Artificial grass installation depends on three things most homeowners never see: what goes under the turf, how much infill sits inside it, and how water moves through the whole system. This guide walks you through each layer, from soil preparation through the finished surface, so you understand what separates a durable installation from one that settles, puddles, smells or fails at the seams. Whether you are converting a moss-covered lawn, building a dog run that stays dry, or preparing a patio for turf, the foundation work determines how long the turf lasts and how well it performs.
The guide is written for Portland homeowners and property managers. Portland's heavy clay soils, long wet season and tree-shaded yards create specific challenges that influence every step of base prep and drainage design. If you are ready to move forward, we offer a free estimate that includes an on-site measurement and a written specification naming every material and depth.
Turf Infill Options: Silica, Coated Sand, Zeolite and Envirofill
Infill is the material spread inside the turf fibres. It serves as ballast to hold the blades upright, protects the backing from UV damage, adds weight for stability, and plays a role in drainage and odor control. The most common infill is silica sand, a fine mineral that is affordable and effective for general residential use. Silica comes in various grades, and the finer grades work well in Portland's climate where drainage is already a concern. Coated sand is silica that has been rounded and sometimes coloured or treated; the coating makes it gentler underfoot and can reduce dust, and some formulations include antimicrobial or odor-reducing properties.
Zeolite is a porous mineral that absorbs moisture and odors, making it popular in pet turf and dog runs where urine smell is a concern. Cooling infills and antimicrobial coated sands sold under brand names such as Envirofill are engineered to reduce surface heat and inhibit bacterial growth; these cost more than basic silica but are worth considering in high-traffic pet areas or commercial applications. Crumb rubber, made from recycled tires, is standard for athletic fields and sports courts where impact absorption matters, but it is not commonly used in residential yards because of cost, heat retention and maintenance demands. Your installer should specify the infill type and amount in writing before work begins.
How Much Infill Artificial Grass Needs, and Why
Infill is measured in pounds per square foot, and this number is critical. Too little infill is one of the most common shortcuts taken by budget installers: the turf may look acceptable at first, but without enough infill the fibres flatten, the backing is exposed to UV and begins to break down, drainage becomes inconsistent, and pet odors concentrate instead of being absorbed and dispersed. Typical residential turf requires between 2 and 4 pounds of infill per square foot, depending on the turf product itself, the pile height, the fibre type and the intended use. A pet turf installation may call for infill at the higher end or a specialized blend. A putting green has its own infill specifications. The installer should provide this figure in writing as part of the spec, not as a verbal estimate or a range.
Infill also supports drainage by creating pathways for water to flow down through the turf and into the base. When infill is too light, the turf compacts unevenly, creating low spots where water pools. When it is absent altogether, the backing can float or shift. Ask any installer you are considering to state the infill amount in pounds per square foot and the type in writing before the work begins. This is one of the details that separates transparent, professional work from installations designed to minimize cost at the expense of performance.
What to Put Under Artificial Grass for Drainage
What lies beneath the turf determines whether water drains away or sits and causes odor, settling and deterioration. The process begins with removal: the existing lawn, dead sod, roots and debris must be cleared away completely. Any old turf being replaced should be removed down to bare soil. Once the area is clear, excavation is the next step. The depth of excavation depends on the existing grade, the slope of the yard, and whether you are working on bare soil, concrete or another hard surface. The goal is to create a level or gently sloping base that will shed water away from structures like the house or pool.
After excavation, a weed barrier (landscape fabric) is laid down in most residential installations to prevent weeds from growing up through the turf. On top of that goes a free-draining base material, typically decomposed granite or crushed base rock, compacted in layers. For patios, balconies, turf-paver strips and hard surfaces, an optional draining underlay or pad sits between the base and the turf to add comfort and improve drainage. The same applies to pet areas where moisture and odor management is important. Never install turf directly on concrete or a slab that does not drain; water will pool beneath it, the backing will rot, and odors will accumulate. If you are working on an existing patio or deck, edge drainage must be designed so water does not collect at the perimeter.
Base Prep on Portland Soil: Excavation, Base Rock and Compaction
Portland soils are predominantly clay and clay-heavy loam, especially in the established neighborhoods of Laurelhurst, Irverson, Sellwood and Hawthorne where many of the city's oldest homes sit. Clay drains slowly and holds water, which means a proper base preparation is not optional. The first step is to excavate the existing lawn or old turf down to subsoil, removing all roots and organic matter. The excavation depth is typically three to four inches, though slopes, drainage problems and the type of base material may require more. Once the area is excavated, the ground is graded to create a gentle fall away from the house, any pool or any structure that should not collect water. This slope is subtle, usually one to two percent, but it is essential.
