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Hi there, loving this workshop forum!
Like others, I've been reading through a bunch of posts to see if there were already answers to my questions but couldn't find anything that covered the lot so I've started this new post. Hope that is okay! We are 5 years into a 1-year renovation plan and one component has been replacing joists, deck boards and handrails on our verandah and adding insulation and a ceiling to stop condensation (which is prolific) and make it cooler in summer. We are not quite done with the decking, but getting close. Because we have painted posts, beams and rafters which will require re-painting, we need to decide on the insulation and ceiling options to use so we know which beams/rafters will remain visible.
We have a three-sided wrap round deck with bullnose roofing (each side is 4m long and it's 17m long on the front). From exterior house wall to outside deck facia beam, it's around 2.0m long. There is absolutely nothing consistent about the spacing between the rafters - or anything else about our house for that matter - so sadly, it's not a matter of simply buying 900mm wide insulation panels and slipping them in between each. Spaces between rafters range from 780 to 880 (I think, haven't measured them all). Power runs along one of the rafters and is then channeled on top of the facia beam (under the roof) to 3 or 4 flood lights that are also attached to same along the length. The corners, where the hip rafter is, might make installing insulation and a ceiling complicated? Photos are attached. I was thinking that the simplest ceiling option is installing insulation close under the roofing somehow, then slipping the ceiling panels in above the facia beam (where it would sit above) and screwing the panel into the bottom of the battens. This would leave most of the rafters exposed, but not the battens.
My questions:
- Is there a good insulation option (like foil board or Aircell or some other product that is waterproof) that can be easily cut to size and installed directly under the colourbond within each rafter space?
- If so, how would we attach it if we are not removing the bullnose to sit it on top of the rafters? Can it sit on the ceiling panels, or does it have to be close under the bullnose? We get heavy condensation, so it needs to be rot/water/mould proof or effective enough to stop the condensation.
- What would be most cost effective, easy to fit, mould-resistent ceiling panel options? Hardie-board?
- Is it okay to fit them into the rafter spaces as I've noted above, or should we simply install ceiling panels in large sheets on the lowest points (bottom of rafters) with all the joins running paralell with the deckboards?
If you think this belongs on a different 'board' or I need to seek help elsewhere, it's totally okay to let me know. I have some other questions relating to installation of french doors where our bay windows used to be and I'll place that on the 'Whole of House' board.
Thanks, Michelle
Hi @Bells67
Your very welcome to ask question here any time.
Well I note your condensation issues.
Ps I love your bull nose verandah and new deck.
Insulation
I am not sure how you will benefit from any insulation you add there ?
Your thinking insulation so you might be getting high radiant heat from the tin during the day.?
If you can confirm that possible assumption?
Any how lets talk insulation and your bull nose roof shape for now just talking out loud to get your thoughts back.
Foil roof sheeting can be heat reflective to help reduce the heat of the metal roof getting through. Another type has foam inner core that adds more heat blocking properties x3 $. I am thinking it can be glued to your metal bull nose and follow its shape but I might recommend unscrewing middle rafter screws to allow a single sheet to run above that rafter. Option 2 You may wish to run to that middle rafter along the under roof line and encapsulate the middle rafter from below (down one side across the bottom and up the other side back to roof line.) So no roofing needs undoing.
I would start the sheet near the house and attach on the underside of that first rafter then over the top of the middle rafter (or encapsulate it) then spot glue to the bullnose curve with the insulation at the end bending back reversing on itself pointing inwards at the house and it is stapled on top of that beam for easy attachment and access.
I think this would look the neatest and provide best coverage for inside the bull nose
Foil boards or foam non foil versions for NZ may be hard to fit in bullnose shape you may end up with flat angle between middle rafter and outer beam. Not as visually appealing as bull nose.
Well your Idea to add a villaboard (hardiboard) under the roof rafters will work you can use any insulation above it including batts. you will have to add some more timber to support sheeting. Insulate as you go. This works well as the big air gap above will help clear condensation. Where as foil sheeting will not have a much air gap if at all . It wont hurt insulation but continuous mositure can lead to issues it should drip near outer roof beam if it does
All the insulation is water proof and has fire /ember resistance Batts will hold water and can go moldy if continuously allowed to get wet redripping condensation ? (not in your case though.)
The electricals should be below potential insulation points so is ok
Yes that corner is always a joy to do just need to add timber above optimal sheeting joins.
Dosnt matter which board you post on they are all seen in this common board area, 
Well lets talk and others can join in too.
A very warm welcome to the Bunnings Workshop community, @Bells67. We're delighted to have you join us.
Your renovation projects sound exciting and we look forward to being part of your journey. As @Jewelleryrescue mentioned, please feel free to post questions anytime you need a hand. Our wonderful community members are sharing projects and exchanging handy advice on the site every day and I'm sure they'd be happy to assist. Do let me know if you need a hand getting the most out of the site and understanding how to navigate it.
Great to see you've received some advice from @Jewelleryrescue about insulation and ceiling options for your verandah. Let me also tag our resident Bunnings D.I.Y. expert @MitchellMc, who will also be happy to share his thoughts as soon as he can.
Feel free to post questions about the installation of your French doors in the meantime. Don't worry about selecting the right board. We can always edit your post from our end and move it to the correct board if needed.
Welcome once again.
Akanksha
Evening @Bells67
Definently an interesting question And yeah the perfect place to ask.
