What this work covers
Balcony waterproofing starts after demolition and floor repairs are complete. The installer reinforces vulnerable areas around the drain, wall base, window frame, and corners, then connects the sheet membrane and urethane coating into one continuous layer. Falls and surface condition must be approved before tile conceals the work.
When this work is needed
A balcony extension, full tile removal, or work that disturbs the drain or window perimeter usually requires a new waterproofing scope and junction details. If the repair only replaces a small area of finish while the existing membrane and drainage remain intact, do not commit to full replacement immediately. First check the leak history, the damaged area, and where water is actually collecting.
Decide before work starts
The product name does not define the finished system. Agree on these points before signing the contract.
- How far the waterproofing extends across the floor, wall base, window frame, and drain perimeter
- Where the sheet membrane and urethane coating are used and how they overlap
- Which materials reinforce corners, joints, drains, and other vulnerable details
- How the finished surface will be prepared to receive tile
- Who approves the falls, sheet joints, and coating before tiling begins
Check in the quote
Use these questions when you review the quote.
- How much substrate repair and correction of the falls after demolition is included?
- Are the sheet and urethane coverage areas marked on a drawing or site photo?
- Are the materials for joints, corners, drains, and the window base specified?
- Does the programme allow for drying between coats and final curing?
- If pinholes, lifting, or ponding are found, are repairs and reinspection included?
If you have photos of the balcony floor and window base or the waterproofing quote, I can help you check the vulnerable details and the proposed sheet and urethane coverage.
What to check on site
The broad floor is rarely the only concern. Waterproofing most often fails where materials and planes meet, especially below the window, at corners, and around the drain. Check that the substrate, sheet, and coating form one connected system.
- Base and Weak-Point Cleanup Complete
Remove dust and weak mortar, then confirm that the substrate is dry enough to receive the membrane. Repair cracks and gaps around the wall-to-floor corners, drain, and window base, and mark both the required upstand height and every reinforcement area before covering them. - Self-Adhesive Sheet Waterproofing Complete
Bond the self-adhesive sheet without wrinkles or trapped air, and overlap the joints so the edge does not face the direction of water flow. Use the specified reinforcement around corners and the drain, press every edge firmly, and inspect the full perimeter for lifting. - Urethane Coating and Finish Check Complete
Apply the urethane coats evenly over the sheet, observing the drying time for each product and layer. Under good light, look for pinholes, bubbles, thin areas, or coating that blocks the drain. Run water across the finished surface to confirm both the falls and drainage.
Where problems usually start
- Sheet joints Short overlaps or poor pressure along the edge can allow the sheet to lift and water to track underneath.
- Floor falls A shallow or reversed fall leaves rainwater standing and increases the risk of leakage and staining.
- Urethane surface Pinholes, bubbles, and visibly thin areas can become water paths after repeated weather exposure.
- Surface below the tile Unevenly scattered aggregate can leave an inconsistent key and adhesive thickness below the tile.
A leak mark does not prove that the floor membrane is the only cause. Window sealant, exterior-wall cracks, the drain connection, and the floor falls should be checked separately before repairs are specified.
If a sheet edge has lifted or the coating contains pinholes, pause the tile work. The waterproofing and tile contractors should agree on the repair area and the reinspection method before anything is covered.
Timing and records
Allow roughly four to eight hours for active work, but substrate drying, drying between urethane coats, final curing, inspection, and repairs are additional. Rain, temperature, humidity, and the product specification can all change when the balcony is ready for the next trade.
Keep the product and batch details, marked waterproofing area, close-up photos of sheet joints and reinforced details, the finished urethane surface, falls, and any repair locations. Once tile covers the system, these records are the clearest evidence of what was installed.
Balcony waterproofing follows demolition and must be approved before the new tile finish is installed. Reviewing both adjoining stages helps prevent a weak junction from being hidden.