A factory-built cabin or sauna does not need a heavy foundation. It needs a level, stable base, an air gap underneath and, on exposed sites, a firm connection to the ground.

Most Brette Haus and Æqua units do not need a slab. On level ground they stand on concrete piers, or on a few concrete blocks laid on levelled, compacted soil. Ground screws make sense on slopes, on uneven sites and for seasonal cabins. Whatever the base, keep at least 15 cm of clear space under the floor so air can move and the timber stays dry.

Concrete piers. Our default for Tiny D, Rustic and Æqua on level ground.
Concrete blocks on compacted soil. The simplest option on firm, flat ground: level the soil, compact it and lay the blocks where the support points fall.
Ground screws. For slopes, uneven sites and seasonal cabins. They need no concrete and come out again if the building moves.

A full concrete slab is rarely needed. It costs more, takes longer and closes the space under the floor that the building needs to breathe.

Leave at least 15 cm of clear space between the ground and the underside of the building. Air moving under the floor keeps the timber dry; without it, moisture collects and the floor structure starts to rot. With less than 15 cm, our warranty does not apply. If you add skirting around the base, leave openings so air can still pass.

The support points must be level within 5 mm per metre. Our team carries thin shims to correct a larger deviation on installation day, but it is better to check the levels before the truck arrives. A Rustic rests on 12 support points: six take the folded building first, and six more take the Dropout module when it is unfolded. The technical passport for each model shows where the supports go.

Rustic: about 10,500 kg.
Tiny D: about 3,500 kg.
Æqua Cella: about 2,800 kg.
Æqua Core: about 2,400 kg.

Weights change with the specification. On soft or uncertain ground, ask a local engineer to check that the soil can carry the load at each support point.

Weight alone does not hold a building down. In February 2023, a storm on Lofoten in northern Norway swept a modern holiday cabin, about 14 tonnes, made by another manufacturer, off its concrete piers and onto the rocks by the sea. The guests inside were injured, and the police investigated whether the cabins had been built as they should have been (News in English).

Cases like this are rare. Still, on coasts, open plateaus and mountain sites the building must be fixed to its foundation. Ask a local engineer how the anchors should be sized for the wind loads at your site.

One more rule for metal supports and anchors: do not use them to earth the building's electrical system. The metal will corrode fast.

Make sure rain and snowmelt drain away from the supports. On a sloping site, water should not run under the building and collect there; shape the ground or add a drain so it flows past.

The foundation is prepared by the client, usually with a local contractor, before delivery. We provide the support layout for the model. For slopes, poor soil or exposed sites, bring in a local engineer. On installation day our team checks the levels before the building is set down.

Read what happens on installation day in From Factory to Unfolded. See Tiny D, Rustic and Æqua.