The original purlins are slightly closer together in spacing than the newer ones. It worries me a bit because the newer purlins are basically just nailed to the 10mm sarking in a lot of areas.
bergkamp,
Dec 24, 9:41am
you have purlins hanging on by a thread then ? it doesant make much sense -do you have easy access in the roof space, what pitch is the roof? any chance of getting some kind of direct connection between the rafter and outerpurlin?
i'm putting in blue purlin screws as an extra , through the sarkin g/purlin/rafter
apollo11,
Dec 24, 9:52am
The top purlins are spaced off the rafters by the original set of purlins. I'd need to use some sort of steel bracket to bridge the gap. I'm tempted to get the roof redone and rip off the top purlins and sarking, but I don't know if that would compromise the roof in some way.
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