Expandable Home Foundations: Separating Facts From Fiction

Modular Myths & Tiny Truths, Edition #2

Expandable homes are growing in popularity across Australia as buyers search for affordable, fast, and flexible housing options. However, with that growth comes confusion, especially around one of the most important questions in the entire approval process:

“Do expandable homes need foundations, or can they just sit on the ground?”

Some suggest foundations are optional. Others claim councils do not allow expandable homes at all. The truth sits firmly in the middle and is backed by legislation, engineering standards, and real approvals.

This guide separates fact from fiction and helps you understand exactly what is required to install an expandable home legally, safely, and with confidence.

The Short Answer

If your expandable home will be approved and occupied as a Class 1a dwelling, then yes, it requires engineered foundations. This is required under the National Construction Code (NCC) Housing Provisions (ABCB).

Only temporary or movable dwelling classifications may avoid fixed footings, and even then, anchoring and safety rules still apply.

When someone says “no foundations required”, they are usually referring to:

• temporary installation only
• non-Class 1a occupancy
• a product that is not engineered for permanent habitation
• a sales-driven simplification
• being deceptive

Myth #1: “Expandable Homes Are Exempt From the NCC Foundation Requirements”

A common myth suggests that because expandable homes arrive prefabricated or fold out on site, they somehow bypass the National Construction Code.

Truth: If an expandable home is assessed as a Class 1a dwelling, it must comply with NCC Volume 2, including structural, wind, footing, bracing, waterproofing, and energy-efficiency requirements (NCC Housing Provisions).

This includes:

• Wind loads: particularly Regions B, C and D in QLD
• Structural design actions: per AS 1170 (loading)
• Footing and slab systems: per AS 2870 (residential slabs and footings)
• Weatherproofing and water ingress prevention
• Energy efficiency compliance

For a deeper breakdown of approval pathways, read our evidence-based guide: Can You Get Building Approval for an Expandable Home?

Myth #2: “You Can Place an Expandable Home Direct on Level Ground”

This myth creates more failed approvals than any other. Some foreign sellers advertise “no foundation required” to simplify the sale, but this only applies to short-term temporary installations. Permanent dwellings require a compliant footing system. Likely because their service ends when they drop it off at your property, leaving you to deal with it.

Truth: Permanent installations must use engineered foundations that support structural loads, resist wind uplift, manage soil movement, and comply with NCC Volume 2, Part 3.2 (ABCB).

A compliant foundation system must withstand:

• Wind loads: especially in cyclone-prone regions
• Uplift forces: lightweight structures require secure tie-downs
• Soil movement: as defined in AS 2870 soil classifications
• Dead and live loads: including furniture and occupants
• Long-term settlement: important in clay and fill areas

Common compliant footing systems include:

• Concrete piers: widely used, cost-effective, and well supported under AS 2870
• Steel stumps or adjustable footings: ideal for sloping sites and reactive soils
• Screw piles: commonly used under engineered stump systems, particularly on difficult sites
• Perimeter footings: often required for container-based or hybrid expandable homes
• Concrete slabs: occasionally used for permanent installations when engineered for load paths

Uncommon systems where compliance may be achieved via a Performance Solution:

• Engineered skid or rail systems: not recognised as a standard footing method under AS 2870, and therefore require a Performance Solution supported by structural engineering and certifier approval

Skid or rail systems are not referenced as a Deemed-to-Satisfy footing solution in the NCC or AS 2870. Where used for Class 1a dwellings, they must be assessed and approved as a Performance Solution demonstrating compliance with the NCC performance requirements.

Non-compliant systems include:

• Resting the home on loose concrete blocks
• Using unanchored or non-engineered skids
• No tie-down or uplift engineering
• Any footing system lacking Form 15 and Form 16 certification where required

Why Many Sellers Say “No Foundations Needed”

You may see this phrase in advertising or social media comments and especially Facebook Marketplace. It is not technically wrong, but it is rarely explained properly.

Sellers say this when:

• They are referring only to temporary use
• The home is not engineered for Class 1a compliance
• They assume the buyer will not seek council approval
• They want to advertise a simpler, cheaper installation

A registered builder understands the national construction code, I can’t think of any situation where a builder would say foundations are not required.

This is a major reason Tiny Home Quotes remains independent. Our priority is compliance and long-term safety, not simplifying requirements for marketing purposes.

Myth #3: “Foundations Are the Same Across Australia”

Foundation requirements change depending on state, local council, wind region, and soil conditions.

• QLD: cyclone regions require high-strength tie-downs
• VIC: reactive clay soils require engineered footings
• NSW: movable dwelling regulations only apply when the home is not Class 1a
• WA: northern regions experience extreme wind conditions

Soil classification must also follow AS 2870, which may require a geotechnical report.

This is why advice on social media often contradicts itself. People are referring to different rules in different environments.

Foundation Options for Expandable Homes

Foundation Type	Cost	Best For	NCC Compliance Pathway
Concrete Piers	Low to Medium	Most expandable homes, uneven or reactive sites	Yes, Deemed-to-Satisfy when engineered
Steel Stumps / Adjustable Footings (incl. Screw Piles)	Medium	Sloping blocks, poor soils, QLD wind regions	Yes, Deemed-to-Satisfy when engineered
Perimeter Footings	Medium to High	Container-based or hybrid expandable homes	Yes, Deemed-to-Satisfy when engineered
Concrete Slab	High	Permanent installations with suitable soil conditions	Yes, Deemed-to-Satisfy when engineered
Engineered Skids or Rails	Low	Limited scenarios only, site-specific designs	Performance Solution only, certifier approval required

So, Do Expandable Homes Need Foundations?

Yes, if you want the home approved as a permanent dwelling.

Foundations may not be required only when the home is installed as:

• a movable dwelling under state legislation
• a temporary structure
• a non-permanent installation not connected to services

However, these pathways come with major restrictions, including limited occupancy rights, lower insurance suitability, and reduced resale value.

The Tiny Truth

Expandable homes are not exempt from NCC requirements, engineering standards, or foundation design. They can absolutely be approved, but only when installed correctly and safely.

A compliant installation requires an understanding of wind regions, soil types, engineering requirements, and local council rules. Cutting corners here often leads to delays, rework, or costly failures.

Want a Compliant Expandable Home Without the Guesswork?

Tiny Home Quotes helps Australians connect with vetted, NCC-ready builders who provide transparent engineering, certified foundations, and council-friendly designs.

➡️ Start Here: Compare compliant builders
➡️ Get Online Quotes
➡️ Download the Modular Homes Guide

Related reading:

• Why WaterMark Certification Matters in Prefab Homes
• Heating and Cooling for Tiny, Container and Modular Homes

Sources and References

1. NCC Volume 2, Housing Provisions, ABCB
2. AS 2870:2011, Residential Slabs and Footings
3. AS/NZS 1170, Structural Design Actions
4. Queensland Government, Wind Region Maps
5. NSW Manufactured Homes and Movable Dwellings Regulation 2021
6. Tiny Home Quotes, Expandable Home Approval Guide

Modular Myths & Tiny Truths is our ongoing series dedicated to helping Australians make confident, safe, and compliant decisions in the tiny and modular home market.