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 @nvdshams (Naveed)

Thank you for sharing your very comprehensive plan for your deck. Let me try answering your questions.

• I am familiar with the 90x45 joist hanger, but I've not seen the 70x45 let me speak to our supplier and as soon as I have more information, I'll get back to you.
   
• I suggest having a look at this discussion - Low-level composite deck over concrete and soil by @oninpena. There is a good example of how the deck frame was routed around the column. 
   
• I recommend adding more noggins with a distance of 450mm for A1& A2 and B6 and B7. It's always a good decision to have more support for the deck rather than less.
   
• I often over-engineer my projects, hence I suggest adding a joist between B6 and B7 so that there is an extra point of support for that area. I suggest mounting this to the concrete floor with angle brackets as well. Place the noggins at 450mm as well
   
• For the Dynabolt drill bit, I suggest using a masonry drill bit that is the same size as the body of your Dynabolt. I suggest bringing the A12 Dynabolt and showing it to the tool specialist in the store. They should be able to match it to an appropriate masonry bit.
   
• I recommend using a thick angled bracket or a joist hanger to fix the joist in place. I don't recommend using the D.I.Y. Carinya bracket.
   
• The span you've placed for your footing is a bit large, this will often produce a springy deck, I recommend reducing this space to 1 meter per footing. I also suggest reducing the distance between your floor-mounted angle brackets to 1 meter as well. 
   
• Having more noggins in the deck frame act like added support and stiffen the overall construction of the frame. I would suggest a spacing of 700mm depending on the allowable space of the area.

Let me call on our experienced members @Adam_W and @DIY4Knuckleheds for their recommendations.

If you need further assistance, please let us know.

Eric

[Jewelleryrescue]

Hi @nvdshams 

That is the most incredible plan I have  ever seen for a  deck base the thought you put into it everything. I would hire you to  design my  timber projects and raised decks in a heart beat.

So please dont be mad at me when I say i would cement slab that area with  drainage for weep holes and  buy some incredible timber look alike tiles and tile that cement  top set it and forget it the rest of you life no further timber issues ever so close to ground level.

I very much respect your design and I know your fully invested by it  I would be invested to if I designed that to so you must reject my idea fully.

To me in  my area that deck base is building a cockroache and red  back  7 star hotel I have to think differently  in my area. 

[nvdshams]

Hi @Jewelleryrescue 

That is a sound advice. But we wanted to have the same continuous deck from alfresco to the garden.

You raise a really good point about pests. Although we don't have that problem in our area but you never know. Is there a preemptive measure to take before building a deck? Maybe a paint or something that pests hate?

[Jewelleryrescue]

You meantioned a  paint well as a bee keeper i used to paint my hives in  Copper naphthenate is an active ingredient used predominantly in industrial and commercial wood preservation for non-pressure (dip/brush/spray) and pressure treatments (vacuum/full cell) to protect against fungal rot, decay, termites and wood-boring insects in unfinished wood and various fabricated wood products. 

Then  paint over the top with normal acrylic paint.  This  didnt kill  bees if it became exposed It adds a bad copper taste to the wood and deters  wood chomping pests Bee keeper supplies have it. I did a bunnings search no  joy maybe at special orders desk.

The Bunnings  guys here might  have some good  extra Ideas here I just recently was attacked around the  house by a  termites  species of a medium ferocious house eating nature. I think I won its early days house  is un touched to date. yeah

So knowing all you hard work  can turn into a smorgasbord started my typing  fingers started twitching.  I spent $700+ on a early detection system add baiting stations only to be told the baiting station dosnt work with that termite speicies  What I said?

But I found the following poision product below. Pre deck add it to your soil under the deck as an option. In a  strong concentration it should last 10 years.(a bonus  it does other insects too.  afterwards perimeter re apply around your new wooden deck.  Those buggers are  all across  Australia of different kinds. Putting it under you deck especially at perimeter will keep poision away from your pets and children. Termites usually invade top 30 cm of earth not like ants.

Have you ever seen a big 30 mm winged  ant? in your area?  Thats one of them looking for a new nesting location

Hovex 1L Ultra Lo-Odour Termite Concentrate I/N: 3010162  $69.32

[nvdshams]

Hi @EricL 

Thanks for the advise. I have updated the design with 1m span and extra noggins. I have also done the following changes:

1. For timber to concrete, I am going to use Dunnings 50 x 50 x 50 x 5mm M12 Galvanised Angle Bracket with Zenith M12 x 65mm Hot Dipped Galvanised Cup Head Bolts And Nuts - 12 Pack and Zenith M12 Hot Dipped Galvanised Washer

2. For angles between joists, I will be using Dunnings 100 x 100 x 75mm M10 Galvanised Angle Bracket .

[EricL]

Hello @nvdshams

Thank you for sharing that update on your decking plans. Your plan looks excellent, just a friendly reminder not to forget to add extra floor angle bracket supports for your concrete area as well. I'm currently waiting on an update from Pryda concerning the 70 x 45 joist hangers. As soon as I have more information I'll get back to you.

Eric

[nvdshams]

Thanks for the reminder @EricL. I have updated the design. 

Just a quick question: In the very informative decking video by @MitchellMc, he connected joists using bugle screws instead of joist hangers or angles. Do they have the same strength as joist hangers?

[EricL]

Hi @nvdshams

I've received a reply from our supplier for the joist hangers, I'm afraid there are no 70x45 joist hangers. Using bugle screws is definitely an option and provides a convenient way of joining timber together. It does provide excellent holding strength. My only recommendation when using bugle screws is to make sure to drill a pilot hole to prevent splitting the timber. 

However, joist hangers provide greater shear force support to joists, as the hanger allows for both face-nailing and toe-nailing into ledger boards and rim joists. Shearing forces occur when a strong wind blows against the deck and frame, but because your deck is very low the effect will be negligible.

To add further support to the joist, I suggest putting a floor angle bracket at 100mm from the start of the joist.  

If you need further assistance, please let us know.

Eric

[jigz]

Hi @EricL , After reading details on few similar projects in this community, I have started to plan for a 10x~5.7 deck. Similar to @nvdshams scenario it will be partially over concrete patio and partially on the soil, there are also quite many weep holes in the first row of the brick from the floor.

I am intending to use 70x45 joists for concrete (100mm between concrete surface to finish level) and if possible, transition to 90x45 for the area over the soil as have larger clearance there.

Before I complete the design I have few queries if you can pls assist with:

1. can I use 50x60mm (I/N: 0294223) joist hangers to connect 70x45 joist to same size bearer/frame with 5 mm packing shims? 
2. In the post of another project, you suggested that the deck can be built past the weep holes but require to put timber buffer around them. Can you pls explain that bit further how that arrangement looks like? I noted @nvdshams had kept the space open at the weep holes so they are not obstructed by the deck frame, is that what you meant?

3. Re the pedestal feet, are they required to be fixed to the ground?

4. The Termite treatment guys few years ago had drilled 10-12 mm holes in the concrete patio every 300mm apart near perimeter of the house to inject the chemical through them, is it ok to build the deck over them? I am thinking for future access, at least laying deck boards at the perimeter such only few boards are required to be removed, e.g. making border with double or triple boards?  

5. One of the other challenge I foresee is that the concrete patio has approx. 100mm slope from one end to other towards the door out from garage, this is because the floor level in the garage is 100mm below the rest of the house floor. I think there are two possible solutions, one is to have deck finish above the sliding door track/brick by 100mm or a step down built into the deck.

Here is rough prelim plan, many corrections and improvements to be had.