Thread: Floor for external balcony

First I'll start by saying I can't answer your spcific question but I wanted to describe my exact same situation.

We bought a house last xmas and when the rains came we discovered leaking into the downstairs from the upstairs deck.

I hired a demo hammer and lifted all the tiles (36sqm) and then spent a day in hospital with a racing heart courtesy of the using the hammer.

I hired a concrete mower to remove all the mortar and returned the sheeting to a smooth service.

I located the damaged areas and on lifting the sheeting I discovered the rotting joists and bearers underneath.

I called the pros and they replaced the timbers and cement sheeting.

I can't say what they used it appeared lighter and less dense than the original, they nail gunned it rather than screwed it, it was tongue and groove, similar to the link you sent. So it may have been the same.

I then applied a membrane (Bostik Ultraseal) laid battens and another coat of membrane over the battens, then laid decking boards.

Fingers crossed this will last for a while.

A previous post shows the old and new deck, and the photo below is the completed product with some furniture.

Cheers,

https://www.woodworkforums.com/f330/deck-underfloor-questions-57362

Simple - follow manufacturers advice and use compressed sheets - the Sycon is for internal use only and will lose any guarantee if used externally as in your deck (and contrary to specs).

See:

http://www.jameshardie.com.au/Produc...llationManual/

This stuff is easy to install and there are various levels of sealing during construction to provide water resistance up to fully waterproof.

Most likely you will need only to replace joists that are under joins in the original and possibly by simply adding new joist adjacent to the existing one rather than removing the old ones.

If the ceiling underneath is accessible and plasterboard you might be better to remove it to inspect what state the joists are in - if they are mostly OK then you could re-sheet over the existing fibro sheeting.

Depending on the age of the deck the sheeting might be asbestos - quite safe so long as you do not drill, cut or sand it, but a good idea to have it removed safely anyway (and each state has rules about who and how).

It ought not to be too hard a job though - if the existing sheets are screwed or nailed then you just remove one row of sheets at one end, do the needed repairs to joists and place new sheeting back on then do next sheets working of the new ones. Following the instructions for edge joint sealing and then you can use a brushable urethane membrane over the top when all sheets have been replaced.

Summary - do not use sheeting designed for interior work regardless of a tradey saying you can - it means that you then rely on the membrane when in fact your should have a complete system that gives you the service life and performance you need for exterior use.

That sums it up nicely Bloss. You'll void any warranty, implied or written, if manufacturers' specifications are not complied with.
It may be highly unlikely that you'll have any problems, however if it was guaranteed, then Hardies would sell the sheets for external use.

I know who I'd rather be chasing if I had a failure somewhere down the track, and it's not some builder who may be bankrupt, or unreachable by that time.

I am a bit confused about this Scyon sheeting. I read the tech data posted and yes it says "internal". But they use thinner Scyon panels for facards and general external walling. I might phone Hardies on Monday to find out what they say. I'm curious myself.

It's certainly much easier to use, being lighter and nail fixed.
It would be more porous and less waterproof than compressed though. If the membrane does get punctured or scratched by a tiler, I'd rather have compressed under it, but then again a shower recess would see a lot more water than a deck.
I don't really know what their reasoning would be.