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Hi All,
Newbie here and started doing small DIY stuff like making merbau planter boxes :). Now I am planning to start my decking and found this forum extremely helpful gaining the basic knowledge about decking, especially guidance from @MitchellMc in similarly low level decking threads. Here is my project details (please refer the photo attached -
- Total area - 6.3mx4m
- Clearence at Point#A:140mm, house slab sloping towards Point#B:150mm and then concrete apron sloping another 40mm, so total clearance at C is 190mm.
- Joists will be as shown in the photo and bearers just connecting end of the joists at A and C.
- Will attach the bearer to brick wall A with 10mm gap (using shims) and planning to joist hanger and L-brackets to hold the joists.
- Have granite pebbles in D, planning to use pavers + EcoDeck Bigfoot in that area to hold the joists.
- Will be using 90x45mm H3 pine for bearer and joists and 140x19mm merbau, so total height for joist + merbau is 109mm.
Questions:
1. Ground clearance in A is 31mm (140 - 109), B is 41mm (150-109) and C is 81mm (190-109). Based on this, is L-bracket a good option? If yes which L-bracket should I choose?
2. With L-backets, I probably have to use shims underneath the joists, isn't 81mm too high for using shims? what are the other options I got? Looking for options other than EcoDek foot (planning only to use it in the pebbles area D).
3. Need help with detail specs of dynabolts, L-brackets etc. suitable for the above project.
Many thanks :).
Welcome to the Bunnings Workshop community @Sujoy. It's terrific to have you join us, and many thanks for your question about constructing a deck.
For your setup, using L-brackets can be a good option where ground clearance is limited, such as Points A and B. When installing, aim to position the fasteners in the middle of the joist height, avoiding the top and bottom edges to prevent any splitting or weakening. Many DIYers go for heavy-duty galvanised brackets, which provide solid support and resist corrosion. A tip here would be to set up one joist at the required height first, then try a few L-bracket types to see what works best with your setup. Take a look at the Carinya 100 x 100 x 50 x 4.5mm Hot Dipped Galvanised Angle Bracket and Carinya 150 x 150 x 75 x 6mm Hot Dipped Galvanised Angle Bracket.
For Point C, pedestal feet would work much better here. Although they’re more of an investment, pedestal feet are highly adjustable, making them ideal for leveling decks over uneven ground or slopes. They’re sturdy and provide consistent support, especially over that height.
Regarding Dynabolts, a 70mm length should be adequate for attaching to masonry, and the thickness should match the hole in your chosen bracket. Ensure the bolts penetrate the concrete deeply enough for a secure hold.
For the brackets, try to avoid placing them near the edges of the concrete to prevent cracking.
Please let me know if you have any questions.
Mitchell
Hi @Sujoy.
That all sounds about right. In answer to your questions, those screws will be fine for attaching the brackets to the joist. You will need to predrill first. A 12 x 100mm Dynabolt would be best for the bearer attached to the bricks. Using joist hangers is the correct way to hang joists. These connector screws can be used. The joist will be supported by the joist hangers and the angle brackets. As long as they are supported adequately, there is no need for packers. These Simpson Strong-Tie 12G (5.5mm) x 50mm 316 Stainless Steel DHSD No-PreDrill Hardwood To Softwood Deck... are suitable for the decking.
Mitchell
Hello @Sujoy
Between using the 90x45 and the 100x100, I would go with the 90x45 because of the gap that it provides. My other worry is that you'll be cutting into the 100x100 post and although its treated, exposing its centre core will weaken it even with the spray coating. The more space you have under your deck means better air circulation and no trapped moisture under the deck.
Let me call on our experienced members @Nailbag and @Dave-1 for their recommendations.
If you need further assistance, please let us know.
Eric
Good Evening @Sujoy
I was just reading through the posts and I am impressed with your detail of knowledge 
You are asking the right questions.
I agree with @EricL over its wiser to have air flow then not. Because you are right on the edge of the timber touching the concrete the more you can facilitate the air flow the better for the deck long term.
I have used concrete screws instead of dynabolts for the past few years and have found them so much eaier to use and also remove. With Dynabolts you may be left with the metal sleeve if you ever decide to chnge the deck area.
Dave
Thanks @Dave-1 @EricL . It’s all the posts and suggestions by you guys helping us to learn 😊.
Based on your suggestion I have just laid the bearer with shims under to give a rough idea what I am planning. Attached photo for reference, I am getting 35mm clearance from concrete and planning to level first and screw the shims under bearer before laying it. Let me know if this looks alright.
Few other questions-
1. Should I coat underside of the bearer with bitumen?
2. should I use these screws to fix the bearer to concrete?
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