ᐅ Ventilation of Wooden Decking

Hello everyone,
I have a concrete balcony that was extended with wood.

The space under the extension should be protected from rain.
My plan: On top of the beams, I will install a 1.5 mm (0.06 inch) pond liner. The slope of the beams is 12 mm per meter (0.5 inch per 3.3 feet) towards the lawn. On top of that, there will be a rectangular aluminum profile measuring 60 mm by 20 mm (2.4 inches by 0.8 inches; W/H). My Cumaru FSC-certified decking boards will be fastened to this profile using hidden fasteners, which add an additional 5 mm (0.2 inch) in height. This means I have a total gap of 25 mm (1 inch) above the pond liner to the decking boards.

My question: Is a 25 mm (1 inch) gap between the liner and the wood sufficient to ensure proper ventilation for the decking boards?

What kind of foil!?

A black pond liner used to line ponds.

Why shouldn’t that be sufficient? What’s important is that the floorboards don’t stay wet and can be ventilated. Both conditions are met in your case, so thumbs up.

Hello,
I thought it was too little.
I will do it this way now and upload the result afterwards.
Thank you for your opinion.