In most situations, yes — a homeowner can remove a prefab concrete garage base themselves using hired equipment, without needing a building consent. However, before you fire up a jackhammer, there are several important checks around safety, utilities, waste disposal, and NZ Building Code obligations that you need to work through first.
Check Whether a Building Consent Is Required
Demolition of a minor structure like a freestanding garage base is generally exempt from building consent under Schedule 1 of the Building Act 2004, provided the garage itself is not attached to your home and is a detached outbuilding. However, exemptions have conditions and your local council has the final say. Always confirm with your local territorial authority (council) before starting work. You can find general guidance on what requires consent at MBIE Building Performance.
If the garage slab is connected to a stormwater drain, wastewater pipe, or any other services, those connections will need to be properly capped or redirected — and that work may involve licensed tradespeople (see below).
Locate Underground Services First — This Is Critical
Before breaking any concrete, you must identify and mark all underground services. Striking a buried electrical cable, gas line, or water pipe is extremely dangerous and potentially fatal.
- Contact Dial Before You Dig (0800 248 344 or dialbeforeyoudig.co.nz) to get utility plans for your property.
- Visually check for any conduit, pipes, or cables entering the slab from the ground.
- If you find services, have them isolated or disconnected by the appropriate licensed professional before proceeding.
WorkSafe NZ has clear guidance on working safely around underground services — it's worth a read before you start.
Restricted Work: Electrical, Gas, and Plumbing
If your garage had power, lighting, or a gas connection, disconnecting these is restricted electrical or gas work and must be carried out by a licensed professional:
- Electrical disconnection must be done by a registered electrician (check EWRB).
- Gas disconnection must be done by a licensed gasfitter (check PGDB).
- Plumbing or drainage connections (e.g. a floor drain) must be capped by a licensed plumber or drainlayer.
Do not attempt to disconnect any of these services yourself — it is illegal and dangerous.
Tools You'll Need to Hire
For a standard prefab concrete garage base (typically 100–150 mm thick), the following hired equipment will make the job manageable:
| Tool | Purpose |
|---|---|
| Electric or petrol jackhammer (demolition hammer) | Breaking up the concrete slab |
| Angle grinder with diamond blade | Cutting control joints or edges |
| Pry bars and bolt cutters | Removing reinforcing mesh or rebar |
| Concrete skip bin or trailer | Disposing of broken concrete |
| Safety PPE (see below) | Protecting yourself throughout |
You can hire this equipment from most tool hire centres at Bunnings or Mitre 10, as well as specialist hire companies. As a rough guide, a full day's jackhammer hire typically costs somewhere in the range of $80–$180 per day, though prices vary by region and supplier — always confirm current rates directly.
Safety Gear Is Non-Negotiable
Concrete demolition is physically demanding and creates real hazards:
- Eye protection (safety glasses or goggles) — flying concrete chips are a serious risk
- Hearing protection — jackhammers are extremely loud
- Dust mask (P2 rated minimum) — concrete dust contains silica, which causes serious lung disease with repeated exposure
- Steel-capped boots
- Heavy-duty gloves
- High-visibility vest if working near a road or driveway
Refer to WorkSafe NZ for further guidance on personal protective equipment and safe work practices.
Breaking Up and Removing the Concrete
Once services are confirmed clear and isolated:
- Score the perimeter with an angle grinder if the slab butts up against a path, fence, or building.
- Start jackhammering from one edge, working inward in manageable sections. Smaller chunks (roughly 30–50 cm) are much easier to handle and load.
- Check for reinforcing mesh or rebar — use bolt cutters or an angle grinder to cut it into manageable lengths.
- Load broken concrete into a skip bin or trailer as you go. Concrete is very heavy — a standard 100 mm slab over a single garage (roughly 6 m × 3 m) can weigh several tonnes.
Tip: Concrete cannot go into your household rubbish or green waste. You'll need to arrange a concrete skip bin or take it to a transfer station that accepts construction and demolition waste. Check with your local council for approved disposal sites.
What to Do with the Sub-Base
Prefab garage bases often sit on a compacted gravel or sand sub-base. Once the concrete is removed, you may need to:
- Re-compact or remove the sub-base depending on your plans for the area.
- Check for any residual oil or chemical contamination if vehicles were stored there — contaminated soil may need specialist disposal.
When to Call a Professional
Consider hiring a qualified demolition contractor if:
- The slab is unusually thick (200 mm+) or heavily reinforced
- The slab is attached to or very close to your home's foundation
- You discover asbestos-containing materials (common in pre-1990 garages — stop work immediately and contact a licensed asbestos removalist)
- Underground services are unclear or complex
- You simply don't have the time, physical capacity, or confidence to do it safely
A local demolition contractor can often remove a standard garage slab in a single day and handle all waste disposal. You can find qualified demolition contractors in your area at tradedirectory.co.nz.
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