Leaking roof deck or balcony? How to choose the right waterproofing product and end the puddles for good

Every rainy season, what homeowners fear most is a leaking roof deck or balcony that leaves water stains, black mould or drips from the ceiling. Leaving it not only causes frustration but also damages the concrete and reinforcing steel over the long term. Choosing the right waterproofing product is the key to solving this for good.

How to choose waterproofing for each area

There are many types of waterproofing on the market, each clearly suited to different jobs:

• Acrylic waterproofing: suits roof decks or balconies with a good slope and no standing water; moderately flexible, good UV resistance, easy to use and easy to recoat yourself
• Polyurethane (PU) waterproofing: the popular choice for exterior roof decks; very flexible (bridges cracks well) and excellent at withstanding standing water and impact; suits areas exposed to heavy sun and rain
• Flexible cementitious waterproofing: ideal for balconies before tiling over them, or for very damp areas, because it bonds excellently to concrete and gives strong adhesion

A 4-step checklist for waterproofing that lasts and doesn't peel

1. Clean the surface: wash off all dirt, algae and dust, and always let the surface dry completely before starting

2. Repair cracks: if cracks are wider than 1-2 mm, fill them with polyurethane sealant (PU sealant) and finish the edges of all joints neatly

3. Apply the first coat with fibre mesh: apply the first coat of waterproofing, then lay fibre mesh over joints, corners or cracks for extra strength

4. Apply the second coat: once the first coat has dried for the specified time, apply the second coat in the crossing direction (e.g. first coat vertical, second horizontal) for complete coverage

Important caution: If the roof deck or balcony has large cracks, spalling concrete, a sagging structure, or visible rusting reinforcement, these are directly about the structural safety of the house and shouldn't be fixed by applying waterproofing yourself. Call a specialist or engineer to inspect and repair the structure first.

That's all it takes to choose the right waterproofing for the job and keep your roof deck or balcony dry and free from leaks for years.