The main four processes involved are illustrated below:
|The system consists of clearing the top soil to 600mm below finished floor level, then covering with compacted hardcore.||On top of this expanded polystyrene blocks are laid around the perimeter, followed by polystyrene sheets inside the building.||On top of the polystyrene, steel mesh is installed along with under floor heating pipes if required.||
Once everything is in place the slab can be poured which forms your finished floor screed.
The passivhaus version provides a thermally bridge free foundation, or the less costly version a very efficient solution.
The drawings below shows the thermally bridge free passivhaus foundation version which has the outside of the timber sole plate supported by a thermally separated ring beam to the main slab so there is minimal thermal bridging through the sole plate / slab interface. Alternatively, a solid sole plate can be used which can overhang the polystyrene for a passivhaus solution:
- Concrete in foundation is all warm side of the insulation
- Quick to install once the site is prepared
- Simple / elegant
- Various options varying in price, down to passivhaus thermally bridge free options
- Specialist process
- Surface power float finished ready to be tiled / carpeted – no screed
- Expensive, particularly the passivhaus version
- Not suitable for certain ground types – shrinkable clay for example