I reckon the sarking is going to suffer from the heat of having nothing but building paper between it and the iron. quite apart from the lack of ventilation for water. And building paper isn't damp-proof course, it gets slightly damp if water, including condensation(which will happen) gets on it.
I'd only ever go rafters, sarking, purlins, mesh if it's not new self supporting paper, then paper, then the iron. I can hardly believe anything else is going to comply with the regs. not that I'm much of a stickler for regs, but I do like to know what I've done is going to work as it should and needs to.
nzshooter01,
Dec 25, 5:18am
I install fascia and gutter in chch, i see approx 200 or more new framed roofs per year, have never seen vented purlins, 45deg purlins or anything different to what i would have seen 30yrs ago, If any of this is being done its not in chch
nzshooter01,
Dec 25, 5:22am
If by mesh you mean netting i think that is only required for flatish iron roofs, say under 15deg or thereabouts
mechnificent,
Dec 25, 6:07am
True. The new paper is self supporting anyway I hear.
tweake,
Dec 25, 6:09am
how many of those roofs are sheathed? and with metal roofing
apollo11,
Dec 25, 6:31am
So if I were to think of re-roofing, could I remove everything back to the original purlins and then get the roofer to use those? Why would the roofer not have done this when they last re-roofed? Would there be some value in keeping the sarking in place?
tweake,
Dec 25, 6:39am
yes, it is structural. tho you could remove it and brace the roof in other ways. i've worked on places where they removed and sold the timber and that paid for the reno (or so i was told).
if you where doing a major reno on the place, i would leave it in place, and then put the ceiling insulation up under it and turn the ceiling space into conditioned space. makes for excellent storage and place to put ducted heat pump and ventilation pipes.
apollo11,
Dec 25, 6:50am
We have around 2 meters to apex, it's almost enough height to turn into a living space up there. I'd need to reinforce the ceiling/floor though, which starts to get expensive. Our sarking is only 10mm, so not something that you could do much with.
bergkamp,
Dec 25, 7:01am
no not structural in my case , the sarking has big gaps ,is hardly nailed and finishes roughly where the soffit starts - in other words no bracing potential. its there for condensation nothing else
thats not to say sarking in general is not structural
i would get a good builder to have a look - there are too many variables
does the area you are in have severe frosts?
apollo11,
Dec 25, 7:06am
Our sarking is only 10mm, nailed parallel to the rafters so won't be doing much for diagonal bracing or anything. We are inland, so we can get bad frosts. Why do you ask?
bergkamp,
Dec 25, 7:36am
as its an old house ,maybe ice was forming on the underside of the original roof , melting onto the ceiling . and the previous owner thought this was a solution
apollo11,
Dec 25, 8:19am
The house was originally from Upper Hutt- got driven over the Rimutakas to the Wairarapa. I've just remembered that in one spot I found a flashing with textured grit finish- like the decramastic tiles. It's possible that the newer purlins were set up for decramastic tile, and when re-roofed with coloursteel the roofer just used every second one of the purlins.
nzshooter01,
Dec 25, 6:35pm
75% long run iron,,25% metal tile Concrete tile dieded down here after the earthquake. By sheathed do you mean sarked with ply or similar? Only the bituminious shingle roofs, and yes im aware they are vented around the eaves, but those roofs are very few and far between . Interesting those shingles are sold as an expensive premiumn product in nz, in texas every house has them, cheap as chips
apollo11,
Dec 25, 8:01pm
Really? I didn't think they were a long lasting product. Slate shingles, yes- but not the bituminous stuff.
bergkamp,
Dec 25, 8:51pm
ok maybe this is what happened with your roof.
decramastic tiles require the paper to run under the purlin ,so maybe the roofer decided to utilize the sarking (maybe no self supporting paper at the time) and then set out his new purlins over the top - later the second roof became corrugate and used every second purlin
or decided to not use paper and only the sarking , after taking the old corrugate off he would have a clean slate to work with . otherwise he would have had to remove all purlins and all sarking (the correct thing to do )
apollo11,
Dec 25, 9:20pm
Yeah the more I think about it the more sense it makes. The roof is quite stiff between the purlins it is fixed to, so there are definately purlins under there. When I get the roof redone, I'll get the newer purlins removed, remove the old layer of building paper- but keep the sarking. I'll then get the roofer to add new purlins- perhaps 20mm treated ply strips- with screws into the purlins under the sarking.
bergkamp,
Dec 25, 10:41pm
not sure why you would need the 20mm strips? just rip the top roof off and go back to the original with new paper over sarking IMO
apollo11,
Dec 25, 10:45pm
To space the building paper and iron off the sarking, at least that is my understanding.
bergkamp,
Dec 25, 11:06pm
i dont know why you wouldn't put a breathable building paper directly on the sarking , its not a skillion roof and the sarking keeps the paper taut and straight .
tweake,
Dec 25, 11:14pm
sheathed with ply. really interesting to see very old houses had a similar sort of thing. kiwis don't sheath houses (very much) which is why you simply don't see it.
asphalt shingles. its really weird, one thing nz housing does right is steel roofing. usa shingles are dirt cheap disposable roofing. steel roofing is a premium product for long lasting roofs that don't get damaged in storms.
one of the houses i worked on many decades ago had asphalt shingles and i'm told it was all replaced within 10 years.
apollo11,
Dec 25, 11:23pm
I'm not a roofer, there must be a reason why they have the rules they do. I've been told that the building paper must be directly under the iron and that the iron and building paper must be spaced off the sarking. I don't know enough about it to challenge this.
tweake,
Dec 25, 11:36pm
the rules are minimums, you are allowed to do better.
the roofing underlay must be directly under the iron. but afaik there is no rule to say you cannot put house wrap on the sarking as well. you can have both. you just cannot have roofing underlaying on the sarking instead of under the iron.
house wrap to protect the sarking, roofing underlay to stop condensation dripping down.
the bigger problem is sheathing is so rare in nz most builders and roofers most likely have no idea what to do with it. most will only do what they do to every other roof and will not think past that. really need to get hold of guys who do high performance or passive houses. they will be well used to dealing with it.
apollo11,
Dec 26, 12:46am
Good stuff. I was thinking that it would be fine not to have a membrane on the sarking because it has decent gaps in it for air circulation.
There is already a layer of building paper directly on the sarking, it's super heavy duty stuff so might be quite old.
jacinda2059,
Dec 27, 6:47am
get an opinion from a good roofer, try Kenray roofing, in yellowpages, they will give you an honest opinion
fastspec,
Aug 30, 10:13pm
No pink dye as its easy to see where you've been and the pink dye gets on everything.
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