Leaking Timber Deck

[Deza]

I have a dilema with a timber deck in a house I have recently bought. The deck is above a garage but only has tounge in groove timber for the flooring so whenever it rains water goes straight through to the garage.
I have a couple of ideas re what might be the best way out:
1) line the timber with black plastic and then concrete over the top with a slope on the concrete to drain off. Then put a waterprrof membrane over the concrete and then tile. This will be the cheapest option.
2) lay ceramic tile underlay then concrete for a slope for drainage, then waterproof, then tile.
3) Lift the tounge in groove timber up and lay compressed fibro, then waterproof, then tile. This is obviously the most expensive and time consuming option.
Basically I am after advice - will option 1 work? If not why not? What sort of waterproofing products should I use?

Any advice, or new ideas much appreciated.
Deza

[craigb]

With luck, Journeyman Mick will answer this for you. My guess would be though that he will go for option 3 because that's the proper way to do it.

[seriph1]

there are flexible waterproof membrane products that can be applied directly to timber substrates - if you must, this might be the way to go ..... but first, you will need to assess the fall of the floor.
Also, what is the construction under the floorboards? You mentioned tongue and groove up top, so I am thinking bearers and joists...? FInally, had you considered building a roof over it?

[journeyman Mick]

Deza,
this sounds like a real "what the hell were they thinking when they did that?" type situations. Option 1 was used a lot in the past for bathroom floors (without a membrane as they were not yet invented or common use anyway). All 3 methods would work but I would go to a reputable tile supplier and ask them to reccomend a total system, ie: underlay & proprietry topping & compatible membrane, adhesive, tiles & grout. Seriph's idea of fitting a roof has a lot of merit. By fitting a roof you would minimise the amount of water landing on the floor and probably keep it flat. I did some work on a house in Cairns (one of the highest rainfall areas in Australia) that had a roof over a flat compressed fibro floor with a membrane and textured decking paint on top.

Mick

[bitingmidge]

Couple of things to be wary of:

Make sure that the timber is completely dry all the way through before you put anything over the top which will keep moisture in it (as well as out of it!)...if water is getting through it now, there is a fair chance that some of the timber in the joints has been damp for quite some time, and you have a perfect spot for dry rot.

The weak spot in installations like this is always the wall/floor join...if you don't provide a joint which allows for some movement, it WILL crack and leak!

Cheers,

P

[ozwinner]

the joints has been damp for quite some time, and you have a perfect spot for dry rot.

OK, Im as confused as ever, I still cant work out why when its damp, do they call it DRY rot..? :confused:


Al

[jackiew]

i believe that its called dry rot because it can spread its nasty horrid tendrils from the damp source to dry areas - including passing though brickwork

[ozwinner]

Oooh bugger, so thats what Ive got?


Al

[bitingmidge]

No no no Oz me old mucka, just because you have "nasty horrid tendrils" doesn't mean that you have dry rot, it's probably from morphing into all those different characters.

"Dry rot" is really not that common in Aus (at least the parts I come from), and it is common for all rot in seasoned timber to be referred to as Dry rot even though it isn't!!

Wet rot is fungal decay caused by a fungus which requires moisture;it's a mushroom in a different guise! (often this is found after some activity in dormant form in dry timber, and is wrongly called "dry rot" but ignorami like myself!

Dry rot is fungal decay caused by a particular fungus which is able to spread over DRY non-wood surfaces,(like brick walls...echhhh!!) transporting its own moisture and advancing up to several metres beyond its food source (the wet bit) - like other rots, it needs moisture but can spread over and colonise dry surfaces to some extent; it's a nasty basket, that just won't go away until you kill all the spores everywhere!!

Yours sincerely
Fungus Features

[Theva]

Deza,

As Mick said check with some tile / glue mob, ABA & Daveco web sites have lots of info.

Option 2 is the most likely solution but without the concrete bit, you need something flexible. Future maintenance will be an issue if you do not have access to the underside of the deck.

Regards,

Theva

[Deza]

Hi all and thanks for the ideas and commentary re dry rot/wet rot,
Another question: - if I lay the plastice then concrete, will it sweat?

[bitingmidge]

Another caution on the concrete:

Often timber decks are constructed very lightly (ie with light timber members) and are not capable of holding significant dead loads (the load of the structure).

Please...make sure that the existing framing is up to it, if you are going to use a reasonable thickness slab.

Cheers,
Dr Spoilsport.

[jackiew]

for anyone who hasn't encountered an old house with dry rot ... it smells ... some people say its like mushrooms ... but once smelt never forgotten. Typical place to encounter it seems to be the cupboard under the stairs.

Would agree with biting midge that you should be cautious with regard to loading your deck with weight ... you don't want half a ton of concrete and timber landing on the car parked underneath :eek: ... or on someone standing under there undloading the groceries :eek: :eek: