How to repair water damage to sub floor next to sliding door?

[diyaaron]

We have a sliding door that backs onto a deck, and we have had persistent issue with water damage to the house subfloor along this wall. The wall is externally clad with weatherboard.

The yellow tongue sub floor has suffered water damage sufficient to need replacement. The perimeter wall and sliding door is built on the subfloor.

I wonder is there a higher grade subfloor I could use for this area? Red tongue? Also, is there some sort of flashing I should use over the Junction between our wall/subfloor and the deck. Thirdly, what nails should I use to reframe this wall after replacing the subfloor, I plan on hiring a nail gun from bunnings for this project.

[MitchellMc]

Hi @diyaaron,

It's important to address the root cause of the moisture entering your subfloor, as simply repairing the water damage won't solve the ongoing issue. Moisture can infiltrate through various pathways, including inadequate flashing around the sliding door, poor drainage on the deck, or even from the wall itself if there are gaps or breaches in the weatherboard cladding. Without properly identifying and resolving these issues, you risk significant damage to the timber frame and subfloor in the future.

Regarding your questions, while you could consider using a higher-grade subfloor like red tongue, it's essential to understand that enhancing the water resistance of the particle board may only serve to disguise the issue.

In terms of flashing, it’s highly recommended to install flashing over the junction between your wall, subfloor, and the deck. Properly installed flashing will help direct any water away from the wall and prevent it from pooling at the base, which can lead to further moisture intrusion. Ensure that the flashing extends far enough out to deflect water away effectively.

As for reframing the wall after replacing the subfloor, you can use galvanised nails or stainless steel nails to prevent rust and ensure longevity, especially in areas exposed to moisture. If you plan to hire a nail gun from Bunnings, ensure you get the appropriate gauge nails recommended for framing, typically 75mm, depending on your specific framing requirements.

Ultimately, while these solutions can help with the immediate repair, it’s essential to focus on preventing water ingress to safeguard your home against future damage. Consulting with a professional for a thorough assessment of the underlying issues may also be beneficial before proceeding with repairs. 

Please let me know if you have any questions.

Mitchell

[diyaaron]

Thanks mate.

There are some holes in the weatherboard near the area which I suspect is the main culprit, which I'm fixing, but I cannot see any sort of flashing which I assume is also contributing. 

Any guides/advice on flashing?

[MitchellMc]

That's difficult to answer without taking a really good look at the area @diyaaron. Is the deck connected to the house with a ledger board? If so, is there a flashing between it and the house or at least a gap? 

Mitchell