Thursday June 18
MANY HANDS MAKE LIGHT WORK
With the pouring of the concrete slab scheduled only two days away a couple of extra workers were brought in for the day. Like the day before the weather was wet again, making things muddy and miserable. There was still lots of work to be done…
Once the sand is leveled to the correct height (or depth), plastic sheet is laid down. This forms a barrier for the concrete to sit on.
Warm from the ground up
The underside of the concrete slab is insulated with polystyrene to improve the overall thermal performance of the building. The concrete will provide much of the thermal mass and the insulation will reduce heat loss into the ground. The insulation is lightweight but rigid and comes in sheets that are easy to handle and can be cut with a handsaw.
The insulation sits on top of the plastic sheet and is strong enough to walk on. These sheets come with a tongue and groove that allows them to slot together for a snug fit. Like any insulation it is important to ensure there are no gaps that will allow heat to escape. Sub-slab insulation is not common practice in Tasmania yet but soon may be. The benefit of the sub-slab insulation became apparent when sitting on an off-cut piece on a stack of bricks – it kept the bum very warm!
Foot bone connected to the heel bone
The steel reinforcing that strengthens the concrete needs to be connected to each other: from the footings; up through the core-filled blockwork; and then into the slab. The vertical steel reinforcing from the footings/blockwork is bent by hand (with the aid of a pole and a brick to lever against) so it will sit flat within the concrete slab.
Where the concrete slab will be close to ground level there is no blockwork beneath it, and therefore no knock-out blocks to form an edge. Along these sections a length of timber is pegged to form a straight edge. This is known as form work, or boxing.
Part of the concrete slab will be set down 100mm lower than the rest – this will allow for a timber floor to the entry and wet area (shower base). Because the concrete will not be exposed in this area there is no need to insulate beneath it.
Costs: materials – $592; insulation – $1982
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.