Converting colourbond studio to granny flat

Hi All,

We intend to convert an existing 6m x 3m colourbond studio into a granny flat and we are looking for advice on how to adequately insulate the structure. The main purpose of the structure will be as an additional bedroom with en suite for family when they come to stay from overseas.

initially I had intended on using a 50mm or 75mm stud wall on the inside but I’ve realised we can’t afford to lose the space inside and now want to cladd the outside. The biggest issue I can see with this approach is that the footprint of the concrete slab is the same size of the current structure and I don’t know how to finish the external cladding to the ground to seal it from moisture and bugs etc. Looking for advice on products and methodology.

Any other tips would be greatly appreciated like on what product to use to seal the inside to the slab where there are gaps - expanding foam or silicone?

I have contacted council, a surveyor and an energy assessor so no issues there.

pictures and drawing attached. the concrete slab has a membrane underneath it.

Thanks in advance.

 

Did you fnd the foam inserts between the external/internal sheeting insufficient ?

 

Are you wanting to keep heat out or in?

To keep it cool, if it’s just for use as a bedroom every now and then, it might be easier to add an air conditioner.

Or add a ceiling fan and maybe another window on the back or side to encourage cross flow ventilation, which is very cooling. Could also have a powered extraction vent in the ceiling extracting hot air outside.

Add a layer of refelective foil , facing outwards, just underneath the cladding, on the inside to reflect radiant heat (ensure there is foil and batts in the ceiling too).

And/or keep the heat off the external walls, with a wooden screen, or blinds - or shade cloth over a frame. Or a vine.

And paint the entire thing with heat reflective paint.

 

Yes it gets very very hot inside and I’m guessing that they won’t be enough to meet the R codes. I have an energy assessor coming to advise.

 

keep heat out. The unit already has an air condition installed but we would need to run it a lot to keep the space comfortable. I’m also not sure if it will meet R codes. I have an energy assessor coming around to advise.

 

Is there an energy efficiency rating you have to meet?

I’ll be interested if it s a ‘tick the boxes’ thing or able to consider/promote
passive cooling solutions for efficient comfort - of which insulation is only one component…

 

Yea good point. I’ll let you know what they say, I’ll definitely be asking about passive solutions now - thanks!

 

In theory it's not going to be a granny flat (as per the rcodes) but you do want to make it more comfortable
Personally I'd give up that little bit of internal space and frame the inside as it's going to be a lot easier
The alternative is to use cool room panels on the outside as they are more sealed than putting cladding and insulation on the outside. You can attach an U shaped bracket towards the bottom of your current walls then slot the cool room panels into that so that they are sealed at the bottom. At the sides you don't have much clearance (especially where the downpipe is) so you may need to consider that. Though redoing the roof in cool room panels would also help and you can give it more eaves when doing that.

Something like this Brand New 50mm Trim Deck Cool/Cold Room Panel Roofing (CoolRoom) | Building Materials | Gumtree Australia Cockburn Area - Bibra Lake | 1164779917

Choosing a lighter colour will help, put some tint on the windows to help reflect heat

It may end up cheaper to actually replace what you have with a transportable donga than carve up what you have to put in a kitchen, ensuite etc

 

It seems like a lot of effort and expense to fit out what is essentially a shed. I like @Westminster's suggestion of a transportable donga, or even a caravan, instead.