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How to anchor deck joists to concrete?

Hi All,

Looking for advice on achnoring decking joists to concrete for a low level deck. My joists will be 140mm x 45mm with 140 x 19mm Merbau decking. Overall clearance from conreate to top of deck is 180mm.

Current plan is to use-

Carinya Heavy Duty 75 x 75 x 40 x 3.5mm Zinc Plated Reinforcing Angle Bracket

Dynabolt these to the concrete with - one - Ramset 10 x 75mm DynaBolt Plus Hex Nut Bolt (do i need to use something different on the perimieter of the concrete?)

Question 1 - what should I use to fix the Joist to the Angle bracket?

Question 2 - Is flashing or Protectadeck joist protection required/overkill?

Question 3 - This will be a picture frame deck, for the two ends that require a second joist with the offcuts, what screws should be used to fix these together, or do I need to run a bolt through?

Question 4 - where are washers required?

Question 5 - Is an SDS Hammer drill best for getting through conrete, and is a impact wrench best for tightning dynabolts?

Question 6 - If I'm using angle brackets to fix the joists to the conrete, are noggins required?

Thanks in advance

Jesses6

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Comments

MitchellMc

Hi @JesseS6,

If your fixings are less than 100mm from the edge of the concrete, consider switching to Ankascrews instead of Dynabolts, as they’re less likely to crack the concrete edge.

Adding protection like Protectadeck to your joists isn’t overkill—it helps prevent water from sitting on top of them and is a great way to extend the life of your structure.

For the picture frame ends, you can use landscape screws or large bugle screws to join the timbers. You’ll likely need spacers between the two lengths to increase the width and provide a better fixing area for the picture frame and board ends.

Washers aren’t typically used in deck construction unless you’re using bolts.

A SDS hammer drill is the best option for drilling into concrete, as it’s much faster and more effective than a standard drill with a hammer function.

For tightening Dynabolts, an impact wrench would work well, but a manual socket set can also do the job.

Lastly, noggins should be used to improve lateral support and prevent joists from twisting.

Please let me know if you have any questions.

Mitchell

JesseS6

https://www.workshop.bunnings.com.au/discussion/comment/49077#Comment_49077

Thanks @MitchellMc ,

Where there is bearers under the joists, (for example when a deck is over concrete and soil) how should the joists be fixed to the bearers? is a Framing gun with a nail angled in on either side of the joist? (into the bearer)

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/86623#Comment_86623

Joist straps would typically be used @JesseS6. Skew nailing could be used, but with both fixing methods, noggins should be installed.

Mitchell

JesseS6

https://www.workshop.bunnings.com.au/discussion/comment/108711#Comment_108711

Thanks @MitchellMc , sorry for all the questions.

For the angle brackets, when fixing it to a joist, what should be used? a bolt through the joist or is a some sort of timber screw/coach screw?

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/121665#Comment_121665

Pryda Timber Connector Nails 35 x 3.15mm and used for those brackets @JesseS6.

Mitchell

JesseS6

https://www.workshop.bunnings.com.au/discussion/comment/129823#Comment_129823

@MitchellMc nails for the angle bracket that connects the joist to concrete?
I would of thought screws would be needed.

JacobZ

Hi @JesseS6,

I think @MitchellMc thought you were still referring to the joist straps which would use connector nails.

To connect the angle brackets to your joists, you should use bolts rather than screws. You should use the thickest galvanised bolt that will fit through the predrilled holes in the bracket. These Zenith M8 x 70mm Hot Dipped Galvanised Cup Head Bolt And Nuts should work, but you'll have to double-check in person to confirm.

Let me know if you have any further questions, I'm happy to help.

Jacob

JesseS6

https://www.workshop.bunnings.com.au/discussion/comment/49077#Comment_49077

@MitchellMc Hi Mitch,

Just a quick query, for the substructure, I'm using 90x45mm joists, can a frameing gun be used for fixing the joists and noggins?

The joists are also sitting on pedestals, is there a recommended screw for fixing these the pedestal to the joist?

EricL

https://www.workshop.bunnings.com.au/discussion/comment/88968#Comment_88968

Hello @JesseS6

While framing nail guns are suitable for certain parts of deck construction, such as framing, joists, and trusses, they are generally not recommended for the entire deck frame. For the main frame, screws are often preferred over nails due to their superior holding power and ability to resist loosening over time. For a superior finish I would endorse using screws for the entire assembly. As for fixing the pedestal to the joist, I suggest using galvanized or coated screws at least 10g or bigger if the pedestal fittings can accommodate it. A screw length of 30 to 40mm should be sufficient.

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

Eric

JesseS6

https://www.workshop.bunnings.com.au/discussion/comment/110238#Comment_110238

@EricL thanks! Very helpful.

What screws would you suggest for the subframe? (noggins etc) it's all 90x45mm

EricL

https://www.workshop.bunnings.com.au/discussion/comment/122482#Comment_122482

Hello @JesseS6

I suggest using Titan 14G x 125mm CL3 Gal Bugle Batten Screw - 100 Pack just like its shown in this guide - How to build a deck by @MitchellMc. For the noggins you can use the same screw or a smaller gauge but nothing smaller than a 10g screw. Remember to drill pilot holes for all the screws to prevent splitting the timber.

If you need further assistance, please let us know.

Eric

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