Category: Shed Guides

Why Insulate Your Steel Shed?

Steel is an excellent building material — strong, durable, termite-proof, and fire-resistant. But it conducts heat and cold efficiently, which means an uninsulated steel shed can be unbearably hot in summer, freezing in winter, and prone to condensation year-round.

Insulation solves all three problems. For livable shed homes, insulation isn’t optional — it’s a Building Code requirement. But even for workshops, garages, and hobby sheds, insulation makes your space usable 12 months a year.

The Condensation Problem

Condensation is the number one complaint from steel shed owners who skip insulation. When warm, moist air inside the shed hits the cold steel surface, water forms on the underside of the roof. This leads to:

• Dripping onto stored items, tools, and vehicles
• Rust formation on the inside of the steel (from the outside, your COLORBOND® coating is fine)
• Mould and mildew growth
• Damage to hay, grain, and feed in farm sheds

The solution is a vapour barrier combined with insulation — creating a thermal break between the warm inside air and the cold steel.

Insulation Types for Steel Sheds

Reflective Foil (Sisalation / Anticon)

The most common insulation for steel sheds. A layer of reflective foil laminate is laid over the purlins before the roof sheeting is installed. Anticon is the brand name for foil-backed blanket insulation specifically designed for steel roofing.

• R-value: R1.0 to R1.5 (reflective only) or R1.5 to R2.5 (with blanket)
• Best for: garages, workshops, storage sheds — stops condensation and provides basic thermal comfort
• Cost: $8–$15/m² installed

Glasswool Batts

For livable sheds and spaces that need higher thermal performance, glasswool batts are installed between the steel frame and internal lining. This is the standard approach for meeting BCA energy efficiency requirements.

• R-value: R2.0 to R6.0 depending on thickness
• Best for: livable shed homes, offices, studios — meets NCC/BCA energy requirements
• Cost: $15–$30/m² installed (including vapour barrier)

Spray Foam

Closed-cell spray foam provides excellent insulation and acts as its own vapour barrier. It’s applied directly to the inside of the steel cladding.

• R-value: R3.5 to R6.0+ per 50mm thickness
• Best for: cold climates, high-performance builds, odd-shaped spaces
• Cost: $25–$50/m² installed — the most expensive option but the best thermal performance

Which R-Value Do You Need?

The required R-value depends on your climate zone (as defined by the NCC) and whether your shed is habitable:

• Non-habitable sheds — no minimum requirement, but R1.0+ stops condensation
• Climate zones 1–3 (tropical/subtropical QLD, NT, northern WA): walls R2.8, ceiling R4.1 minimum
• Climate zones 4–5 (temperate NSW, VIC, SA): walls R2.8, ceiling R4.1–R5.1
• Climate zones 6–8 (cool/alpine TAS, highlands): walls R2.8–R3.8, ceiling R5.1–R6.3

Your building certifier will confirm the exact requirements for your location.

Installation Tips

• Install roof insulation before sheeting — it’s much easier to lay foil/blanket over the purlins before the roof goes on
• Don’t compress batts — squashing them reduces their R-value significantly
• Seal all gaps — insulation only works if air can’t bypass it. Tape joins in foil, fill gaps around doors and windows
• Ventilate — even insulated sheds need some airflow. Whirlybirds, ridge vents, or louvre vents prevent moisture build-up
• Consider wall insulation too — roof-only insulation helps but walls are responsible for 25–35% of heat transfer

Planning a shed that needs insulation? Design it in our 3D tool and we’ll help you choose the right insulation approach for your climate and use case.

Why Your Shed Foundation Matters

Your foundation is the most critical part of any shed build. Get it wrong and you’ll deal with cracking, shifting, water pooling, and structural problems for the life of the building. Get it right and your shed will perform exactly as engineered for decades.

For steel frame sheds, the foundation must match the engineering specifications. Every Shedz kit comes with site-specific engineering drawings that specify exactly what your slab or footings need to look like — including dimensions, reinforcement, hold-down bolt locations, and concrete strength.

Types of Shed Foundations

Concrete Slab on Ground

The most common foundation for steel sheds in Australia. A reinforced concrete slab provides a level, durable surface that doubles as your floor. Typical specifications:

• Thickness: 100mm for residential sheds, 150mm+ for heavy vehicle or industrial use
• Concrete strength: N25 or N32 depending on engineering requirements
• Reinforcement: SL82 or SL72 mesh, with additional reinforcement at edges and thickenings
• Edge beam: typically 300mm x 300mm with N12 reinforcing bars
• Hold-down bolts: cast into the slab at precise locations matching your frame layout

Important: Always refer to your signed-off engineering drawings for the concrete slab and footings design and specifications for your specific shed. The above are general guidelines only — your engineer’s specifications take priority.

Pier Footings

Pier footings (also called pad footings or post footings) are individual concrete pads poured at each column location. They’re common for:

• Sloping sites where a full slab isn’t practical
• Rural properties where a gravel or earth floor is preferred
• Farm sheds where machinery needs to drive in and out
• Budget-conscious builds where you want to minimise concrete costs

Each pier is typically 600mm x 600mm x 600mm deep, with hold-down bolts cast in. Your engineering drawings will specify the exact size and depth based on your soil classification and wind loads.

Strip Footings

A continuous strip of concrete along the shed walls. Less common for standard sheds but sometimes used for livable shed homes where the wall loads are distributed along the entire length.

Site Preparation

Before any concrete is poured, your site needs to be prepared:

1. Soil test — a geotechnical report classifies your soil (A, S, M, H, E, or P class). This determines your footing design.
2. Clearing and levelling — remove vegetation, topsoil, and level the pad area
3. Compaction — compact the sub-base to the required density
4. Drainage — ensure water drains away from the slab. Consider ag-pipe around the perimeter.
5. Services — if your shed needs water, sewer, or electrical, run the pipes and conduits before the slab is poured

Getting the Hold-Down Bolts Right

This is where most DIY slabs go wrong. Hold-down bolts must be placed at exact positions matching your steel frame layout. Even 10mm out and you’ll have problems bolting down the columns.

Tips for getting it right:

• Use a template or jig — many shed suppliers provide bolt layout drawings
• Double-check dimensions before the pour — measure diagonals to ensure square
• Set bolts to the correct height — too low and the thread won’t engage, too high and the baseplate won’t sit flat
• Protect bolt threads during the pour — wrap with tape or use bolt caps

Cost Guide

Concrete slab costs vary significantly based on site conditions, location, and concrete prices in your area. As a rough guide:

• Small residential shed (6m x 6m): $3,000–$6,000
• Medium shed (12m x 9m): $8,000–$15,000
• Large farm/commercial shed (18m x 12m+): $15,000–$30,000+

These figures include excavation, formwork, reinforcement, concrete supply, and finishing. Add 20–30% for difficult sites (slope, rock, poor access).

Choosing a Concretor

For owner builders, the slab is one job worth getting a professional for. Look for:

• Experience with shed slabs (not just house slabs — the bolt layouts are different)
• Willingness to work from your engineering drawings
• A clear quote that itemises concrete volume, reinforcement, and finishing
• Insurance and licensing appropriate for your state

Need help planning your shed foundation? Contact Shedz and we’ll provide the engineering drawings your concretor needs to get it right first time.