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Low-level deck with overhang

Great community here. I've been reading a lot about building a low level deck. But still have a few specific questions just to make sure before I buy the materials.

I plan to build a low level decking on top of my concrete floor and will span around 1.8m across the grassy part to the right of the photo.

I plan to use 70x35mm for the joist as it has enough height to just level with the floor of the house after decking is installed.

Questions:

1. for the 1.8m joist that will span the right side, do I need to double up the 70x35mm joist? or single is ok?

2. for the bearer, I'm planning to use 140 x 45 mm how far from the concrete floor can I position it? Can I have just one bearer positioned 1.8m from the concrete floor? or do I need to put 2 bearers 0.9m apart?

3. Joist spacing should be 450mm? is this the same if I will use pine?

Thank you!

Community manager's note: Check out How to build a low-level deck for expert advice.

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Comments

MitchellMc

Welcome to the Bunnings Workshop community @archerwinmakes. It's fabulous to have you join us and great to hear about your deck project.

Could we please know the height from the concrete slab to the house's floor and the overall dimensions for the deck? I can then recommend timber sizes for you to use and will provide a plan of how you need to set out your decks bearers and joists.

Mitchell

archerwinmakes

https://www.workshop.bunnings.com.au/discussion/comment/11625#Comment_11625

Hi Mitchel,

Thank you.

The concrete slab is 145mm lower than the house floor. The soil is around 80mm lower than the top of the concrete slab.

The total area is 7.34 m x 5.20 m. Area in concrete is 7.34 m x 3.20 m and area in soil is 7.34 x 2.0 m.

Thank you for your help.

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/68260#Comment_68260

Hi @archerwinmakes,

I'd recommend using Treated Pine Outdoor Timber Framing 90 x 45mm for the joists. The 90mm joist plus 19mm decking will then allow 36mm for airflow and drainage. You'll need two supports over the soil area, one being the midpoint. It would be a great idea to lower that soil and lay some drainage matting and gravel over the area.

I've included a basic diagram below.

Mitchell

archerwinmakes

https://www.workshop.bunnings.com.au/discussion/comment/97026#Comment_97026

Thanks Mitchell,

How many supports do i need for the bearers? Also, what bearers do I need to use?

Do I need to put noggins on the joist that are on the concrete?

For the joist sitting on top of the concrete, do I need to lift them up a bit or can they stay direct on the concrete? The concrete part is fully roofed and graded so water flows out from the concrete floor. thanks

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/115144#Comment_115144

Hi @archerwinmakes,

You don't have enough room over the soil area to use a traditional joist over bearer layout. It will just be a continuation of your joists on the concrete, which then have noggins in between them. Supporting every second joist should be sufficient, but I'd encourage you to check the relevant timber span tables and construction codes.

You don't need to put noggings between the joists over the concrete as they with be Dynabolted to the concrete with brackets. They need to be lifted to allow airflow and drainage.

Mitchell

archerwinmakes

https://www.workshop.bunnings.com.au/discussion/comment/125406#Comment_125406

What's the recommended amount of lift for the joist? and how many brackets per joist do you recommend?

Also, I'm willing to remove soil to allow for bearers. What is the recommended size for the bearers to use so I can plan how much soil to remove.

thanks a lot.

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/132307#Comment_132307

@archerwinmakes,

You'd need at least 10mm, but as you'll be using 90mm joists and 19mm boards, it makes sense to lift them 36mm for a deck that is flush with the door sill. Bearers generally start a 140 x 45mm, so you would need 140 + 90 + adequate space between the bearer and soil. You'd be looking at around 330mm below the height of the concrete. Generally, low-level decks don't utilise a joist over bearer system. You should find this article helpful: How to build a low-level deck by @Adam_W.

Mitchell

archerwinmakes

https://www.workshop.bunnings.com.au/discussion/comment/136505#Comment_136505

@MitchellMc Thanks for your replies.

I have a product question for this build.

I think I'm going with your 1st suggestion on supports directly to the joist.

I plan to to follow @Adam_W suggestion to dig the holes, build up the frame, level it and concrete in the support.

Questions:

How big does the hole need to be?

What type of stirrups do I need to use?

Is the Australian Builders quick set concrete ok for the job?

Also, for lifting up the joists over concrete, how many supports (L-brackets) do I need per joist over the concrete to ensure it's stable?

So many questions... thanks!

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/139405#Comment_139405

@archerwinmakes,

Footer sizes are determined by the type of soil you have in your location, and your local council might be of some assistance in determining this. As a general rule of thumb, a 300 x 300 x 450mm hole would be a good starting point.

You can use anchor stirrups, and the product you use will be determined by how much of the soil you intend to remove. Australian Builders 20kg Quick Set Concrete would be suitable for setting the stirrups in place.

