That’s a wrap
Once the roof was on it was time to wrap the building. This used to be done using ‘building paper’ – similar to the sisalation installed under the roof, building paper has a reflective side and a matte side. The reflective side either faces inside to keep warm air from escaping the building or faces outside to prevent hot air entering the building – this depends on the climate zone.
Advances in mechanical heating (heat pumps), combined with buildings becoming better sealed (for energy efficiency), have led to an increase in condensation. In the past the temperature difference between inside and outside was not that much, there were more draughts in buildings, and people used to open windows and doors for ventilation to ‘air out’ buildings. Now many people sit inside, crank up the heat pump and don’t open windows for months at a time. The warm, moist air has nowhere to escape to. Condensation forms and sometimes results in mould. Yuk!
There have also been technological developments in building materials, including thermal blankets and vapour permeable membranes. Think of a really good rain jacket, the super expensive type – the type where it can pour with rain and you don’t get wet, from the outside or the inside. Even if it’s hot and you’re moving around the sweat magically escapes – the material ‘breathes’. I’ve never owned one of these jackets before (they are expensive) but know they exist and are very good. Technology such as this now also exists for buildings. The walls of 60k House are clad in a vapour permeable wall wrap – it protects it from outside water, is air tight trapping heat inside, and allows moisture to permeate from the inside to outside.
Blood, sweat and tears
Fixing wall wrap is quick and easy – so quick I hardly got any photos! The wrap can either be measured and cut, or kept on the roll and pulled tight as you move along the building. The wrap is then held in place with foil fixers – the sharpest objects known to man! These fixers come in strips and bend off once the end one is hammered in to hold the wrap. Plenty of blood, sweat and tears have gone into 60k House, particularly Greg’s blood…
A few days after wrapping the building there were some very high winds – typical for spring in Tasmania. This ripped a couple of patches of the wrap off the wall frame. It’s advisable to always cover the wrap as soon as possible because of this reason (and possibly UV exposure).
All of the cladding above 2130 (2.13m) is 4.5mm thick cement sheet. The height is not arbitrary – the height is determined by the size of the four large windows, which corresponds to slightly higher than a standard door, and is also roughly three apple crates high. This datum runs right around the building. Below this datum the cladding will be either 6.0mm thick cement sheet (higher chance of impact), timber weatherboards (the apple crate reference), or windows.
The cement sheet (and in fact all of the cladding) is battened out on 35mm thick timber battens. This creates an air cavity between the cladding and the wall wrap that improves thermal performance and provides a space for any water (from either inside or outside) to drain to.
It took roughly one day each to clad the high parts of the four sides of the building. Most of the time spent was setting up the battens to ensure they were level – pine framing sometimes moves, especially if it has been exposed to weather (which it was before the roof and wrap went on).
There is a slight step at this height caused by a change of depth in materials. This step means a flashing (folded piece of metal) is needed to shed the water outside. The flashing runs behind the cement sheet and over the front of the material below (window, cement sheet or weatherboard).
The cement sheet won’t get painted. That’s it. Actually it will get a clear seal finish to prevent it soaking up any water at the edges, but it will still look the same. And it will also get some timber cover strips for extra protection. But apart from that it’s finished. I like to use natural materials and leave them expressed – don’t try to hide or colour them.
Costs: framing timber – $594; flashings – $170; fastenings – $384; cement sheet- $474; builder – $3,770
Disclaimer: Any advice contained within this blog is of a general nature only and cannot be relied upon. Details provided are in good faith and relate specifically to this project. Any author will not be held responsible for advice or information presented.