Woooo What a kettle of fish this question is! I just went looking to see how others may have solved it. Pretty sure I would have traveled the same path as you
Well two things I was going to suggest (foilboard or air flow via a fan) look like a no go as well.Found a bunch of information here metal roofing and condensation (It is an outside company that I havnt used but the condensation info at the bottom of the page is worth a read)
Sarking sounds like a winner as in redirecting the condensation drops. I am just racking my brains on how to install it without removing the tin. (I dont have sarking on my tiled roof either 😕 )
Outside the square thinking at the moment, you know that spray foam? I wonder if you used that on the underside of the tin, if it would insulate enough to stop the condensation forming underneath? There would be no air gap for the moisture to form. I have seen videos of people spraying this type of foam stuff for insulation in their walls but not exterior roofs. Also not sure how pretty it would look plus the fire rating of the product and that would be my biggest concern for any of the ones I have mentioned.
So Sarking is still my prefered option for channeling the condensation more then actuall stopping it. 😕
Dave
Thanks so much for your advice @Jewelleryrescue
You are spot on - while condensation is a large problem that we want to solve (very big droplets that soak everything!) it is mostly the radiant heat factor. We've been doing some testing through the recent heatwave. We have a similar deck on the southside (just not bullnose) and then the bullnose wrap-round on the other side of the house. South side gets the afternoon heat and bullnose gets the morning sun. Early morning on the hot days, it was 23 degrees on the back deck and 37 degrees under the bullnose. This reverses a little in the late afternoon, but the bullnose section seems to retain the heat. We thought that insulating might keep the radiant heat down a bit.
Really appreciate your advice about attachment - both options feel do-able so I'll look into costs for those two insulation options. @Dave-1 also very kindly suggested spray on insulation so that could work (and if we install a ceiling, it wouldn't be visible).
I think we may live in the mould capital of South East Queensland here, so anything that can get mouldy when damp will be avoided, just in case.
The thought of adding additional timber hadn't occured to me, but we are well and truly able to do that, so thanks for that tip!
Cheers,
Michelle
Hi @Dave-1
It has been a bit of a quandry for us that is for sure! You might have seen my response to @Jewelleryrescue - the heat under the deck is crazy when compared to the actual temp outside in the yard itself and the condensation soaks everything.
You are correct in saying stiff foilboard is not ideal and we can't really install fans under our deck - not enough clearance. I've been looking at sarking options following all the wonderful advice I've been receiving - there seem to be many types available, but most state that the sheet needs to be installed with continuous contact to the metal which we won't be able to do without removing the bullnose roofing. (Great link you provided, thanks, as I've learned some things about sarking and insulation I wasn't aware of).
In terms of the radiant heat problem, I'm keen to know whether the thermal benefits of sarking disappear completely if the sarking is cut to fit between battens/rafters. (I'll certainly investigate the spray-on option as well).
As @Jewelleryrescue suggested in option 2, after a bit of reflection today, we think we could run the sarking paralell to the house wall from the batten closest to the house to the middle batten - this is around 1200mm wide (ie. not much wastage). The distance from the middle batten to the top of the facia beam is around 700mm, so we could make efficient use of the 1500mm sarking roll option by cutting in half lengthways. We would have to spot glue to attach. The question is whether we should go with straight sarking, or something like kingspan aircell / ametalin thermalbreak which is still flexible and moulds to the roof but has additional thermal qualities. We thought that builders blankets, which have the foil as well as wool insulation would be no good as you couldn't glue the wool side to the metal roofing easily. Any thoughts on this would be very welcome.
Unfortunately, all this wonderful information has made it abundantly clear that our under-house-roof insulation is also woefully inadequate! No sarking at all and insulation batts lying on the ceiling that were made in the 80's. But that is another problem for another time!
Thanks so much!
Michelle
Afternoon @Bells67
Yeah, sounds like you guys are in my mind about insulating lol Older Australian houses went built to insulate and the rules didnt catch up for years!
I have no sarking,
I have plaster ceiling but it has reflective stuff on the ceiling space side.
There is also half pulled out insulation that looks likeit may have been wet so they pulled it out and did a shoddy job....
So tempted to bite the bullet and switch my tiled roof to a tin roof with proper insulation.
So the question I have for you, If you are renovating anyway, how much effort/cost would it be to slowly pull up the bull nose and fit insulation under it plus associated timber work or replace the vull nose with a straight run off to reduce that heat catching ability?
I costed my roof (in my head a few years back) and it would have been 25-30k So now Id say 45k and thats before id get a quote. Overall cost/issues sometimes will switch a renovate to replace which I am sure you have already come up against
Looking forward to seeing how you solve it, There are so many threads regaurding insulating existing underside tin roofs but none have really solved it to stop condensation forming.
Dave
Hi @Bells67,
It's great to see you've received some excellent advice from our helpful members. So that you know, the droplet issue you're dealing with is due to moisture-laden air at the dew point coming in contact with the roof sheeting. The water then condenses on the sheeting, and forms drips. If your intention is to clad under the rafters, then that excludes the moisture-laden air from reaching the underside of the roof sheeting. So, once you sheet and insulate the space, there will hopefully be virtually no ability for droplets to form in the cavity. However, I'd certainly consider using Gyprock Aquachek or a similar water-resistant sheeting.
Mitchell
hi @Bells67
Given what you kindly replied back with that tin gets mighty hot to hold all that heat I now strongly am leaning towards ametalin thermalbreak as the foam sandwich will block the heat coming through during the day and afterwards.
Any mould up there should be destroyed by the heat. I think putting in a villawood ceiling wont work in QLD humid heat.
So using thremal break I propose two methods of attching to under roof , Over the middle rafter or under stapling it or gal flat head nails, (Blue nails or staples or both) Staples use will help hold it in place before nailing. Spot glue liquid nails (red spots) will help it follow roof lines.
