Hello, we need to waterproof our 24 sqm balcony. There are few cracks and water leaks through into the garage. We received a quote from a very well established business which is more than $14K. So planned to do it DIY but need real experts suggestions as we are in Tassie and the sun is very strong here and we don't have any plan to tile it after waterproofing. So wondering, what kind of membrane we need to use for moderate foot traffic. What I found after researching online is mainly 3 steps, clean, crack repair and then finally waterproofing (2 coats). And Sika 488 or Ardex WPM 157 Polyurethane Membrane are the recommended products. Any suggestion with the steps and materials will be really helpful. Cheers
Hello @arefinforbd
Thank you for sharing your question about waterproofing your balcony. You’re definitely on the right track and your proposed prep method is solid. For a balcony that will remain exposed and take moderate foot traffic, a polyurethane trafficable membrane is the correct choice, and using Sika Sikalastic-488 Polyurethane Waterproofing Membrane (special order) is a good call. It’s designed for exposed balconies and forms a seamless flexible waterproof layer that handles UV, light movement and regular foot traffic when applied at the correct thickness.
Start by giving the balcony a very thorough clean using 30 Seconds Outdoor Cleaner together with a stiff scrub brush, then rinse well with a power washer and allow it to dry completely. The goal here is removing mould, dirt, chalky concrete and any contaminants because membranes bond mechanically to the surface and anything left behind can cause failure later. After cleaning, open up any cracks slightly, if possible, then fill them using Earl's 500g Concremate Expanding Cement which expands slightly as it cures and helps lock into the crack rather than shrinking away. Once patched, allow it to fully cure and lightly sand or grind any high spots so the surface is smooth and even.
Before applying the membrane, it’s very important to prime the concrete, particularly if it’s porous which most balcony slabs are. A compatible primer for this system is Sika Sikalastic-100 EP Primer (special order), which is designed to be used under Sikalastic polyurethane membranes and helps seal the surface, improve adhesion and reduce pinholes. Apply the primer in a thin even coat and allow it to become tack-free before applying the membrane. Very porous or dusty concrete may benefit from a second light primer coat.
After priming and drying, apply the first coat of Sikalastic-488 generously with a roller, making sure you go up walls and edges at least 100–150mm. Once that coat has cured, apply a second coat at right angles to the first to achieve full coverage and the correct thickness. Because the surface will remain exposed and walked on, lightly broadcasting fine sand into the second coat while still wet can improve grip and durability. Taking your time with cleaning, priming and applying generous coats will make a big difference to longevity and help achieve a durable, professional-quality result.
If you need further assistance, please let us know.
Eric
Absolute legend, thank you so much for such detailed step by step instructions. Now keen to kick off the project :)
Please don't forget to post a picture of the balcony when you've finished your project. You know how we love a good before and after pictorial here on Workshop.
Thank you
