Bottom Up

From yesterday's comments I see that our house construction methods are a novelty in some other parts of the world.

Designing a house here comes with options. From the bottom up - the foundations - one could choose a number of options from piles, poles, concrete slab, to rib-raft (and stuff in between).

Our house is on a rib-raft; a design developed/ improved and more widely adopted after the 2011 earthquake in Christchurch.  It's 400mm (about 16 inches) of polystyrene and reinforcing steel (sitting on 700mm of compacted hard-fill) and encased in concrete. We also have pipework in there for underfloor heating.

On top of that rib-raft wooden frames go up for the walls. They are from 90mm to 140mm thick depending on how much insulation you want. Ours are 90mm.  Wooden roof trusses span the tops of the walls.  We might have gone for an open raftered ceiling but the engineering involved for our design made the cost prohibitive (and the rooms would have been more difficult to heat if I'm realistic about it).

Once the frames are square, level, vertical etc. the outside of our house and garage was wrapped in plywood, then an anti-condensation membrane, then battens applied and finally the corrugated iron will go over that. Houses that are clad in wooden weatherboards, bricks, limestone, concrete blocks, exterior plywood or board and batten designs are built the same way out to the anti-condensation membrane.  I chose corrugated iron for the walls because it requires no maintenance compared to wood, and is considerably lower cost to buy and transport out here than brick or stone.

Because of our earthquake risks modern houses are only clad with brick or stone; it isn't a structural material as such.  It is the wooden frame that holds up the roof. 

House could have steel frames instead of wood but we have lots of wood and steel frames are expensive.

Long-run (meaning long pieces) of roofing iron comes in a variety of profiles (different wriggles). That sine-wave wriggle that we have chosen is the oldest, original version. Most domestic roofs in NZ these days are long-run iron. That's our tradition I guess.  There are tiled roofs (1950s mostly) and I had a house in Dunedin years ago with a Welsh slate roof but that must have cost a bomb to import when it was built in the early 1900s.

Roofing comes in a range of colours so you don't have to paint it. Coloursteel for example.

The windows for our place are 'thermally broken' aluminium frames (meaning inner and outer frames are separated by a thermal barrier to stop them being a heat conductor), double glazed, and thermally recessed (means we have no windowsills on the inside because the windows line up with the insulation in the walls - not with the cladding on the outside of the building).

Once the building has reached lock-up stage we can start on the inside. First the fibreglass insulation goes into the walls; into the cavities in the wooden frames.

(In case you are wondering, the garage is 2 storeys - studio at the top and Mr B's workshop at one end of the ground floor. That's why it looks so big.)

Wall mounted radiator heating is virtually unknown out here - certainly the reticulated hot water kind. Most people these days install heat-pumps. We will have solar-thermal water heating supplemented by a wood burning fire (actually inside the hot water tank) for the domestic hot water and under-floor heating, and a fireplace in the living room for a 'hearth at the centre of the household'. I believe in systems back-ups. It's a fireplace we could cook on if electricity failed. (In any event we'll need a back-up generator because power failures out here can last days or weeks when they happen.)

Things have stalled while we wait for windows to arrive. They have to go in before the exterior cladding goes on apparently.