Hi @livv_33,
A warm welcome to the Bunnings Workshop community and thank you for your question.
Your choice of materials will depend on a couple of different things.
Are you looking for the picnic table to last for a long time and will it be exposed to the weather? Or are you looking for something cheap that will be used maybe once or twice?
Is the table going to be low to the ground without any seats? Or would you like to use it as both seating and a table?
If cheap is the main thing, and you aren't planning on building seats, then you could make a basic table out of 90 x 22mm H3 Treated Pine Decking, which is treated for exposure to weathering while still being relatively strong and relatively cheap.
If you would like it to be usable as seating as well as a table, you will need to use H3 framing to create a supporting frame for your decking timber as decking won't be strong enough to support people without the framing.
Let me know what you think and if you have further questions, please don't hesitate to ask.
Jacob
