How to choose roof-deck waterproofing so it doesn't leak again! Each system in depth, plus the answer: can homeowners really apply it themselves?
A leaking roof deck is a nightmare for owners of shophouses and modern-style homes. Every time it rains, water seeps through cracks and damages the ceiling and furniture below. Applying a roof-deck waterproofing system is therefore an important step you shouldn't skip. The popular question is which system to choose, and whether homeowners can buy the product and apply it themselves.
Comparing 3 popular waterproofing systems for roof decks
Before you buy materials, let's get to know the waterproofing systems commonly used in Thailand, so you can choose one that fits your budget and use:
- Acrylic waterproofing: the easiest to use and the cheapest; suits roof decks with a good slope and no standing water; dries fast and is easy to apply yourself
- Polyurethane (PU) waterproofing: very flexible, bridges cracks well, resists sun and rain, and handles water pooling at the edges better than acrylic; suits roof decks that take heavy use
- Cementitious waterproofing: resists abrasion and water pressure well; good for applying before laying tiles on top, or on damp concrete surfaces
Can you apply it yourself? Check you're ready before you DIY
The answer is "yes, you can" if you're repairing small leaks or a roof deck that isn't very large, using a brush-on product such as acrylic or PU. There are key steps you must follow strictly:
- Clean the surface: Scrub off all moss, dust and oil stains, and let the surface dry completely before you start
- Seal the cracks: If there are cracks wider than 1 millimetre, fill them first with a joint filler such as PU sealant before applying the waterproofing
- Lay fibre mesh: lay reinforcing mesh over joints, corners and cracks to strengthen the coating so it doesn't tear easily
- Apply at least 2-3 coats of waterproofing: apply the first coat and let it dry, then apply the second coat at right angles to the first so the film covers completely
Warning! Jobs you shouldn't do yourself and need a tradesperson for
Applying waterproofing may look easy, but for the safety of your house and yourself, there are several situations where DIY is definitely not recommended:
- Large cracks or spalling concrete: if you can see the steel inside so rusted that it has pushed the concrete apart, that is a sign of structural failure — call an engineer or structural tradesperson to repair it immediately
- Water seeping near electrical systems: if the leak runs through light fittings, cable trays or a distribution board, don't go near it until the power is cut, to avoid the danger of current leakage
- Large roof decks or torch-on membranes: torch-on waterproofing needs expertise and a flame torch to fuse the sheets; leave it to specialist tradespeople only
In short, if the roof deck is small and the leak isn't complicated, you can buy a waterproofing product and DIY it over a weekend. But for large jobs, structural problems, or work at height without safety equipment, hiring an experienced tradesperson gets the job done properly, safely and more cost-effectively in the long run.