What support for odd-shaped deck?

DIY2025

Area layout

Hi first time poster long time reader.

I am working on a plan for a deck build. I am a reasonably skill DIY'er and am confident in the execution but before I commit I was hoping to get some feedback on my plans in general and some advice specifically on the post locations. The site is to the side of the house between the house and boundary fence.

We have a odd shaped area for the deck. The ground to deck level clearance at the high end is 100mm with a fall of 300mm front to back (top to bottom in the image) I am going to excavate the area to increase the clearance as much as possible but am planning on hanging joist in the same plane as the bearers to reduce the excavation. The plan is timber frame with modwood boards. Not set on orientation however was planning on bearers and boards running along the longer length (with breaker boards) with the joists perpendicular.

I am planning on using stirrups set in concrete footings to reduce the chance of moisture being a problem (its the side of the house and quite a shaded area) Due to the clearance limitation I am intending on using 90 x 45 timer for the framing and doubling up on the bearers. I am very much an "over engineerer" when building so the preference is to add extra support when/where needed.

Due to the odd shape is someone able to help with footing locations. Not locked into a span so happy for the footing to accomodate where needed. Happy to provide any more infromation to help.

EricL

Hello @DIY2025 

Welcome to the Bunnings Workshop community. It's sensational to have you join us and thanks for sharing your question about your decking project.

I suggest having a quick look at these guides - How to build a low-level deck by @Adam_W and How to build a deck by @MitchellMc. These guides will give you a very good idea of what to take into consideration when planning your decking frame. I also recommend having a look at this featured project - Low-level composite deck over concrete and soil by @oninpena. It's an excellent example of how to design a single level decking frame on a slope. 

I also suggest reading - How to understand deck span tables and How do you read span tables? by @dowd_hardware. This will help with determining the footing for your deck. I propose laying out the bearers and joist for your frame (depending on the type of frame you'll be designing) and then sharing it with the community along with any questions you might have about your design. Once we see your decking frame, we can then make recommendations in regards to footing positions.  

Please note due to the size of your deck, I suggest checking the rules and regulations of your local council in regards to deck size and low-level deck distance from fence. Since your deck is larger than 10 square meters a permit might be required.

Here is a link for ideas and inspiration: Top 10 most popular deck projects 

I also suggest looking at the Bunnings deck building guide:

• How to plan out your deck
   
• How to set out a deck
   
• How to install stumps
   
• How to install bearers
   
• How to install joists
   
• How to lay decking
   
• How to add a step to your deck.

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

Eric