Lots of good responses. Thanks. Some I had already considered but they have triggered some new thought in that area, and some I hadn't.
I was planning to do it myself, with assistance, hence the need to have a temporary weatherproofing arrangement prepared.
We're in West Gippsland so the extremes are not too bad, although it is getting hotter of course.
Adding another roof above and leaving the existing sheeting in place is an idea worth considering.
70mm is certainly not much when there is no air gap or sarking.
I had considered adding insulation against the underside of the ceiling but decided against it. Adding sufficient would lower the ceiling too much. If the roof was higher I would seriously consider filling the cavity between the deep beams with insulation and adding a new plasterboard ceiling below the beams. But that would reduce the ceiling height at the walls below 2.4m. The ceiling height at the walls is not quite 2.5m and it rises to the central main beam, but even adding 50mm under the ceiling would reduce the ceiling height more than I would like visually. I'm not a fan of low ceilings and the existing height is borderline to my eye. I'm also not a huge fan of exposed beams when the ceiling isn't high, but I find them acceptable if they are substantial. Adding any useful insulation between the beams will visually reduce their depth and that will have a negative visual impact in my opinion. However I do intend to add a sheet of plasterboard to the surface of the lining boards so we can have a smooth white ceiling.
I'll have a search for those new systems with insulation bonded to corrugated roof sheets.
I hope we're there for another 20 years - deteriorating in place.
The roof sheets must be 25 to 30 years old now (we've been there 17) and some require replacement due to corrosion below things like the wood heater flue and TV mast. I had assumed that I would be replacing all sheets when the time came as I want to eliminate 2 old skylights and other roof penetrations.
The old spring-head nails are now loose due to timber shrinkage and movement and should come out without too much effort or damage.
New spouting will be needed and all flashing and the ridge capping would be replaced anyway.
I'll be sticking with uncoated Zincalume, not Colorbond. Apart from its better reflection I'd still rather drink water off an old zinc and aluminium roof than an old Colorbond roof, despite the fact that Colorbond has now been around for a very long time.
We are planning an extension and after that there will be no penetrations through the existing building's roof, and no TV mast. The PV array currently on the roof will be relocated to another building.
After reading all your suggestions I'm beginning to think that the way to go is to remove the current sheets a few at a time, fix the insulation by adding more and filling the gaps, then refitting the existing sheets. Then, after the extension is finished, add battens, more insulation and new roof sheets above.
Posted Wednesday 2 Dec 2015 @ 12:18:18 am from IP
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