Low-level composite deck on soil and concrete

[nvdshams]

Hi

I have recently gathered enough courage to build a low level deck that is going to be partially on concrete and and soil. Got the confidence that I can build it after seeing so many amazing projects on this site. This is how it currently is

On top of the concrete I just have 100mm to build the deck on. I was thinking of bolting 70x45 timber using angle brackets. Adding 23mm of Ekodeck on top of it gives me clearance of just 7mm. I hope that is enough for the water to pass through.

One of the challenges I am facing is the weeping holes on the bottom of the wall. I can't block them so have to put pieces of wood around them.

I will be using Dunnings 50 x 100 x 50 x 5mm M12 Galvanised Angle Brackets and Ramset 12 x 60mm DynaBolt Plus Hex Nut Bolt to fix the timber on the concrete.

I am using a 90x45 (A13) to transition between concrete and soil. That is also going to be attached to the rectangular column for extra support.

Joists are placed 350-420mm apart. Joists on both edges are 430mm apart to make room for the triple border. Noggins will be attached using Zenith 14 - 10 x 125mm Galvanised Bugle Head Batten Timber Screws to support the triple border.
For drainage, I will be installing Vinidex 65mm x 20m Draincoil With Filter Sock around the concrete. I need to be careful not to place pavers and mini foot on top of it.

Deck layout:

I have got a few questions and would appreciate if the experts can help me with those:
1. How to connect 70x45 joists with 90x45 (orange chevron)? I can't seems to find a 45x70 joist hanger. Should I use 45x90 joist hangers with a 20mm piece of wood tuck under the joist?
2. How do I attach two outer timbers to the rectangular column? And how do I place A3 and B3 around the column?
3. Do I need extra support for noggins between A1 and A2; and B6 and B7? Those noggins are there for the triple border. Should I bolt them to the concrete and put mini foot on the soil?
4. There are 4 weeping holes on the wall. That is why I have to break B7 into 5 pieces. Is that ok?
5. Which drill bit should I use for Ramset 12 x 60mm DynaBolt Plus Hex Nut Bolt?
6. For timer to timber connection on angles, I will be using Carinya 50 x 50 x 40 x 1mm Galvanised Angle Brackets (green angles in diagram). Is 1mm thickness enough?
7. Can I use 45 x 90mm joist hanger to join 90x45 to 70x45 (yellow chevron)?
8. The span on 90x45 joists is approx 1400-1500. Is that a big gap?
9. What do you recommend how far away to put noggins between joists?

Apologies for asking too many questions.

Material

Timber:
90 x 45 framing MGP10 H3 treated pine
70 x 45 framing MGP10 H3 treated pine

Angles and hangers:
Carinya 50 x 50 x 40 x 1mm Galvanised Angle Bracket (green angle in diagram)
Pryda Joist Hanger - To Suit 45 x 90mm (blue chevron in diagram)
Dunnings 50 x 100 x 50 x 5mm M12 Galvanised Angle Bracket (red triangles in the diagram)

Screws and bolts:
Pryda Timber Connector Screw 12G x 35mm Hex Head Box 250 (for connecting joist hangers and brackets to timber)
Ramset 12 x 60mm DynaBolt Plus Hex Nut Bolt
Zenith 8 - 10 x 30mm Treated Pine Countersunk Head Screws
Zenith 14 - 10 x 125mm Galvanised Bugle Head Batten Timber Screws

Support on soil:
Brighton Masonry 300 x 300 x 40mm Charcoal Mypave Paver
Builders Edge 25-40mm Minifoot Pedestal Feet (black circles in diagram)

Drainage & weed control:
Vinidex 65mm x 20m Draincoil With Filter Sock
Pillar 0.9 x 25m Black Jumbo Weed Control Mat
Ki-Carma 20kg 10-20mm Drainage Gravel
Whites Weed Mat Pins - 20 Pack

Misc:
Ekodeck Quickfix 3mm Quickfix Kit - Timber Joists
137 x 23mm 5.4m Decking Alpine Ash / Ironwood Composite Ekodeck Designer
Crommelin 1L Exterior Grade Brushable Waterproofer

[EricL]

Hello @jigz 

Welcome to the Bunnings Workshop community. It's wonderful to have you join us, and thank you for sharing your question about your low-level deck.

Let me try to answer some of your questions.

• The Pryda Joist Hanger - To Suits 50 x 60mm looks promising, but I will have to check with Pryda if your installation idea is viable. 
   
• You've understood my explanation clearly, leaving a gap or buffer of around 20mm is enough to prevent the weephole from being covered. One other method is to add a spacing timber piece so that your frame is still technically up against the wall.
   
• The pedestal feet are not required to be anchored to the ground. 
   
• Planning a provisional access for termite treatment is highly recommended. It might require you to modify your frame so that removing the decking panel will not be so involved. As long as you provide enough space for them to drill and pump the chemicals into the area you should be fine.
   
• The best way to figure out how big the gap will be in your slope is to use a builder's line. If the start of the slope is 100mm place your line at the proposed location of the bottom of the frame. Stretch the line in a straight run and tie it off to a post in the ground. Use a spirit level to make sure that the line is straight and true. You can now measure the gap that will be left under the decking frame.
   

If you have any other questions we can help with, please let us know.

Eric