From Mystery Leaks to a Nail-Sized Culprit: Diagnosing and Extending the Life of a Direct-Fixed Deck
Diagnosing and Extending the Life of a Direct-Fixed Deck
The owners of this property had ongoing water ingress from their deck. In attempts to solve it, they applied black bitumen waterproofing and plenty of silicone, but the leaks persisted. Other professionals had investigated without success. When we arrived, we initially assumed the entire tiled deck might need full uplift and re-waterproofing. But we decided to check behind the weatherboards first.
We found that the weatherboards were installed right down onto the tiles, with no gap. The boards were pressed against the butynol waterproofing underneath. This created a capillary action: when water reached the weatherboards, it was drawn upward between the board and the butynol. We saw staining and dirt lines showing this water pathway. Even worse, nails used to fix the weatherboards had penetrated the butynol. One nail had rusted away, creating a direct pathway for water.
We see this type of issue quite often on older direct-fixed decks
Here’s the interesting part: when the weatherboards were still on, water would be sucked up through capillary action, reaching the nail hole. When we tested the area by spraying water with the boards intact, the leak appeared. But once we removed the weatherboards, we sprayed again in the same way, and the leak stopped. Without the weatherboard in place, the capillary action was broken, and water couldn’t rise to the nail hole. Only when we directly sprayed at the nail hole did water reappear inside.
Butynol is a good waterproofing membrane, but it does have a lifespan—often around 20 to 30 years. In this case, the butynol was compromised by nail penetrations. While newer solutions like TPO are gaining popularity for durability, we were able to extend this deck’s life. We filled the nail holes and applied new butynol over the top. This avoided the need to uplift the tiles, giving the owners more time before a full upgrade. This deck was built in the era of direct-fixed tiles, and now, with a targeted repair, it’s watertight once again.
In the end, this was a great example of how thorough investigation saved unnecessary work. Sometimes, all it takes is finding the smallest detail—like a nail hole—to stop a major leak.
