How Much Does a Concrete Garage Slab Cost in Mandurah?
Quick answer: A concrete garage slab in Mandurah typically costs around $95 to $150 per square metre, supplied and laid, based on published 2026 Western Australian pricing. A standard double garage of about 36 square metres therefore usually costs roughly $3,400 to $5,400 for the slab. Costs rise with site preparation, thickened edges, vapour barriers, removal of old slabs and decorative or sealed finishes.
Garage slabs carry vehicles, tools and storage every day, so the specification matters as much as the price. Most are poured around 100 to 125 millimetres thick with reinforcement mesh on a well-compacted base.
Garage Slab Cost at a Glance
| Garage size | Area | Typical slab cost |
|---|---|---|
| Single garage (3 m × 6 m) | 18 m² | $1,710 to $2,700 |
| Large single (3.6 m × 6 m) | 21.6 m² | $2,050 to $3,240 |
| Double garage (6 m × 6 m) | 36 m² | $3,420 to $5,400 |
| Large double (6.5 m × 7 m) | 45.5 m² | $4,320 to $6,825 |
| Triple garage or workshop | 54 m² | $5,130 to $8,100 |
Extras such as demolition of an old slab (roughly $45 to $120 per square metre), extra excavation, drainage or sealing add to these figures. Always request itemised written quotes.
What Is Included in a Garage Slab?
A proper concrete garage slab involves more than pouring concrete. A thorough quote should include:
- Site preparation. Excavation, levelling and removal of vegetation or old surfaces.
- Compacted base. Crushed rock or limestone, compacted in layers.
- Vapour barrier or damp-proof membrane. Often required under slabs for buildings.
- Formwork and edge beams. Boxing to hold the concrete and thickened edges where needed.
- Reinforcement. Mesh and bar chairs, with additional steel in edge beams.
- Concrete supply and placement. The correct strength and thickness.
- Finishing. Often a trowel or light broom finish, depending on use.
- Control joints and curing. To manage cracking and strength gain.
- Cleaning up and disposal of waste.
Recommended Garage Slab Specification
| Feature | Typical specification |
|---|---|
| Thickness | 100 to 125 mm |
| Reinforcement | SL72 or SL82 mesh |
| Concrete strength | 25 MPa, sometimes 32 MPa |
| Base | About 100 mm compacted crushed rock or limestone |
| Membrane | Plastic vapour barrier under the slab |
| Edge beams | Thickened edges about 300 mm deep around the perimeter |
| Fall | Slight fall toward the door or drain, if required |
| Joints | Control joints to guide cracking |
Heavier vehicles, workshops, car hoists and storage racks may require thicker slabs and extra steel. If the garage is attached to a house, the slab is often part of the house footing design and must meet the engineer’s specification.
Attached Garage vs Freestanding Garage
Attached garage. Usually poured with the house slab or as part of the building contract. The engineer’s design and the concrete foundations cover thickness, steel, edge beams and connection to the house. Floor levels must align with the house, with a step down where required.
Freestanding garage. An independent slab with its own footings and edge beams. This gives more flexibility in size and finish, but you need to plan drainage, services and approvals.
Always confirm which type you are building, because it changes who designs the slab and how it is priced.
Factors That Affect Garage Slab Cost in Mandurah
Size
Larger slabs cost more overall but usually less per square metre.
Thickness and Reinforcement
Thicker slabs, heavier mesh and edge beams add concrete and steel costs.
Site Conditions
Sandy soils drain well but must be compacted. Sloping sites, fill, tree roots or poor drainage increase excavation and preparation time.
Access
Narrow side access, fences and limited truck access may require pumping or extra labour.
Existing Structures
Demolishing and removing an old garage slab, shed or paving adds cost.
Finish
A standard trowel or light broom finish is the most economical. Sealed, coloured, polished or epoxy-coated finishes cost more.
Services
Floor drains, conduits for power, water or compressed air should be installed before the pour.
Approvals and Inspections
Building permits, engineering design and inspections add to total project cost.
Finishes for Garage Floors
Light Broom or Float Finish
A practical finish that gives traction for vehicles and foot traffic. It is the most common garage option.
Smooth Trowel Finish
A smoother surface that is easier to sweep, but it can be slippery when wet. It suits indoor garages that stay dry.
Sealed Concrete
A penetrating or film-forming sealer protects against oil, fuel, brake fluid and stains.
Epoxy or Polyurethane Coatings
Durable coatings add colour, gloss and chemical resistance. They need proper surface preparation and curing time before application.
Polished Concrete
Polished concrete is a hard-wearing, low-maintenance option with a modern appearance, though costs are higher.