Next, a base of decomposed granite or crushed base rock is laid down and compacted in lifts, usually two inches at a time, using a plate compactor. Compaction is done firmly but not so aggressively that the soil becomes impermeable; the goal is a stable, level surface that will not settle under foot traffic. An uncompacted base is a false economy: it settles unevenly over months, creating dips and puddles where water collects, infill migrates to low spots, and odor concentrates in pet areas. In yards where clay is deep or where water already pools during the wet season, drainage may need to go further: a French drain, a dry well or a swale that directs water away from the installation. If a yard has a genuine water problem, drainage must be addressed before turf is installed, or the job should be declined. We will discuss this honestly during the estimate.
Artificial Grass Drainage and Underlay: Perforated vs Fully Permeable
Water moves through artificial turf in two ways: through the infill and fibre, and through the backing of the turf itself. Turf backings are either perforated (punched with small holes) or fully permeable (woven or non-woven fabric that allows water through). Perforated backing is common in residential turf and works well when the base underneath is compacted and drains freely. Fully permeable backing offers faster drainage and is preferred in areas with heavy rain, high pet traffic or where puddles are a concern. The drainage rate of a turf backing is measured in gallons per hour per square foot, and a quality installer will know this figure for the product being installed. A fast-draining turf backing, however, cannot overcome a slow-draining base: if water cannot move down through compacted clay or an uncompacted base, it will sit on top of the turf or pool at the edges.
In Portland's wet climate, pet areas and play spaces are where drainage is truly tested. A dog run that receives heavy use and regular rain needs a base that drains quickly and a turf backing that does not slow water down. Underlays and drainage pads designed for hard surfaces (patios, balconies, rooftops) sit between the base and the turf to add a buffer layer and improve water flow. These pads are also valuable in areas where the ground stays damp or where odor control is important. The key is that every layer, from the base rock up through the infill and backing, must work together. A spec should state the drainage rate of the turf backing and confirm that the base has been compacted to support it. If water is pooling or if odor is persistent after installation, the problem usually lies in the base, not the turf.
Seams, Nails, Edging and Power Brooming
The details that separate professional work from a quick installation are visible in the seams, edges and finish. Seams are where two pieces of turf meet, and they must be joined with seam tape and adhesive, with the grain (the direction of the fibres) aligned so the joint is invisible. A visible seam or one where the fibres do not match tells you the installer rushed or did not know the technique. Nails or staples that hold the turf down must be spaced correctly, typically every six to eight inches around the perimeter and at seams, so the turf does not shift or lift. Lifting at the edges is a common failure, especially in areas where foot traffic is heavy or where the sun heats the turf and causes it to expand.
Edging is finished with bender board (flexible plastic or metal edging) or a secured perimeter that prevents the turf from creeping outward and infill from migrating to the sides. Where turf meets pavers, a cool deck or a patio, it should be cut tight to the edge so water drains away and no gaps trap debris or create a tripping hazard. Finally, power brooming is done after installation to stand the fibres up, spread the infill evenly and give the turf a finished, uniform appearance. A turf that looks matted, uneven or has visible seams is a sign that finishing work was skipped or done poorly. These details matter because they affect how the turf looks, drains and holds up over time.
What a Written Turf Spec Should Include
Before any work begins, ask for a written specification that names every material and dimension. A complete spec includes the turf product name and fibre type (polyethylene, polypropylene or nylon), the face weight in ounces per square yard, the pile height in millimetres, the backing type (perforated or permeable) and its drainage rate in gallons per hour per square foot, the infill type and amount in pounds per square foot, the base material and depth (for example, three inches of compacted crushed rock), whether a weed barrier will be installed, the seam method, the edging material and type, cleanup and haul-off, and the workmanship warranty period. This spec is your protection: it proves what was promised and allows you to verify that the work was done correctly. It also gives you something to compare if you are getting multiple estimates.
A homeowner should never accept a price per square foot without an on-site measurement, and should never accept a verbal promise about materials or depth. We provide a free estimate that includes a site visit, a written spec and a pricing breakdown. The spec is the document you keep; it is the proof of what was installed. If you ever need turf repair or have questions about the installation later, the spec tells any future installer exactly what is underneath and what was specified. This transparency is how you protect your investment and hold any installer, including us, accountable.