Often when we go out to inspect a reported Leaking Balcony – we find it is actually the Planter Box that is leaking. Built-In planter boxes, if not waterproofed correctly can deteriorate over time and begin to leak.

When waterproofing a planter box it must be in accordance with AS4654.2-2012 Waterproofing membrane systems for exterior use – Above ground level – Design and installation, Clause 2.7 Planter Boxes.

How to waterproof a planter box

1. Clean and Inspect Planter Box

First you must remove all plants and bag up all soil from the planter box. Wash out the planter box (being careful not to flood) and allow to dry.

Inspect your planter box for any defects and repair any visible cracks, making the surface of the base and sides sturdy and robust. Ensure the base of the planter box is graded with falls to the drainage outlet – a screed may be required to correct levels.

2. Apply Waterproof Seals

Apply waterproof polyurethane seals to the main junction joints of the planter box to seal up all the joints for continuous membrane application. Apply waterproof bandage over any polyurethane seals.

If required, install a drainage outlet/puddle flange into the drain, ensuring it is recessed into substrate.

3. Apply Waterproof Membrane

Apply two coats of waterproof membrane to the planter boxes. Between coats of membrane, apply waterproof bandage the main junction joints 80-100mm up the risers.

The membrane must be sealed and terminate into the drainage outlet/puddle flange, and extend a minimum of 100mm above the expected soil fill level where the planter box abuts a wall.

4. Waterproof Exposed Walls

If the external exposed walls of the planter boxes have not been rendered, these can be waterproofed as a secondary measure to prevent failure of the internal planter box membrane. This should then be rendered. Once fully cured, reinstall all the existing bagged soil in to the planter box.

SCR does not recommend waterproofing Planter Boxes as a DIY project, as if done incorrectly it can cause costly water damage to your property.

At the first sign of a leak – you should contact SCR Melbourne for an expert diagnosis and no-obligation quote for repairs! Click here.