Wheels, skids or fixed foundations: what each one costs you

People choose a foundation for practical reasons — cost, the site, whether they might move one day — and then discover it has decided their legal category, their consent path and possibly their finance. It is worth making the choice deliberately.

What is the difference?

Do wheels keep it out of the Building Act?

Only conditionally, and the condition is ongoing rather than a one-off. Section 8 of the Building Act includes as a building any vehicle "that is immovable and is occupied by people on a permanent or long-term basis". Both halves have to be true for it to become a building, but they are assessed on how the home is actually used, not how it was sold to you. Park it up, build a deck against it, plumb it in and live there indefinitely, and the answer can change over time without you doing anything deliberate. The full test is on tiny house on wheels.

What does each one mean for moving the home later?

A road-legal home on wheels under 2.55 m wide can be towed by anyone with the right vehicle and licence class. Anything wider, on wheels or not, moves as an over-dimension load: MBIE lists travel time restrictions, a route survey to make sure it will not get stuck, pilot vehicles, and possibly a specialist over-dimension transport company.

And moving a building onto a new site is not a neutral act. MBIE: "Relocating an existing building on an allotment is treated as an alteration to an existing building and as such will require a building consent for building work that is undertaken." So the second placement of a skid-mounted home is a consent job, even though the first one may not have been.

Which one suits which situation?

• You are leasing land or expect to move within a few years: wheels keep the option open, at the cost of a 2.55 m width ceiling and the ongoing need to stay genuinely movable.
• You have secure land and want a home you will live in indefinitely: skids or fixed foundations, on the building path, are the honest answer. Trying to keep a permanently occupied home in the vehicle category is a fight you will eventually lose.
• You want a granny flat on family land: that is Schedule 1A, and a dwelling on foundations. See the 70 m² granny flat exemption.
• You want a sleepout or cabin under 30 m² with no bathroom: a Schedule 1 exemption may cover it. See consent exemptions.

Does the choice affect specified intended life?

It can. MBIE notes that most buildings have a specified intended life of not less than 50 years, and that where you intend to live in a building for less than 50 years "you may consider designing and constructing a building for a lesser period". Under section 113 of the Building Act, a consent for a building with a specified intended life is granted subject to the condition that the building must be altered, removed or demolished on or before the end of that life. That is a conversation to have with your designer, not an afterthought.