Choosing Materials and Products for Artificial Grass Installations

It is essential to commence assessing any artificial grass installation by selecting the type of grass matting. Until the product has been chosen, and agreed in writing with the customer, including fully specifying the brand name, product name and full description, it is not advisable to begin to choose the range of materials that will be required to instal the grass.

With such a wide range of specifications in pile depth and density, until a choice has been agreed, the ‘package’ of auxiliary materials cannot be defined.

Artificial Grass Matting

With a pile depth range varying between 12mm and 50mm, the weight factor and method of securing the matting to the ground, it is obviously crucial to understand the need to have the full acceptance of the client before embarking on arriving at a price for the project. For this reason, it is not recommended that a ‘menu’ of rates for installation is produced, as every site will be different. Looking at the various styles and types of grass matting available, every part of a project will revolve around the selection.

Manufactured in a range of different colours and shades of green, with many versions containing a ‘thatch’ of brown ‘stalks’ to replicate real grass, the majority of products are manufactured using polyethylene and polypropylene, the width of the rolls varies between two metres and five metres, with most suppliers offering the full range of sizes.

The depth of pile required will depend on the intended use, with 12 or 15mm usually used for golf or sports, and is not generally used as a ‘lawn’ in a domestic garden. With a maximum ‘standard’ depth of 50mm, the weight and density of pile, plus stitch rate and yarn style, all combine to the bespoke nature of an installation.

Dtex, or Decitex is a metric unit, mainly used for continuous filament yarn, denoted as the mass per gram. The higher the dtex number, the greater the mass, for increased wear resistance, standing ability and denser tactile properties.

Stitch Rate indicates the density of the pile, the higher the number per stitches per square metre, the denser the pile.

Yarn Style of monofilaments in the material indicate the composition of the matting. These monofilaments are used in both the pile ‘stalks’ and also the ‘thatch’ component of the material. The shape of the yarn is designed to allow the ‘stalks’ to return to their shape without deforming under use.

Weight The greater the weight of a matting, compared with the height of the pile is an indicator or both density and quality.

Backing Material is usually polyethylene and polypropylene surrounding a netting, with holes or perforations every 30cm or more to allow water to percolate through the matting.

Ultra Violet Protection The majority of artificial grass matting has a ten-year warranty against fading by ultra-violet light.

It is recommended that samples are provided to the customer before making a selection, noting full specification and product name and manufacturer. This information should be checked against all future documentation including delivery notes, product labels and invoices to ensure full compliance with the product ordered. This is essential to prevent any questions regarding the material supplied and laid, as the product, once installed, may not appear to accord with the sample shown the client.

MOT Type 1 is used as the base material for all AG installations. Produced from crushed limestone, 40mm to dust, to provide a stable sub-base for road surfaces and pathways. It should be laid to a depth of not less than 75mm, preferably 100mm compacted to at least 85mm with a heavy-duty compactor plate or vibrating roller. Applied in two equal layers, each compacted to ensure as firm a base as possible.

MOT Type 3 is a more permeable material made from pure crushed granite, basalt or limestone. Similar in appearance to MOT Type 1, it is technically very different. It is fully certified by The Highways Works, where reduced fines are required for building permeable sub-bases. It is particularly useful as a sub-base under artificial grass installations where large dogs are present, as it helps to reduce problems with urine odours, or where Sustainable Drainage Systems (SuDS) are required. (Dependent on the pile or make-up of the chosen matting, if large dogs are present, a laying base of 3 – 6 mm aggregate may be used as the final layer) (See notes in Chapter Five – Installation Guide and Specification)

Grano-dust is a gritty aggregate, typically 6mm to fines, manufactured from either limestone or granite. It is extremely hardwearing, and compacts in a stable manner once laid. It is laid directly over the MOT sub-base to a depth of between 15 – 20mm and compacted with a heavy-duty compactor plate.

(Alternatively, sharp sand may be used as the final laying bed, although this is not recommended for several reasons. AG matting is porous, and sharp sand may become mobile under the matting, especially when wet, as the particles shift and percolate into the base material. Sharp sand will retain pet urine smells, and attract ants. The cost of sharp sand is lower than grano-dust, which is the only attraction).

Geotextile Membranes. Use a non-woven, geosynthetic product as a base layer UNDER the MOT Type 1 sub-base to prevent the material from sinking in the softer ground underneath. It should also be used as a final matting UNDER the AG matting to prevent weed seeds from penetrating through the perforations in the base. They act as a ground stabiliser and are fully free-drainable materials.

Timber – It is essential to fix the AG matting securely into position. This may be done using timber (Class 4) laid to the outer edge of the lawn, recommended 50mm x 75mm or 50mm x 100mm laid on edge and secured with vertical 50mm x 50mm x 450mm Class 4 wooden pegs and screwed into position. Timber edging may also take the form of 100mm strips of 20mm marine plywood sawn from a 2.4m sheet and curved to suit any bends or wavy edges in the lawn design. These 20mm strips should be laid in a double row to provide a strong edge for the screws to fix into, pegged into position to prevent movement.

Concrete – as an alternative to timber edging, especially on curved designs. Using two strips of 20mm shuttering plywood, pegged into position for strength during curing time, construct twin ‘tracks’ of plywood, 200mm apart @ 100mm high/deep, laid to levels and falls. Infill the timber tracks with wet mix cement and sandy ballast, one part cement to four parts of aggregate, with a twin, overlapping, pair of 10mm reinforcing bars to construct a concrete ‘rail’ or outer edge to the lawn, laid level across the face, and to running levels. (Once cured, remove the timber edges)

Composite products – as an alternative to using timber as an edge, consider using a composite ‘timber’, consisting of wood fibres and recycled plastic, engineered to be a long-lasting alternative to timber. Fix in the same manner as timber edging. Composite edging for curves is usually 50mm wide x 75mm deep, and may be heat treated by an electrical heat-gun gently applied to suit the lines. Secured by vertical pegs and screwed into position.

Adhesive products including flexible UV resistant compounds to fix the matting to concrete bases, or to glue two sheets of matting together and form a join. Some products will require a sealant to be applied first (on concrete edging) whilst others are single component. Use only those adhesives that are recommended for use with AG matting, avoiding solvent-based products.

Jointing Tapes Some joining tapes are self-adhesive, whilst others are non-adhesive seaming tapes, requiring an application of adhesive to joint two surfaces together.

Some require dry working conditions, whilst others may be used in wet weather, with the bonds fully resistant to climatic conditions. Ensure that the choice of products and materials are suitable, and recommended by the manufacturer of the chosen AG matting, selected to suit the site, matting and weather/climate conditions.

Staples. Some installers prefer to use metal staples – essentially square topped pins which are inserted into the grass matting instead of using adhesive products. These pins have two equal length legs, 150mm long, and are gently hammered into position to hold the grass together where joined, or secured at the edges instead of using either timber, composite or concrete edging methods.

Artificial Grass Edging Kits. These are available in place of timber, concrete of composite materials to edge lawns. Some forms are easily bent to go around trees and shrubs, used where stronger forms are unsuitable due to the construction process. Made from high density polyethylene (HDPE), steel or aluminium, these edging products may be included in an installer’s toolkit for certain projects.

Kiln Dried Sand may be used to weight down the edges in some installations, or to bulk up the pile of certain grades of AG matting where the ‘stalks’ require support due to weak density. Often shown as requiring two kilos per square metre to be effective, caution should be taken where clients have pets, as the dust can cause problems with eyes, or a fine powder residue may be carried indoors and damage flooring covers by scouring action by shoes.