How to seal timber decking to stop leaks?

[simon55]

Hi

i I live in a 2 storey house which has a balcony. It has timber decking & a roof. However when rains the water pools on the deck and leaks to the bottom floor which I converted into a man’s cave.

is there any appropriate material that I can lay over the decking and seal it with a membrane? Love to hear your suggestions.

thanking you

[EricL]

Hello @simon55 

Welcome to the Bunnings Workshop community. It's sensational to have you join us and thanks for sharing your question about your deck.

I suggest having a quick look at this discussion - How to waterproof under deck? by @Bubbles8712. It's an excellent example of how you can keep the bottom of your deck dry without having to modify the decking panels at the top. I believe this would be a better alternative to covering the decking panels. Generally speaking, the proposed idea is to use corrugated panels under the deck to guide any water falling through to the outside. A fall must be installed into the corrugated panel so that water does not pool on its surface,   

Let me call on our experienced members @Dave-1 and @Nailbag for their recommendations.

If you need further assistance, please let us know.

Eric

[Bubbles8712]

Hi Simon55. I actually ended up scrapping my original waterproof idea with mounting panels underneath the decking. The main reason being that decks are meant to be open underneath to allow air flow/ventilation to prevent rot. 

I ended up doing a membrane system involving rubber pond liner. I unscrewed all decking panels, cut pond liner and stapled this to the joists (cut in a fan shape to enable fall), installed a gutter system to take the water away, re-screwed the decking. 

I didn’t take progress shots along the way but have linked a couple of videos that illustrate it quite well. One of the videos shows the pond liner being laid in one large sheet. I suggest measuring the width of your joists and cutting the pond liner to suit each one. Takes more time but helped ensure a consistent fall for each section. 

You could do this as well and then mount some colourblind sheets underneath so when sitting in the man cave, you’ll see the sheets as opposed to the pond liner. 

Given your deck has a roof, the original idea might still be okay if it only gets light rain. 

 

https://youtube.com/shorts/yX0d7yaX464?si=F8JARnsl4yiTMzGd

https://youtu.be/cDmXxTk-ZKs?si=45sHMyaBdAfqdhWM

[EricL]

Hi @Bubbles8712 

Thank you very much for that update. It's good to hear that you've managed to cover the bottom of your deck in another manner. Let me tag @simon55 to make them aware of your recommendations. I love that the pond liner doubles as a joist protector as it keeps the frame of your deck dry. This should add years to the service life of your deck.

Eric

[Dave-1]

Morning @simon55 

I dont know of any material that can/should be laid over decking to make the underside waterproof. 

I have seen the way @Bubbles8712 has suggested and that looks liek it wiorks (Its how I would approach it myself)

The only other thing and its a short term solution is to put up some clear plastic rain protectors on your decking area so the rain dosnt make it to the decking itself. Something along the lines of these Marquee PVC Outdoor Cafe Blind - Clear 3000mm x 2400mm 

A few photos showing the overall area, and where the water is coming from and leaking through would help us come up with some other ideas  

I would also like to say Howdy and welcome to the community There are a whole bunch of possible solutions amongst these pages. Hopefully a few of them will lead you towards an answer

Dave