Browse Forums Heating, Cooling & Insulation Re: Is sarking necessary with Colorbond roof? 2Sep 16, 2008 2:07 pm Hi Dale,
If you look at page 14 of my thread there is some info on what I have found out about sarking (thanks to Clarity who pointed out I didn't have any!): https://forum.homeone.com.au/viewtopic.p ... &start=195 If I'd found out earlier I probably would have got it, but I'm not too worried as I believe it isn't a legal requirement. Hope that helps Re: Is sarking necessary with Colorbond roof? 4Sep 16, 2008 4:58 pm It is required under the building code. Re: Is sarking necessary with Colorbond roof? 5Sep 16, 2008 11:07 pm Dukekamaya It is required under the building code. Which building code? Is it a national or a state thing? Funny that both my builder and Kevin don't know about this - I would have thought that if sarking was required, builders would have to offer it as standard, not as an optional extra? Re: Is sarking necessary with Colorbond roof? 6Sep 17, 2008 8:01 pm QUOTE from Colorbond site:
"Condensation forms under/on roof sheeting when the sheeting becomes colder than the air in contact with it. Water vapour carried in the air then condenses on the colder surface of the roof sheet. To minimise the risk of water damage to ceilings or corrosion related to condensation under steel roof sheeting, a vapour barrier should be provided under the sheeting to prevent contact between the moist air in the building and the roof sheeting." Re: Is sarking necessary with Colorbond roof? 8Sep 17, 2008 10:09 pm It says the same thing in the building code (BCA - Building Code of Australia) - I checked.
Perhaps its not as much an issue in Victoria. It would be unheard of to not use it under metal in NSW. My old metal roof did not have sarking under it ( kit home by cheap no-frills company) and I was amazed at the damage it caused. Some of the battens were literally split in half (longways) due to the effect of moisture/ heat directly on them. Having spent time in my roof both old and new, the difference is incredible between sarked and non-sarked. Re: Is sarking necessary with Colorbond roof? 9Sep 17, 2008 11:26 pm Our previous house had colorbond/no sarking but was steel framed...our independent building surveyor gave the same advice as what Kevin did...
donuts Sarking is applied for 2 reasons: 1) to stop condensation - in his opinion a lot of sarking is not installed properly and does not effectively stop condensation anyway, so he is not worried that we don't have it for this reason 2) to reflect heat in the roof cavity - and a whirly bird will do the same thing as this so we might just get one of those installed after handover. Donuts are your battens steel or timber? mmm....donuts Homer Simpson 1956- Links: Site Costs Ready Reckoner | H1 Addiction Medical Advice | Château TDL: The Backyard Re: Is sarking necessary with Colorbond roof? 10Sep 17, 2008 11:32 pm to_do_list Our previous house had colorbond/no sarking but was steel framed...our independent building surveyor gave the same advice as what Kevin did... donuts Sarking is applied for 2 reasons: 1) to stop condensation - in his opinion a lot of sarking is not installed properly and does not effectively stop condensation anyway, so he is not worried that we don't have it for this reason 2) to reflect heat in the roof cavity - and a whirly bird will do the same thing as this so we might just get one of those installed after handover. Donuts are your battens steel or timber? You're also forgetting about embers from the bushfire that could sweep through Highpoint! Seriously though.. that's another consideration in bushfire areas. I leave you to fend for yourself, figure things out yourself. Terrence Malick Re: Is sarking necessary with Colorbond roof? 12Sep 18, 2008 8:27 am Our builder friend advised us to have sarking since we are having a colorbond roof and now I guess I'm wishing we'd followed his suggestion. We should have asked him why then we'd have understood. Sounds like it's something worth putting in. Re: Is sarking necessary with Colorbond roof? 13Sep 18, 2008 5:46 pm I've been doing some research on this sarking thing and it's a bit bleeding confusing....yet another building thing made hard...I even looked on another forum....
This is what I found on the BlueScope steel site (they make steel roof sheeting) Condensation forms under/on roof sheeting when the sheeting becomes colder than the air in contact with it. Water vapour carried in the air then condenses on the colder surface of the roof sheet. To minimise the risk of water damage to ceilings or corrosion related to condensation under steel roof sheeting, a vapour barrier should be provided under the sheeting to prevent contact between the moist air in the building and the roof sheeting. Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ Reflective foil laminates (sarking) which are commonly used to provide heat insulation under roof sheeting can serve a dual function as a vapour barrier, by thoroughly sealing the foil overlaps with moisture impervious adhesive tape. The laps should be about 100 mm and kept in close contact when positioning the laminate so the tape can be readily applied. The laminate must be allowed to drape between the roof supports so that the cold temperature of the roof sheeting will not be transmitted to the laminate by contact. If this were to happen condensation could form on the underside of the laminate and may drip into the ceiling space. Ventilation of the ceiling cavity may assist in the reduction of condensation however it has been shown that ventilation will not completely eliminate the condensation cycle. In certain marine situations ventilation may also carry salts into the roof cavity which will, in the presence of condensation, lead to accelerated corrosion attack. What I picked up from this....and the other forum.....is that if the sarking is not installed properly, that is, not draped properly then sarking (from the point of view of preventing condensation is next to useless)...and I think this is Kevin's point. Also if the sarking is in direct contact with the colorbond then it's no good as an insulator as the colorbond will transfer heat directly to the sarking and then into your roof space. So therefore I think the message is if the sarking is installed properly...it forms an effective moisture barrier and thermal barrier (and bushfire, draft, and rain barrier), but if it is installed tight as a drum it's next to useless.... I don't think I'm helping.... mmm....donuts Homer Simpson 1956- Links: Site Costs Ready Reckoner | H1 Addiction Medical Advice | Château TDL: The Backyard Re: Is sarking necessary with Colorbond roof? 14Sep 18, 2008 5:52 pm Mike.... nerds are supposed to use their powers for good not evil .... this is bloody confusing isn't it?
We will have sarking... now I'm all I leave you to fend for yourself, figure things out yourself. Terrence Malick Re: Is sarking necessary with Colorbond roof? 15Sep 18, 2008 5:53 pm Sorry..... ....I have failed all nerdom! mmm....donuts Homer Simpson 1956- Links: Site Costs Ready Reckoner | H1 Addiction Medical Advice | Château TDL: The Backyard Re: Is sarking necessary with Colorbond roof? 16Sep 18, 2008 5:54 pm to_do_list Sorry..... ....I have failed all nerdom! You failed nerdom when you took up running! Nerds don't run! I leave you to fend for yourself, figure things out yourself. Terrence Malick Re: Is sarking necessary with Colorbond roof? 17Sep 18, 2008 5:57 pm joles to_do_list Sorry..... ....I have failed all nerdom! You failed nerdom when you took up running! Nerds don't run! Great....I'm a try hard-Nerd.... ....is there anything more pathetic.... mmm....donuts Homer Simpson 1956- Links: Site Costs Ready Reckoner | H1 Addiction Medical Advice | Château TDL: The Backyard Re: Is sarking necessary with Colorbond roof? 18Sep 18, 2008 5:59 pm to_do_list joles to_do_list Sorry..... ....I have failed all nerdom! You failed nerdom when you took up running! Nerds don't run! Great....I'm a try hard-Nerd.... ....is there anything more pathetic.... Actually I don't think there is.... You're even too uncool for Nerdom! I leave you to fend for yourself, figure things out yourself. Terrence Malick Re: Is sarking necessary with Colorbond roof? 19Sep 18, 2008 7:40 pm Thanks for all your research into this TDL!
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