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The foldable house, anchored on the lawn on T-Block ground screws with no concrete slab.

Foldable house foundation: ground screws instead of concrete

A foldable house arrives folded and goes up in no time. The foundation is the first thing to prepare: with T-Block® ground screws there is no concrete to pour or to wait for, the house is anchored on the screw heads and, if you ever want to move it, the foundation unscrews and goes with it.

No slab
no concrete to wait for
Level
even on sloping ground
Unscrews
if the house moves

What a foldable house is

A foldable house, also called a folding house or fold-out house, is a prefabricated home that travels folded on a truck and opens on site: walls, roof and wings unfold around a frame. In a few hours it goes from delivery to a home you can live in.

The whole point of a foldable house is that speed, and the foundation is where it is easily lost: a concrete slab means formwork, pouring and weeks of curing before anything can be set on it.

Does a foldable house need a foundation?

Yes. You often read that a foldable house «sits directly on the ground», but manufacturers' installation guides say otherwise: they ask for level supports, in the right places, with drainage and wind anchoring. A folding house does not need a slab; it needs precise supports, and there is no better solution than a T-Block ground screw foundation.

  • Level supports

    If one point is not exactly at height, doors, panel joints and the roof suffer. That is why manufacturers ask for a level base.

  • Points under the frame

    There are several ways to give a foldable house a base to rest on; one of the best is a timber or steel frame set on T-Block ground screws.

  • Water that drains away

    No standing water under the house: a support raised off the ground lets water run off and air circulate.

  • Anchoring against wind

    A light house with a large exposed surface must be firmly anchored to the ground, especially in windy or coastal areas.

Ground screws for foldable houses, point by point

A T-Block® ground screw is a galvanised or stainless steel tube with a helix that is screwed into the ground like a screw into wood. A head is fixed on top and the frame of the house rests on it. Each screw is one support point, and each point is set exactly at height, because T-Block screws can be screwed in and out.

  1. The support plan

    We start from the manufacturer's sheet: where the frame points are and what the house weighs when unfolded and furnished.

  2. One screw per point

    A T-Block ground screw goes in under every frame point. The number and model are decided on the project.

  3. Levelled at the head

    Height is adjusted at the head of each screw: the house is level even when the ground is not.

  4. The house unfolds right away

    There is no concrete to cure: as soon as the screws are at height, the house is set down and you are done.

The calculation stays with the designer

Ground screws are covered by the Italian building code (NTC 2018) and by the codes of other countries. The configurator gives a first estimate, a hypothesis to be checked: the number and model are decided on the project, and the structural check of the house stays with the designer.

The guide to ground screws

Arona 2018: the first foldable house in Italy without concrete

In 2018 the first foldable house installed in Italy without concrete was built on T-Block ground screws: a timber foldable house on topsoil. Until then this type of house had never been anchored to the ground this way in Italy.

Mini excavator with a rotary head screwing a T-Block foundation into the lawn: an operator guides the screw, with the anchors already installed beside it.
Installing the ground screws in the lawn with a mini excavator.
The finished foldable A-frame timber house, resting on the lawn with no concrete slab.
The house assembled the next day.
Long side of the foldable house seen at lawn level: under the edge of the cladding, the row of T-Block ground screws holding the structure off the grass.
The long side: a row of ground screws, no ring beam, no slab.
Close-up of a T-Block ground screw under the side of the house: the plate at grass level carries the structure.
A single support: plate at grass level, grass intact all around.

The house rests on a row of ground screws along its two long sides, with the supports set at grass level. An open gap remains underneath: the timber never touches the soil, air circulates and the lawn stays a lawn. The full case study.

If the foldable house moves, the foundation comes out without a trace

A foldable house can be folded up and taken elsewhere: that is one of the reasons people choose it. With a slab, though, the concrete stays where it is and has to be broken up and disposed of.

Ground screws are unscrewed anticlockwise with the same equipment used to install them. If undamaged, they are reused on the new plot, and the old one is left with only the holes, which the grass closes. On rented land, farmland or a plot with restrictions, ground screws make the difference.

  • No demolition

    There is no footing or slab to break up: the foundation unscrews.

  • No concrete to take to landfill

    The ground was never polluted or consumed by concrete, so there is nothing to dispose of.

  • The foundation is reused

    Screws recovered undamaged are screwed back in at the new site, saving a great deal of resources, especially with AISI 304 stainless steel ground screws.

