No Clearance Timber Deck

[Ideas Man]

Posting for the first time......

I wish to construct a small deck 3500 * 3500, over a concrete slab(sounding familiar). I have read a number of other posts but none seem to provide any real answers to my predicament.

Here goes....

1400 of the 3500 only has 30mm clearance, when I take a decking board into account (18mm), I only have 12mm to play with on this area. This is due to a major engineering effort to get the slab to this level, I couldot push it any further. Retaining wall issues... but that is another story. The clearance comes about by wishing to eliminate any step in the courtyard and this 30mm places the deck at the same level of the house floor. (Land area is only 45sqm so this external space is extremely important) Yes that is right 45sqm.

As I see it I have 4 possible options, the 5th - pavers is not an option as dictated by the other half. All revolve around batons.

Options as I see them.
1. Would love to use something like Dektrac http://www.dektrac.com/Dektrac%20-%20the%20product.htm, but it is not in production. Would love to know of any alternatives. Any form of steel baton would do and really prefer to be screw/nail less finish
2. I could use some sort of 10mm Polyurethane as the baton. Thinking of water rot/rust resistance here.
3. 10mm T/P Timber baton, with all the waterproofing membrane, etc..
4. The tile deck construction I read about in a previous thread would also work, but the least preffered option, but does have some practical merits.

So the remaining 2100, has a clearance of approx 70mm, again an issue, but no where as bad as the first. I can work around this one with timber joist and bearers against the step in the slab and the house, also on a slab.

Other points to keep in mind....

The 1400 *3500 slab area is pretty level and has a tendancy to pool a little water, I have yet to consider the alternatives here, although that is why I am leaning away from timber batons. It might help when I clean this up as it has some left over cement/concrete lumps from the wall construction.

The 2100 * 3500 has very good drainage, so water no real issue here, just need to pack under the joists. and they would be raised above the draining water.

I guess this means I am looking at 50mm joists for the 2100, would this be OK??? I could add another bearer to bring the length of the joist down to 2* 1000mm of so. Or 40mm if I continue the baton choice from the above 1400.

Proposing to use Blackbutt decking with 1 - 2mm spacing and a smooth profile. Oh and also, would like the finish to be nail/screwless.

Totally exposed to the elements, although very quick drying. There is an annoying tree dropping leaves as well, so constant sweeping required to get the buggers of the deck.

After reading this I could be called the No Ideas Man or maybe just a dreamer.

Any helpful suggestion apprreciate and I hope to be able to repay the favour one day.

[SilentButDeadly]

how about something like a boat deck finish on the very low clearance part? Basically put a levelling compund on the slab to smooth it out and bring it up a bit, waterproof it as you would a shower, glue down your timber, seal the joints with black Silastec.

It's a bit hard to visualise this space...so it's hard to visualise a solution...but I'd still be looking at the raised dias look rather than what you are thinking...if timber is the required finish...

A steel sub-frame is certainly possible though.....trick is how to bolt it down with the timber in place (to get the no fixings look)

[Dirty Doogie]

A pic of the site would be of use here.

With very low decks I always suggest treaTed pine decking sealed with Bitkote on the underside (maybe stained on top to match existing decking) - It is going to get pretty wet and mucky under there. Dirt and grit and all sorts of debris falls between the deck boards and builds up in the space underneath. The only way to clean it out is to flush with garbage bins full of water.

Blackbut decking is going to need mechanical fixing in your situation. The difference in moisture levels above and below the boards is going to make them go crazy in terms of movement.

I would be thinking about making the deck in 2 or more sections and using galvanised c section battens and screwing the boards from underneath. This means each section has to be premade and flipped /man handled into place.

[Ideas Man]

Dirty....

Can you confirm a couple of things for me....

When you state Blackbutt would require mechanical fixing, do you mean screwing to the suggested steel C baton? I have more or less resigned to the fact that I will have to prefab this and lift into place to achieve the screwless look. The other alternative is to screw the screwless and go conventional.

One more thing, ready your post it implies that TP is less likely to move as much as blackbutt. Is this the case??? I was looking for a hardwood rather than softwood, thus the balckbutt. Alos looking for a blonde or light timber finish to match bluackbutt flooring insode.

Thanks for the info so far.

I will steer away from the boat deck finish suggested, purely on the basis of the moisture issues already raised and lack of confidence in glueing the boards down.

I will attempt to get some pics on board

[Dirty Doogie]

Hardwood in high miosture conditions can start bowing and cupping and splitting in my experience - hence it really needs to be very strongly fixed in position. Screwed from underneath will do it.

The treated pine will expand and contract - even more than Hardwood in your conditions - but it wont rot - that is why I would recommend it in very low decks or straight onto the concrete.