Porcelain pavers can be laid directly onto a compacted gravel base — but only when the sub-base is correctly prepared and the right installation method is used. Cut corners on the groundwork and you'll end up with cracked, sunken, or rocking pavers. Here's what you need to know before you start.
Why the Base Matters So Much
Porcelain is a dense, low-absorption material that looks great but is unforgiving of movement. Unlike concrete pavers, porcelain has very little flex. Any settlement or unevenness in the base will telegraph straight through to the surface, causing cracking or lippage (one paver sitting higher than its neighbour). A well-compacted, well-drained gravel sub-base is the foundation everything else depends on.
BRANZ research consistently highlights that poor sub-base preparation is the leading cause of paving failures in NZ residential projects.
What Type of Gravel Base Do You Need?
Not all gravel is equal. For porcelain pavers, you need a two-layer system:
- Sub-base layer: 100–150 mm of compacted AP65 (aggregate passing 65 mm) or similar crushed rock. This provides structural support and allows drainage.
- Bedding layer: 25–50 mm of compacted AP20 (fine crushed rock or chip) screeded to a smooth, even surface.
Avoid using sand as your sole bedding layer under porcelain — it can wash out or shift, especially in wetter NZ climates. If you do use a sand-based bedding, a coarse, angular grit (not beach sand) is preferable, and many tilers recommend a dry-mix mortar bed (4:1 sand to cement) for better stability.
Drainage and Slope: Critical in NZ Conditions
New Zealand's rainfall — particularly in regions like Auckland, Wellington, and the West Coast — means drainage is non-negotiable. Your paved area must fall away from the house at a minimum 1:100 gradient (1 cm drop per metre) to comply with the NZ Building Code's requirements around surface water management (refer to Clause E1: Surface Water).
Check with MBIE Building Performance if your project involves altering ground levels near the house foundation, as this may affect drainage compliance.
Step-by-Step: Laying Porcelain Pavers on Gravel
1. Excavate and Prepare
Dig out the area to a depth of at least 200 mm (more on soft or clay-heavy soils). Remove all topsoil and organic material — these will rot and cause settlement.
2. Compact the Sub-base
Spread and compact your AP65 in 100 mm layers using a plate compactor (available for hire from most tool hire shops). Don't skip compaction — hand tamping is not sufficient for a stable base.
3. Add and Screed the Bedding Layer
Spread 25–50 mm of AP20 or dry-mix mortar over the compacted sub-base. Use screed rails to achieve a flat, graded surface.
4. Lay the Pavers
Lay pavers with a 3–5 mm joint gap to allow for drainage and minor movement. Use plastic spacers to keep joints consistent. Do not butt pavers tightly together — this causes edge chipping and prevents drainage.
5. Check for Level and Lippage
Use a long spirit level or straight edge constantly. Porcelain pavers over 600 mm × 600 mm are particularly prone to lippage if the bed isn't perfectly flat.
6. Fill the Joints
Use a polymeric jointing sand or a fine gravel/grit. Avoid standard builder's sand, which can wash out. Sweep the jointing material in and compact lightly.
Pedestal Systems: A Great Alternative
For decks, balconies, or areas where you need precise levelling, consider a pedestal system. Adjustable plastic pedestals sit on a firm base (concrete or compacted gravel) and support each paver corner, allowing for drainage underneath and easy levelling. Products are available from tile suppliers and some Bunnings and Mitre 10 stores.
Pedestal systems are especially useful on sloped sites or where you want to run services (irrigation, drainage) beneath the paving.
Paver Thickness Matters
For a gravel-set installation, use pavers that are at least 20 mm thick. Thinner porcelain tiles (10–12 mm) are designed for mortar or adhesive installation onto concrete — they will crack under point loads on a gravel bed.
| Paver Thickness | Suitable for Gravel Base? | Notes |
|---|---|---|
| 10–12 mm | No | Mortar/adhesive to concrete only |
| 18–20 mm | Yes (with care) | Minimum for gravel set |
| 20–30 mm | Yes | Recommended for foot traffic |
| 30 mm+ | Yes | Best for driveways or heavy use |
Do You Need a Building Consent?
In most cases, laying garden pavers is exempt from building consent under Schedule 1 of the Building Act 2004. However, if the work involves retaining walls over a certain height, changes to drainage affecting neighbouring properties, or structures attached to the house, consent may be required. Always confirm with your local council before starting.
When to Call a Professional
While a competent DIYer can tackle a straightforward patio, consider hiring a qualified tiler or landscaper if:
- The area is large (over 20–30 m²) or complex in shape
- The ground is soft, clay-heavy, or poorly drained
- The paving is adjacent to the house foundation
- You're working on a slope requiring retaining or significant cut-and-fill
- You want a warranty on the workmanship
A professional tiler will have access to the right compaction equipment, know how to read site drainage, and can advise on the best bedding system for your specific soil conditions. You can find qualified local tilers on tradedirectory.co.nz.
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