Garage Floors and Vehicle Loads
Ask your concreter about:
- Vehicle weight. Utes, 4WDs and caravans place greater loads on slabs.
- Point loads. Car hoists, jacks, workbenches and racking concentrate weight.
- Turning loads. Tight turning areas may need extra strength.
- Future use. If you might add a workshop or heavy equipment, plan for it now.
Upgrading slab thickness or steel during the original pour is far cheaper than repairing cracks later.
Moisture, Vapour Barriers and Damp Protection
Concrete is porous, so moisture can move up from the ground. In many buildings, a plastic membrane under the slab helps reduce moisture transfer. This is important if you plan to:
- Store sensitive items such as paper, textiles or electronics.
- Apply coatings or epoxy to the floor.
- Convert the garage to living space in the future.
Your concreter or builder should confirm what membrane and detailing are required for your site and project.
Drainage and Floor Levels
Good levels keep the garage dry and safe.
- Slight fall toward the door helps water run out of the garage.
- Floor drains can be added if you wash vehicles or expect water.
- Set levels above surrounding ground to prevent water entry, with proper drainage outside.
- Connect to approved stormwater where required.
- Check thresholds at door openings and transitions.
Garage Slab Approvals in Western Australia
Garages commonly need building and planning approval, especially for new or enlarged structures. Rules cover matters such as size, height, setbacks from boundaries, materials and use. Freestanding garages and sheds have their own requirements, and some small structures may be treated differently from larger ones.
Because requirements vary by property and project, check the current rules with the City of Mandurah and your builder before you start. Make sure inspections, such as footing inspections before the pour, are booked at the right time.
Local Considerations in Mandurah
Sandy soils. Strong compaction and proper base preparation are essential to avoid settlement and cracking.
Coastal conditions. Salt air can affect steel and surfaces, so appropriate concrete quality and cover are important.
Summer heat. Hot weather requires early starts, curing and joint cutting at the right time.
Winter rain. Drainage and protection from water during construction are critical.
Site classification. Engineers design slabs based on soil classification, so a soil test may be required.
How to Save Money on a Garage Slab
- Pour with the house or other concrete slabs to reduce setup costs.
- Keep the design simple. Standard rectangles are easiest and cheapest.
- Choose a standard finish and add a sealer or coating later if needed.
- Plan services early, including drains and conduits.
- Avoid under-spec. A thin or poorly prepared slab can crack and cost more to fix.
- Compare itemised quotes to see what is included.
Questions to Ask Your Concreter
- What thickness, mesh and strength do you recommend for my vehicles and use?
- Will the slab include edge beams and a vapour barrier?
- How will the base be prepared and compacted?
- What finish do you recommend for a garage?
- Who arranges engineering and inspections?
- How long before I can park vehicles on the slab?
- What warranty do you offer?
Caring for a Garage Slab
- Keep vehicles off for about a week, and heavy loads off until the concrete has gained strength.
- Clean oil and fuel spills quickly.
- Seal the surface if you want stain protection.
- Use pads under jacks and stands.
- Avoid dragging heavy objects.
- Fill small cracks early and monitor for movement.
Frequently Asked Questions
How much does a garage slab cost per square metre?
In Western Australia, a shed or garage slab commonly costs about $95 to $150 per square metre supplied and laid, depending on site and specification.
How thick should a garage slab be?
Typically 100 to 125 millimetres with SL72 or SL82 mesh, with thickened edges. Heavier use may require more.
Do I need a vapour barrier under a garage slab?
A plastic membrane is commonly used under slabs and is often required. Confirm requirements with your builder or engineer.
Do I need council approval for a garage slab?
Garages usually need building approval, and freestanding structures have their own rules. Check with the City of Mandurah before starting.
How long does a garage slab take to cure?
You can often walk on it after one to two days, drive light vehicles after about seven days and reach design strength after about 28 days.
Can I park a caravan or boat in the garage?
Usually yes, but heavy loads and trailer jockey wheels need adequate thickness and steel. Tell your concreter in advance.
Is epoxy flooring worth it in a garage?
Many people like epoxy for appearance and stain resistance, but surface preparation and moisture control are critical for good results.
Can I extend an existing garage slab?
It is possible, but joining new concrete to old requires careful detailing to avoid cracking and level differences. The same care applies when matching a concrete shed slab to an existing structure.
Final Thoughts
A concrete garage slab in Mandurah typically costs around $95 to $150 per square metre, so a double garage often falls between $3,400 and $5,400 for the slab alone. The right thickness, steel, base preparation, moisture protection and finish matter more than the cheapest quote.
Plan your garage use, confirm approvals, ask for itemised quotes and choose an experienced local concreter. A properly built slab will stay level, dry and durable for decades.