Passivhaus Raft Foundations

Can you really build a house on that?  Will it not fall over?

These are just some of the comments from passers by down at the Killearn site as the Passivhaus foundations go down.  The reason being, there are two things people are not used to seeing:

1.  The passivhaus raft foundation system, where there is no need to dig into the ground as with traditional strip foundations.

It has been designed to be simply laid on well levelled ground, with the weight of the house evenly spread.

Levelling the ground is very important for passivhaus

Passivhaus insulated blocks

Sustainable Selfbuild coordinated the works to ensure that prior to the raft foundation being laid, the ground was measured and precision levelled.

Insulated passivhaus raft - no thermal breaks

Insulation, concrete and rebar in passivhaus foundation

Passivhaus Foundation – a well insulated and rebar reinforced concrete slab, on well levelled ground.

The raft means that there will be no thermal or cold breaks in the foundation, or walls, building on the airtightness of the house.  This is a very safe system, just not used enough in our opinion in the building industry.

2.  The insulated blocks for the passivhaus foundations –  helping to provide an envelope of insulation for the house.
These large white polystyrene blocks are filled in with concrete and rebar – and create a highly insulated concrete raft block foundation.

passivhaus foundation insulation

passivhaus polystyrene insulation, keeping U Values low

These polystyrene blocks will ensure the U-value of the house is very low.

passivhaus foundation weight spread evenly

passivhaus raft foundation – no need to dig down

As you can see, unlike traditional strip foundations, the raft is just placed on the ground. 

The house won’t fall down and by using both these methods – we can keep U-value (measure of heat loss) of the house very low, helping to achieve Passivhaus standards (or if that is not your intention, a very sustainable house build).

Watch this space as the Passivhaus timber frame will be put up next week.

For more information on building a passivhaus in Scotland, contact us at or call 07421763150, you could also check out The Passivhaus Trust.



Passivhaus Raft Foundations
Article Name
Passivhaus Raft Foundations
Description show the raft foundations for a passiv self build in Scotland. How to build your own sustainable house.

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