waterproofing a deck

[SlowWorker]

I have a pole house with 2 decks with a roof above th top deck.
I want to waterproof the top deck and convert the lower deck to a bedroom.

I had planned to re do the top decking (cedar boards) to narrow the gap to about 1 or 2 mm and using a caulking compound (marine strength) to waterproof it.

I have read thye forum msgs on waterproofing but havnt seen this solution am I doing the wrong thing?

I have worked on sailing yachts that gave caulked timber decks and can take considerable pounding by sea water but a builder I spoke to thinks it may not work but does not know why - just says it isnt done.
Anyone know why it doesn't work?

[justinmcf]

timber contracts and expands. this is not good for water proofing.
i am sure your builder advised you to use fibre cement (fc) sheeting. 16mm-18mm fc sheeting is best.
but you have to be careful not to overload your flooring joists.
are your joists hardwood or softwood?

what are the dimensions of your flooring joists?

1. length?
2. height?
3, thickness?


regards, justin.