How to build a low-level deck?

[IronStan001]

I have an alfresco area which I'd like to deck.  The joists (Green lines) will most probably fix straight into the concrete and ideally, I'd like to go 1500mm beyond the concrete (Red line).  I have a storm water pipe (White line) about 800mm out from the concrete.  800mm out from the concrete, the ground is at its lowest point, which is about 200mm lower than the alfresco.  With regards to the footings and bearers, what are my options?

Community manager's note: Check out How to build a low-level deck for expert advice.

[IronStan001]

I'd think a ledger board, one either side of the downpipe.  A board that's 200mm tall should be ample.  At least 180mm of that will be below the brick, so any screws or dynabolts would be going into the slab for a strong fix.  The joists could be secured using joist straps:

https://www.bunnings.com.au/pryda-joist-strap-162mm_p1121966?region_id=116395&gclid=EAIaIQobChMIrNLo...

Does that sound suitable?

[MitchellMc]

Sounds like it would work, @IronStan001!

Mitchell

[IronStan001]

OK, so, this is what I'm up to:

120x45mm F7 H3 joists @ 450mm centers.  To prevent joist twisting, 90x45mm noggins at around 1300 to 1400mm.  Packers (Macsim 75mm 600 Piece Mixed Window Packers - Bunnings Australia) to be used under the joists where needed for some extra support.  Bearer will be (at this stage) double 90x45mm F7 H4 @ 1400mm treated sitting on 4 posts about 1460mm apart.

Fixing the end joist to the column using a Pryda Joist Hangar should be suitable to allow me to work around the downpipe.  The joist will be positioned as close to the downpipe so as to avoid drilling and screwing close to the edge of the brick.  If that isn't suitable, a 90x90mm post would be fixed into the slab and notched to support the joist.

Boards will be 140x19mm, level with the internal floor:

 I'm still not 100% sure on finish of the boards.

[MitchellMc]

Good stuff @IronStan001.

Personally, I like the right-hand side with the fascia board picture framing the deck. Looks great on the side face and adds a little extra appeal to the top.

Mitchell

[IronStan001]

Agree with the picture framing.

Is 1300/1400mm spacing of the noggins adequate?

[MitchellMc]

That's fine @IronStan001. The decking itself will provide significant rigidity to the joists.

You could offset the noggins further from each other though, they work best if they aren't in a straight line.

Mitchell

[IronStan001]

Noted.  I'll stagger them a little more and also include some within the span over the soil.  Aside from the particulars of the fixing hardware, I think I'm good to go.

Because I'm having the bearer sit on stirrups, I think constructing the deck in reverse would work well.  That'd be:

• Dig the holes for the stirrups where needed.
• Install 4 or 5 joists
• Hang the bearer off the joists
• Fix the stirrups to the bearer
• Fill the hole with concrete as needed
• Complete the rest of the deck

I think that way, I wouldn't need to stress so much about getting the levels right for the stirrups if I was to do them first.

[EricL]

Hi @IronStan001 

Sounds like you have your decking assembly all worked out. To help you with the stirrup levelling, I suggest using an Empire Post and Pipe Level along with an Empire Lightweight Line Level. These levels in combination with a builder's line will help you make sure that everything will be level and square. 

My best advice is to test the layout of the frame before anchoring everything in place.

If you need further assistance, please let us know.

Eric

[IronStan001]

When fixing the angle brackets to the joists, would there be any preference as to what to use?  Bolt and nut, or batten screws?

[MitchellMc]

Preferably a bolt @IronStan001. That's would be far more secure than batten screws.

Mitchell