Since you'll be lifting the joist 36mm, I'd suggest the Builders Edge Pedestal Foot Smallfoot 35 - 60mm would be perfect to use instead of L brackets. You'd place them every meter along the joist. Alternatively, a bracket similar to Carinya 100 x 100 x 50 x 4.5mm Hot Dipped Galvanised Angle Bracket would be suitable.

Mitchell

archerwinmakes

https://www.workshop.bunnings.com.au/discussion/comment/141341#Comment_141341

hi @MitchellMc ,

a bit of change of plans... I was reading about steal framed decks and would like your advice on the appropriate steel equivalent of a 140x90 bearer?

As mentioned above, part of my deck (around 2m) will be over soil. I don't want to scrape the top soil to get the 330mm clearance... As of now the clearance is already 100-150mm below the concrete level.

I was thinking a steel bearer will allow me to use a shorter bearer but still has the strength of a 140mm timber.. thanks

EricL

https://www.workshop.bunnings.com.au/discussion/comment/142893#Comment_142893

Hello @archerwinmakes

For us to get that information, you will have to create a new framing plan just for that section over the soil. The Steel-Deck Provider will then design and quote a frame for that area. In essence, you will be building a timber frame for the part that is over the concrete area and a steel frame that's over the soil. I suggest drawing a basic plan and bringing it to the Special Orders Desk of your local store and asking them for a quote using the Steel Deck system. Include all the relevant information needed such as height, length, width, and condition of the area. It's recommended that you include a photo so that the engineer designing it will have a better idea of where it's being installed.

They will then send all the information that you provided to Steel-Deck. Once they finish the design, Steel-Deck will send the quote back to your store and then they will pass the quote back to you. The quote will include the price and information about the steel frame.

Please keep us updated with your progress, we look forward to seeing the start of your decking build.

Eric

archerwinmakes

https://www.workshop.bunnings.com.au/discussion/comment/143892#Comment_143892

Hi Eric,

I'm not planning to make the whole frame made of steel. Just the bearer. any recommendation that can replace the 140 x 45 mm bearer?

thanks

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/144670#Comment_144670

You'll likely need to find the information from the steel beam manufacturer @archerwinmakes. Was there a particular product you had seen? We really only deal with Steel-Deck that produces frames and not singular beams.

I'm keen to assist further once we know what product you are thinking of using.

Mitchell

archerwinmakes

https://www.workshop.bunnings.com.au/discussion/comment/144670#Comment_144670

@MitchellMc For the joist to be installed over concrete (that has some fall) how do you ensure that the joists are level to each other without using a ledger board?

I'm thinking of running a string line that's level and using that as a guide to align the top of the joists. Is that a good strategy or is there a better way?

The length is 7.2m and i'll be using around 19 joists accross.

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/145241#Comment_145241

Hi @archerwinmakes,

A level string line is likely your best option over 7.2m. For smaller decks, you can place a stick of timber across the joists and use a level on top of it. You should find one of these Craftright Level Line Surface Sets useful.

Mitchell

archerwinmakes

I forgot to update this post with the finished deck.

My father & I completed the decking in about 3 weekends.

MitchellMc

Awesome results @archerwinmakes! I trust you're exceptionally happy with the finished project.

Well done and many thanks for sharing.

Mitchell

archerwinmakes

https://www.workshop.bunnings.com.au/discussion/comment/29777#Comment_29777

Yes. Very happy with the results! Thanks for all the help.

EricL

https://www.workshop.bunnings.com.au/discussion/comment/77403#Comment_77403

Hi @archerwinmakes

Thank you so much for the photo updates. The deck looks marvellous and the colour you've chosen is just gorgeous, can you please tell us the name of the colour you chose for the decking panel? What did you use for posts in the soil section of your deck? How long did the entire project take?

Again, thank you for sharing such a wonderful decking project.

Eric

archerwinmakes

https://www.workshop.bunnings.com.au/discussion/comment/102699#Comment_102699

Hi EricL,

I used Ekodeck Plus Designer Backbeach for the decking boards and Ekodeck Plus Designer Backbeach Edge for the edge boards fixed with Concealed Fix 3mm Quickfix for timber joists.

I used Pine Structural Treated H3 140 x 45mm as bearers for the part above the soil. Joists are Pine Structural Treated H3 90 x 45mm.

When over concrete area, joists were supported above concrete level with Bracket Angle HD Dunnings 90x150x75x6mm M12.

For the posts in the soil section, I used Post Anchor HD Galv Pryda buried in concrete and Cypress Post Sawn F7 100 x 100mm as posts.

I also painted all timber outside the roof boundary with Bondall 4L Inground Timber Protector.

All in all it took around 3-4 weeks, with 2 people working mostly on the weekends.

EricL

https://www.workshop.bunnings.com.au/discussion/comment/118359#Comment_118359

Hi @archerwinmakes

Thanks for that extra update. I'm sure our members will find this information very handy should they decide to build a similar project.

Again, thanks for sharing such a wonderful project.

Eric

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