Slopes, wind and soil

On a slope

Each screw goes to the depth it needs and the level is set by screwing in and out, something that sets T-Block apart from ground screws with an almost conical body: the house sits level, safely, without moving the soil or invasive solutions.

In the wind

A foldable house is light with a large exposed surface. T-Block ground screws are the best in tension and hold it safely even when the wind really blows; sizing is done on the project, for the area.

On different soils

Lawn, earth, clay, gravel, sand: the length and model of the ground screw change. Rock is a special case, with special T-Block models outside the catalogue. Every soil has its best-suited ground screw.

Foldable houses and permits in Italy

If you are installing a foldable house in Italy, the honest answer is that the permit depends on how the house is used, not on it being foldable, and not on the foundation.

The Italian Building Code treats mobile homes and light structures, prefabricated ones included, as new buildings when they are used as dwellings, unless they meet merely temporary needs. Works for contingent and temporary needs, removed within 180 days, are free building works, with notice to the municipality before starting.

Italian administrative courts look at stable use, not at how easily the house can be taken apart, and require whoever claims a temporary use to prove it.

Ground screws do not exempt a house from permits. They make it removable without leaving concrete in the ground: consistent with a temporary or reversible installation, and much simpler to restore when the house leaves. Outside Italy, the rules are your country's.

Sources

What we need for your project

Have you bought a foldable house, or are you about to? Send us what you have: we reply with the support layout and the models suited to your soil, to pass on to your designer.

  • The technical sheet or support plan of the foldable house, with the frame points.
  • The size of the unfolded house and its weight, if the manufacturer states it.
  • Where the house will go: location, type of soil, slope, whether it is near the sea or in a windy area.
  • Whether the house will stay there or you plan to move it.

Do you make or import foldable houses?

If you manufacture, import or sell foldable or folding container houses in Europe, we can work out together a standard foundation layout for your models, to hand to your customers with the house. Write to us from the partners page.

Frequently asked questions

Do foldable houses need a foundation?
Yes. Even though a foldable house arrives folded and opens in a day, it has to rest on level points under the frame and be held down against wind. What it does not need is a concrete slab: ground screws, one per support point, are enough.
Can a folding house sit on the ground without a concrete slab?
Yes. With T-Block ground screws the house rests on a series of points screwed into the ground and adjusted in height. In Arona, Italy, in 2018, the first foldable house installed in Italy without concrete was set on the lawn this way.
How many ground screws does a foldable house need?
It depends on the house: we start from the manufacturer's support plan, with one screw under each frame point, and check against the weight of the house and the soil. The configurator gives a first estimate, which is a hypothesis: the number and model are fixed on the project, to the Italian NTC 2018 code or your local code.
How do you level a foldable house on sloping ground?
Each screw goes in to the depth it needs and the height is adjusted at the head, so the house sits level without digging or levelling the ground.
Is a folding house on ground screws safe in the wind?
Ground screws also work in tension: they hold the structure down when wind tries to lift it. Sizing depends on the area, exposure and house, and is done on the project.
Can the foundation be reused if I relocate the foldable house?
Yes. The screws are unscrewed anticlockwise with the same equipment used to install them and, if undamaged, can be reused on the new plot. Only the holes remain in the lawn, and the grass closes them.
How long does the foundation for a foldable house take?
There is no concrete to cure: the house goes on as soon as the screws are at height. In Arona the house was assembled the day after the foundations were installed.
Do I need a permit for a foldable house in Italy?
It depends on how the house is used, not on the type of house or the foundation. A house used as a permanent home is generally a new building; works for merely temporary needs follow different rules. Check with the municipality and your local designer: the reference rules, with sources, are on this page.
Do ground screws make a foldable house «temporary»?
Not on their own. Ground screws make the house removable without leaving concrete in the ground, but its planning status depends on its use and on local rules.
Has T-Block founded a foldable house before?
Yes. In 2018 in Arona we founded the first foldable house (an A-frame style foldable house) installed in Italy without concrete: a row of ground screws along the two long sides, with supports at grass level. The case is told on its own page.

More answers on service life, soils and permits in the FAQ.

Need a foundation for a foldable house?

Send us the house's sheet and tell us where it goes: we'll tell you which T-Block screws you need and how many.

Request a quote Use the configurator