our roof

Our roof has been on for a little while now and this is how we went about installing it:

We decided to go for the “classic cream” colorbond colour, as it seems to perform pretty well in the hot Australian sun. This table shows a comparison of the thermal efficiency of the different colorbond colours, which means how well they absorb radiant heat (the fancy term for this is "adsorptance"). Not surprisingly, the darker the colour, the more heat it absorbs. While we really liked some of the darker colours, we weren't too keen on having a super-hot roof, so we took our pick between "classic cream" and "surfmist", which have the one of the lowest ratings. The only lighter colour there is is called "whitehaven" but it wasn't available through our supplier yet and we also thought the very bright white might be blinding potential future neighbours. The last thing we want is to be an eyesore to anyone!

Up on the scaffold, getting ready for some roofing!

We got our corrugated sheets delivered together with our custom-made flashings and the pile of roofing material looked surprisingly small! After we put the rafters on, we covered the ceiling with a layer of breathable house wrap, which we will be putting around the outside of all our wall frames as well. We thought it would be a good idea to ventilate our roof cavity, so the hot air will not simply be trapped underneath the corrugated iron. To do this, we raised the battens by a few centimetres with little blocks. Even though every single cm in our tiny home will be valuable real estate, we thought that it would be worth "loosing" 4cm in height to hopefully have less heat coming in during summer. We’ll see how well it works. 

Our ventilated roof cavity. From bottom to top, there are rafters
(not visible here), housewrap, blocks for extra spacing, rafters,
anticon and corrugated sheets (also not visible).

We were a little worried about the chance of condensation occurring underneath the corrugated iron in winter, which could lead to issues such as mold or rot down the track. We got a product commonly know as “anticon” (we got the Knauf brand Space Blanket), which seems to mitigate the chance of condensation under the roof. It sits above the roof battens and below the corrugated iron sheets and depending on what brand you choose, it consist of either fibreglass or mineral wool lined with a reflective foil on one side. 
The raised battens should create a big enough cavity below the anticon for its reflective layer to work to its full extend. Wherever the silver foil touches another material, it will just end up working as an unwanted conductor of heat and cold, instead of reflecting the radiant heat. So we took great care that the anticon didn’t sag too much during installation and hopefully it will stay in place over time.

Cutting the anticon to size

A builder friend advised us to make sure to get the first corrugated iron sheet as parallel to the long side of the house as we could (thanks Zev!) and we put a string line across the front of the house to make this job easier. Apparently things can get out of hand pretty quickly if the first sheet isn’t lined up correctly, as any errors made with the first sheet only get worse down the track.

Aligning a corrugated sheet with help of a stringline.

The first sheets are up - time for some rest!

It took us a little while to get our head around what flashings we needed for the roof. We were a little concerned that our low roof pitch could cause rain water to get into our build between the corrugated iron and the gutter, so we decided to install a gutter apron. This should direct rain water that runs off the roof and that might get blown towards the build, straight into the gutter. We’re still not too sure if that was necessary or not though.

For the other three sides, we picked some standard barge capping and used infill strip to stop water from driving rain also insects getting into our roof.

The little bay roof took a lot of fiddling around and even though it is tiny, it took a lot longer than doing the big roof! We think it was totally worth the time and headache though, as we are in love with our bay window already! 

We calculated that the "standard" treated pine fascia boards available would add up to around 70kg, which we decided would be too heavy. So we painted some of the very light weight western red cedar boards we bought for our cladding and to make them stand out by painting them teal. It just made things a little tricky, as they were bevelled, but we are pretty happy with how they turned out! Thanks to Ines and Tabea for your help :) 

The roof from below. The gaps between the rafters will be filled with insulation

Tabea doing some touch-up work on the fascia boards

Barge capping to cover the ends of the corrugated sheets

The little bay roof

A corner of our bay roof