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Are pedestals appropriate to build a low-level deck on a sloping concrete base?

Hello!

Planning on building a deck. Deck area is 3m x 6m on a concrete base that has a clearance of 110mm to 120mm from the ground at the point connecting the house. The concrete base then slopes away from the house and the clearance increases to ~150mm. I could only use 90x45 for the frame and joists due to height limitations. The deck boards would then level with house floor.

I am just at the researching phase and will take a while before I progress to the actual build (maybe when the weather is a bit kind).

I am considering using the pedestals to provide an even levelling across the deck. I believe I will need to use a lot of pedestals (about 60+) with the recommended spacing of 750mm running across the 6m joists.

The questions at this moment are:

- Is there a requirement to bolt the joists to the concrete using angle brackets when using the pedestals + nogging?

- Do the small pedestals have the ability to be bolted to the concrete?

- Any alternatives to prop up the frame? Using pedestals across the deck can be quite expensive.

I have attached an image to help visualise. One of the pedestals has gone rogue so just ignore that.

Thanks,

Rear deck planning 20230519.png

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Comments

MitchellMc

Welcome to the Bunnings Workshop community @SK1. It's sensational to have you join us, and many thanks for your question about constructing a deck.

It would be best to enquire with your local council regarding any requirements for securing your deck prior to construction. For the size of the deck you are creating, you're likely going to require approval, and they'll need to sign off on the construction methods you use. If you are in a high-wind area, connecting the structure to the ground would likely be a good idea.

The Eurotec 30 - 53mm Small Pro Feet Pedestals have holes in the base, allowing you to bolt them to your concrete.

Using adjustable pedestals is really a luxury as they allow a wonderful amount of adjustment, quick assembly, and allow you to build over sloping areas with ease. The downside is they can be a little pricey if you need a whole heap of them. Using multiple supports is unavoidable when you're trying to create a low-level deck that can't use a joist with a significant span.

Many of our members have successfully used angle brackets to reduce the cost of mounting joists above concrete. Your max clearance is 150mm minus the 19mm decking, leaving you with 131mm. 90mm of that will be your joist with a 41mm gap under it. You could use Carinya 100 x 100 x 50 x 4.5mm Hot Dipped Galvanised Angle Brackets Dynabolted into the concrete and then bolted to your joists.

Please let me know if you have any questions.

Mitchell

SK1

https://www.workshop.bunnings.com.au/discussion/comment/27349#Comment_27349

Hi @MitchellMc

Thank you for the input. I don't have to have such a large deck. Can start with a smaller project of a 3m*3m.

How many angle brackets would be needed to cover a 3m joist. I am assuming will need a few for the frame also.

Based on the 19mm deck board height, is the recommendation to go with Merbau over Pine?

Thanks,

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/76309#Comment_76309

Typically I'd recommend supporting a 90 x 45mm joist at least every metre @SK1. Any further than that, and they can start to get a bit bouncy. So, that would be four brackets per 3m joist.

A hardwood Merbau decking board would be considered the premium option over a softwood Pine decking board. Not only will the hardwood last longer and be less maintenance, but it looks nicer. However, if you're trying to keep to a budget, then Pine is certainly a perfectly fine option.

Mitchell

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