Waterproofing a balcony

Everything You Need to Know About Waterproofing a Balcony: The Ins and Outs

Balcony waterproofing is required to protect any area underneath the balcony from persistent water ingress.


For areas vulnerable to snow or heavy flooding, the waterproofing of balcony surfaces is an integral part of the building process, and cannot be taken lightly. Nobody wants to deal with a leaking balcony down the track!

Keeping a balcony safe from water

An array of different methods can be undertaken to keep your balcony safe from water, utilising new technologies and materials. Balcony surfaces are made using concrete or timber roof, with a layer of waterproofed material that covers and guard the substance.

Please note concrete structures face different issues than timber or steel construction; materials for one may not suit the other. If you haven’t used an appropriate system, or if the waterproofing was performed in a poor way, you could face the problem of repairing your balcony surface repeatedly.

Accumulation of calcium crystals and salts that disfigure the top edges or underside of masonry is known as “Efflorescence”. This cannot form in the absence of water. Chosen materials should have the correct amount of expansion capabilities to match the structural material. They must be able to adhere, thereby creating a good bond and seal.

Correct sequence of works

Penetrative work and fixing down must be performed prior to water sealing and waterproofing. If erecting a balustrade in these areas, baluster posts that fix down to the structural element of the building will probably be required.

In such cases, the sealant or balcony waterproofing material must be able to seal around them, and remain bonded to the steel of the balustrade posts. Choosing a brittle substance is not recommended. The steel will expand more than the substance, and a leak could arise.

Polyurethane based sealants like Sikaflex-11 FC are particularly good for this type of sealing i.e. between different materials. They have extraordinarily strong bonding capabilities, being able to bond to dissimilar materials like stone, steel, glass, rubber etc. They also have a very low and high temperature resistance, and are UV resistant, recommended for areas exposed to sunlight.

When fixing any material to a finished roof, one needs to be very conscious of water ingress, and must seal properly with the correct materials.

Balcony waterproofing tactics

You might embrace several methods of waterproofing balcony surfaces, such as using a waterproof membrane both below and above the screed, or possibly sealing the exterior of the tiles and grout joints.

Quality waterproofing from the outset is key. Leaking balcony repairs are a hassle nobody needs. Be sure you apply the following tactics to ensure good balcony sealing, thus avoiding water ingress:

  • Complete all penetrating works PRIOR to applying waterproofing.
  • Choose a sealant or membrane material that suits your balcony structure, balustrade materials, and roof materials.
  • Ensure any penetrating materials are applied with an additional sealant that will provide an extra seal.
  • Double-check you have a good drainage plan worked out with the balcony levels, so water pools aren’t created.

Waterproofing is important! The process requires just as much attention to detail as tiling or grouting.

AllSealedWA can complete a range of waterproofing solutions tailored to individual projects. This includes specific waterproofing membranes ideal for showers, bathrooms, and balconies, as well as membranes suitable for exposed use on rooftops or terraces.

Give us a call on (08) 6007 3164. A friendly and professional AllSealedWA team member will work with you to find a suitable time for your obligation free consultation.