Base Preparation: The Part of the Installation Nobody Photographs

Every synthetic lawn failure we hear about traces back to the same place. Not the turf, which is a manufactured product with predictable properties, but the ground underneath it. Seams that open, surfaces that ripple, water that ponds, edges that curl — nearly all of it is base failure showing itself six months to three years after installation.

Here is what a correctly built base involves, so you can recognise whether a quote includes one.

Step one: excavation

The existing turf and topsoil come out. This is not optional. Organic material left in place will continue to decompose, and as it does the ground beneath the new surface subsides unevenly. Typical excavation depth is 100–150mm for residential work, deeper where the base needs to carry vehicle or heavy equipment loads. Excavated material has to be carted away, which is a real cost line and a common place for cheap quotes to quietly disappear.

Step two: falls and drainage

Before any aggregate goes in, the sub-grade is shaped to fall towards a defined outlet — a soakage pit, a channel drain, an existing stormwater connection or a garden bed with capacity to absorb the flow. In heavy clay, a perforated drainage coil bedded in scoria under the base is often specified. The critical question to ask any installer is simple: where does the water go? A vague answer is a warning.

Step three: the aggregate base

Compacted aggregate — typically a graded basecourse over a coarser drainage layer — is laid in lifts and compacted with a plate compactor or roller between each lift. Compacting the full depth in one pass does not work; the bottom stays loose and settles later. A finer bedding layer, often crusher dust or a sand-and-lime mix, is screeded on top and compacted to give a flat, firm surface for the turf to sit on.

Step four: laying, seaming and fixing

Turf rolls are laid with the pile direction consistent across every piece — get this wrong and the seams show as colour changes in raking light. Rolls are left to relax and acclimatise before cutting. Seams are joined on tape with adhesive, edges are trimmed and mechanically fixed to a timber, composite or steel perimeter, and infill is brushed in to weight the surface and support the fibres upright.

What good looks like in a quote

A quote for synthetic grass nz homeowners can rely on will state excavation depth, aggregate type and depth, compaction method, drainage outlet, edge fixing method and infill type. A quote that says "supply and install turf, $X per square metre" is not comparable to that, however attractive the number looks.

The base is invisible once the job is done. It is also the entire difference between a surface that lasts fifteen years and one that needs relaying in four.