Advice on insulating an attic space in old Queenslander cottage

Insulation is a tough area. There are people on here that know a lot about it and hopefully that can guide you. A couple of comments ...

How deep are the rafters?
Is there no existing blanket or foil under the tin? This could be a challenge, it can be retrofitted from below for thermal purposes but that will not help drain condensation.
There is a lot of discussion about whether sound rated insulation and plaster is worth the extra money ... or is it like the price hike that comes with putting the word 'wedding' or 'baby' in front of a a product?

One key thing for sound is that it will find any gaps and undermine your whole plan, so whilst it's open it'd be worth filling any holes with filler, foam, etc. to help seal it out. The way I think about it is ... sit in your car (you don't need to be moving) and it's fairly quiet, open the window just a crack and all of a sudden you have all the outside noise, open it fully and you have only a bit more noise. The point being that the tiny crack let in the majority of the noise. It's not the whole solution but it's cheap and easy whilst the roof space is open.

Hi OBBob,

Thanks for your quick response. The rafters are 100mm. It's a very old house so whilst there are in pretty good shape considering the age, there is a bit of variation in them.

In terms of blanket or foil under the tin - there is absolutely nothing. We've been in the house for ~6 years now and it gets very cold in winter and very hot in summer!

Also given the age and type of the house - yes there are lots of gaps. E.g. in the gables there are some pretty big gaps between some of the weatherboards. I was going to use some 'no more gaps' or similar to fill them.

Thanks,

Barry

Something else that may be relevant (I'm not too handy so please forgive me if I get my terminology wrong...)

The horizontal battens are spaced at roughly 300mm. But the iron roof is not attached to all of them. There is a 'double thickness' batten approx every 700mm which the iron roof is attached to.

So we did consider whether we could run 'anti-con' between these battens. The gap between the iron roof and the battens is ~30mm. I don't think that is enough space to install anti-con?

Originally Posted by Marc

... and they will take up the good part of one room below. ...

And often upstairs because they need to be central to achieve the headroom requirements.


On the thick and thin battens, is it possible the house originally had tiles, which were replaced with tin at a later time?

OBBob - yes, someone has said to us that it is likely we had a tile roof at some point in the past.

Regarding stairs / headroom, etc - we're not planning on getting the attic certified as a live-able space. Because of the pitch of the roof the room would have to be very narrow to get the required ceiling height.

Originally Posted by grizzlyscotsman

OBBob - yes, someone has said to us that it is likely we had a tile roof at some point in the past.

Regarding stairs / headroom, etc - we're not planning on getting the attic certified as a live-able space. Because of the pitch of the roof the room would have to be very narrow to get the required ceiling height.

Hmm... I guess you're aware that it's not really meant to be optional to certify it as habitable if you're using it for a bedroom and bathroom? It's up to you how you progress but carefully with insurance and implications of you plan to sell in the next seven years.

It might be worth reading up on the habitable requirements because I think you can average the ceiling height across the room, which may allow you to achieve a feasible / legal design.

Spray foam as Marc suggested might be a good option. I think there are even DIY kits if you're keen.