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How to build a low-level deck with flush bearers instead of pedestals?

nalakas90

Hi,
I’m planning to build a low-profile deck in my alfresco area, which doesn’t have enough clearance to have joists supported on top of bearers. In my original plan, all the joists were going to be supported by joist pedestals fixed directly to the concrete. They were spaced at 1.1m (3 pedestals per joist), requiring 34 pedestals in total.
Deck size is 4.2m x 6.4m
joist size is 90x45mm.

I recently watched a video of a deck built without using that many pedestals. Instead of putting a pedestal under every joist, the bearers fixed to the frame on the same single level (flush with the joists). These bearers are supported by far fewer pedestals than what I originally planned.

Below is what I am now planning to do: use stronger timber (140x45mm) for the bearers, supported by pedestals spaced at 1.4m. For the joists, I’ll still use the same 90x45mm timber as before.

I feel like this will be much easier to build than my previous plan, especially considering that only the bearers need to be leveled across the deck, and the joists will naturally follow that level.

I would like to hear your ideas about my new plan and whether it will be just as solid as my first one.

i followed this span table to determine the spacing of the bearers and the pedestals
https://www.workshop.bunnings.com.au/discussion/246961/how-to-understand-deck-span-tables?utm_source=community-search&utm_medium=organic-search&utm_term=undestand+the+span+table

P.S. The new plan draft is not to actual shape and size; it's just to show how I plan to lay the timber

Thanks.

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EricL

Hello @nalakas90

Thank you for your question about your decking project. Before moving ahead, it may be worth checking with your local council regarding any requirements for low-level decks of this size. Although the deck is considered low-level, it exceeds 10m2, and council regulations can vary. Checking beforehand can help ensure everything is compliant and avoid any surprises later on. Depending on the specific requirements in your area, a permit and/or engineering plans may be needed for the project.

Personally, I tend to over engineer my own projects, in this instance, I would suggest adding an extra bearer so that the span of the 90x45 will not be so large. I would also add noggings between the 90x45's to stiffen the frame.

Let me call on our experienced members @Dave-1, @Nailbag, @Remarka6le, @TedBear, @JoeAzza and @DIY4Knuckleheds for their recommendations.

If you need further assistance, please let us know.

Eric

Dave-1

Good Morning @nalakas90

I also tend to over engineer things I build. Mainly to stop any issues down the track and in this case bounciness or springiness of your deck. The further apart the supports the more that "feeling" will creep in. I think along the lines "for the price of an extra few supports id rather sleep better knowing its not an issue"

That first picture where you have the rear support sitting on pavers? I am not keen on any decking timber sitting on pavers as it WILL lead to probelms down the track. Imagine having to replace that length after your deck is installed, now that would be a pain.

Looking at your photos again, both outer rails do not seem to have supports? Are you planning to attach these to barge boards type deal?

Dave

nalakas90

Hi @Dave-1, @EricL,

Thank you so much for your feedback.

The plan shown in the first two images has already been approved by the council.

Support for the outer rails (coloured brown) is provided by attaching them to the wall.

For more context, I have attached an image showing how this will sit with my alfresco area. The long 13 m × 0.95 m strip has concrete paving, and the rest of the area has compacted rubble.

Could I ask both @EricL and @Dave-1 if I follow the new method (having the bearers flush level with the joists) for the original design, how many 140×45 bearers would you recommend across the 6.4 m × 4.4 m deck?

Dave-1

Good Morning @nalakas90

I would follow @EricL's adviceand add an extra bearer. I still have concerns about fixing to the side of the wall. I prefer freestanding options instead.

One thing I would add in as you say gravel will cover a lot of the area is to make sure you provide adequate ventilation underneath the deck to help stop the timber rotting as well as make sure you have drainage installed before the deck goes in.

Dave

nalakas90

Thank you for your advice @Dave-1,

May i ask you why you would prefer the free standing option over fixing it to the wall?

The whole deck has a roof over it (except the long trip on the paving) is it because rainwater flowing in between deck and the wall? Actually the beam will be fixed on not to the bricks but to the concrete footing

Dave-1

Morning @nalakas90

I dont like the idea of having an immovable object (The wall) being used as a fixing point for something that may have some movement (The deck)

The structure (The deck) should be able to stand alone and not need strengthening via a fixed beam.

The wall that you are referring to is a retaining wall? If so then definitely it will move over time. If your deck is hard up against it then all the lateral stress will come out somewhere. Think concertinaing…

When I built my two decks I have made sure they are stand alone, I dont want added stresses to a fence line/retaining wall or the house itself. Just lowering future instances of issues mainly.

Dave

EricL

Hello @nalakas90

I'm in total agreement with @Dave-1's suggestion. Add one more bearer and make the deck frame free standing so that your walls will not bear any stress. My only other suggestion is to install https://www.bunnings.com.au/pryda-joist-hanger-to-suit-45-x-90mm_p0294207 and noggings to the frame.

Eric

nalakas90

thank you very much for your advices, @Dave-1 and @EricL.

I think now i know how to change my plan but still to have a solid deck.

i’ll share my project once finish it.

thanks again for your support 😊

Nalaka

Dave-1

Good Evening @nalakas90

:) Looking forward to seeing the project, please take plenty of photos (never too many) We are always around to think of ways things could be done. Its your project so yep you can listen to us but you are the one building it :) And the one that will stand back and say "Ohhh yeah" when you finish it!

Dave

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