deck with no clearance over concrete slab

**gsouth** · 5th March 2007, 10:12 PM

Hi all,

I have just about finished a deck and have had a change in plan for the final piece. (nothing like last minute changes to throw a spanner in the works)

One section of the deck was due to finish flush with an existing concrete patio. This part of the deck is std bearer/joist construction.
We are reviewing extending the finished section about 800mm over teh concrete patio. Teh clearance here would only be about 80mm to the concrete underneath.

Is this possible with such little clearance? If so how do you go about having the joist sit directly on the concrete?

This is a rough explanation of what I'm trying to explain (J=joist)

PLAN

J....J....J|
J....J....J|
J....J....J| <- edge of deck finshes at concrete patio
J....J....J|

J....J....J|....J
J....J....J|....J
J....J....J|....J <- edge of deck extended over concrete patio
J....J....J|....J

**Pulse** · 5th March 2007, 10:45 PM

This post has ben visited a few times, a good post was about using threaded rod.
Chemset small lengths into the concrete and use nuts and washers to attach the joists above them. Only works on low decks since there is no bracing, and it probably wouldn't pass building inspections unless someone had an engineer analyse it.

Good luck
Cheers
Pulse

**gsouth** · 6th March 2007, 10:03 PM

Thanks - yes I read this post earlier, however my clearence is only around the 80mm mark, so I won't even have room for a full joist laying hard on the concrete, let alone having one suspended using the method mentioned...

Is it possible to have treated pine directly on the concrete slab secured down using brackets?

Geoff

**richo69** · 8th March 2007, 06:01 PM

i think you need H4 if you are putting it directly on ground. you also need to be sure you have adequate drainage between the joist so water wont pool
richo

**dazzler** · 8th March 2007, 06:13 PM

Sounds like

rat a tat tat - rat a tat tat

**UteMad** · 8th March 2007, 06:49 PM

we"re doing it all the time with decking over concrete.... was your height of 80mm to the top of the joist or the top of the decking????
If it was the joist use treated pine 70 x 45 on edge sitting on a 10mm horse shoe packer that give 80mm .... If you want to fix it down use galv dyna bolts and speed bore the head into the top of the 3 x 2 ....
If it was 80mm to the decking use 3x2 on flat with 15mm of plastic packing or mac wedges same fixing method but you'll have to pack more frequent.....

Even harder try doing a set of concrete stairs like i did today with battens ... Looks good in the end

Forgot to ask hopefully we didn't quote it as i noticed your in Sydney

Ute Mad

**Impalaman** · 17th March 2007, 04:55 PM

UteMad,
Thanks for the info, excuse my ignorance when I ask what exactly is a horse shoe packer and what fixing distances into the concrete would you recommend?

**UteMad** · 17th March 2007, 05:50 PM

Originally Posted by Impalaman

UteMad,
Thanks for the info, excuse my ignorance when I ask what exactly is a horse shoe packer and what fixing distances into the concrete would you recommend?

No probs

A horse shoe packer is a plastic packer in a u shape approx 50mm x 80mm and come in thickness of 1 3 5 10mm thicknesses.... you can buy them off some hardwares in a mixed bag for 40 bucks or so.... the groove they have up the middle is big enough to slip around a 10mm dyna bolt.....you add the combinations to get what ever thickness you need

If your using 90 x 45 batten every 1200mm or so if a 70 x 45 batten the you can do either 800mm fixings or 1200mm and just packer the centre without a dyna bolt to take out the bounce ( glue it in with eurothene instead )

cheers ute mad

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