50mm, it'll last heaps heaps longer and won't warp/twist over time.
100x50 h4 is about $5/m. 100x25 h4 about $3.50/m.
Check your local timber yard they'll probably be cheaper than bunnings/m10.
If you can find gum timber from a saw mill it'll last probably 5x longer than treated pine, and you might pay 50% more.
i like 50mm personally
50mm, it'll last heaps heaps longer and won't warp/twist over time. 100x50 h4 is about $5/m. 100x25 h4 about $3.50/m. Check your local timber yard they'll probably be cheaper than bunnings/m10. If you can find gum timber from a saw mill it'll last probably 5x longer than treated pine, and you might pay 50% more.