Sales Enquiries | +61 2 9828 2660

Sales Enquiries | +61 2 9828 2660


Planter Box Tips

Drainage & Soil

The importance of effective drainage in planters

Effective drainage is critical for all landscaping activity, not just the planter but also for the plant. A healthy root system ensures plants thrive in their environment, so water needs to drain freely and sufficient air in the soil is needed.  Whilst the soil on the surface may appear dry, the soil at the bottom may be saturated and this excessive water will place pressure on the planter and can cause cracking (in addition to root rot).

Mascot GRC Planters come without drainage holes and rely on installers placing drainage on site. Due to the nature of the material, drainage holes can be made simply on site with a handheld drill in any location and size. The planters are supplied without drainage holes to give installers the ultimate in flexibility to place them in a location that suits the installation. We recommend holes be a minimum of 25mm in diameter (multiple per planter) and that they be placed more than 100mm from the sides or ends.

Once drainage holes are made, they should be covered with a thin layer of geofabric filter wrap to prevent blocking – whilst still allowing water egress.  Failure to provide adequate drainage may void the product warranty. For larger planters we recommend the installation of a drainage cell covered with the geofabric – please refer to manufactures installation details.

The use of automated irrigation should be considered carefully and adjusted regularly at first to ensure adequate time for the plants root to take in the water.

Planting & Potting

There are a range of premium mixes (podium mix) and soils on the market that have been developed specifically for planters/containers. These soils are lightened to facilitate drainage and are great for your plants and planters.  Plants selected should be chosen bearing in mind current and future root systems and species requirements based on the planter capacity.

NOTE: Clay, sand or top soil should not be used as a substitute to podium potting mix… these materials can be too dense and cause drainage issues which not only effect the planters but the plants also.  Use of these materials void any warranty on our product.

Finish & Paint Application

All Mascot Engineering planters are supplied in a raw Glass Reinforced Concrete (GRC) state with no applied finishes. GRC is a concrete product – air holes and imperfections are common. Paints and waterproofing sealants can be applied, we recommend only using products that are suitable for concrete or masonry in an outdoor environment. For longer lasting finish, ensure the product is clean, an appropriate undercoat is applied as well as a waterproof coating internally.

Levelling and Placement

Even weight distribution is key for planters due to the weight of the contents. Uneven ground contact may cause stress cracks in the planters, therefore it’s imperative that the planter should not rock at all once placed and appropriate action should be taken when installing to ensure the base is evenly supported. Failure to install on a level surface will void the product warranty.

Inground Installation

Mascot Engineering GRC Planters can be installed in ground if required.  The external of the planter should be coated in a liquid membrane in addition to drainage holes and at least a 50mm sand bed beneath the planter for drainage.  Specialist advice will be required if installing in clay soils.

Suspended Slabs

Positioning planters on a suspended slab should be considered with professional advice as all structures are subject to short- and long-term deflection. Planters can’t be positioned over expansion joints and there must be a gap between any two planters.  The size of the gap will differ from project to project and professional advice on your project should be sought. This advice should consider the type of structure and size of span… coordinating the construction tolerance and slab deflection. Whether a structure is reinforced concrete or prestressed concrete, all are designed with an allowance for deflection, and this should be considered when designing and installing planters. From what we’ve experienced, a gap of no less than 20mm between the planters is common, though all builds vary.  AS3958 covers ceramic tiles, however it makes specific reference to the need for expansion joints in tiling which is transferable to planters.

Pedestrian Balustrade

Mascot Engineering GRC Planters are commonly used on the perimeter of buildings in place of a balustrade or railing.  The use of planters in this manner should be subject to a strict structural engineering review and assessment of your project.


In addition to the warranty details in our standard trading terms, Mascot Engineering Planters warranty covers against structural defects. Fading and hairline cracks are common in masonry products and are not covered under this warranty. Glass Reinforced Concrete surface finishes can vary in look and colour slightly and any tone irregularities are not covered under warranty.


Mascot Engineering GRC Planters require minimal maintenance. A wet cloth and mild cleaning product can be used to clean the external surfaces if required, however please refrain from using abrasive products.


Mascot Engineering Planters are supplied on timber pallets. In most instances Mascot Engineering Planters are delivered by one of our trucks equipped with a suitable crane for unloading. Our trucks are large and unloading is to curb side only – we do not install or place planters on site.  For some areas a third party freight carrier may be used in which case a forklift or similar will be required to unload at the delivery point. Unloading like this is to be arranged by the receiver. We will nominate on our quotations the type of delivery that has been allowed and our team will work with you to ensure a smooth and simple delivery that is appropriate to your site.

Please refer to Mascot Engineering trading terms for more information, noting that all planter boxes are considered a ‘Special Order’.

All advice here is general information and does not take into account the particular circumstances of every job, project, site or installation.  Mascot product should always be installed by appropriately licenced professionals who apply their own training and expertise in the context of the particular circumstances to which they’re being used.  Please refer to Mascot Engineering Trading Terms and Conditions which can found at