What can I break and how long does it take to break it?
Solution 1:
This is an accurate list of things you can destroy and the effort you need. I didn't tried personally to destroy all the things listed, but many that I tried confirm those numbers.
Pratically is important to remember that you can destroy all except pillars, ceilings and foundations.
Credits to user Juper0 / Source
Wood
Wood Shelter: 400 Hits - Metal Hatchet, 167 Hits - Pickaxe, 11-12 - Grenades, 1-2 Charges - C4
Wood Wall: 11-12 - Grenades, 2 - Charges C4
Wood Pillar: Only by decay
Wood Stairs: 54 Hits - Metal Hatchet, 23 Hits - Pickaxe, 11 - Grenades, 1 Charge - C4
Wood Ramp: 84 Hits - Pickaxe, 10 - Grenades, 1 Charge - C4
Wood Ceiling: Only by decay
Wood Foundation: Only by decay
Wood Window: 11-12 - Grenades, 1 Charge
Wood Window w/ Bars: 2 Charges - C4
Wood Doorway: 11-12 - Grenades, 1-2 Charges - C4
Wood Doorway w/Door Attached: 2 Charges - C4
Wood Door: 200 Hits - Metal Hatchet, 84 Hits - Pickaxe, 6 - Grenades, 1 Charge - C4
Wood Gateway: 5 Charges - C4
Wood Gate: 120 Hits - Pickaxe, 32 - Grenades, 3 Charges - C4
Metal
Metal Wall: 4 Charges - C4
Metal Pillar: Only by decay
Metal Stairs: 1 Charge - C4
Metal Ramp: 1 Charge - C4
Metal Ceiling: Only by decay
Metal Foundation: Only by decay
Metal Window: 3 Charges - C4
Metal Window w/Bars: 3 Charges - C4
Metal Doorway: 2 Charges - C4
Metal Doorway w/Door Attached: 3 Charges - C4
Metal Door: 11 - Grenades, 2 Charges - C4 (Metal Doors cannot be damaged by melee weapons or guns. Only through explosives.)
Objects
Wood Barricade: 17 Hits - Pickaxe, 2 Charges - C4
Spike Wall: 25 Hits - Pickaxe, 1 Charge - C4
Large Spike Wall: 100 Hits - Pickaxe, 2 Charges - C4
Small Stash: 5 Hits - Rock, 7 Hits - Stone Hatchet, 4 Hits - Metal Hatchet, 2 Hits - Pickaxe
Small Wood Storage Box: 34 Hits - Stone Hatchet, 20 Hits - Metal Hatchet, 9 Hits - Pickaxe, 1 Charge - C4
Large Wood Storage Box: 67 Hits - Stone Hatchet, 40 Hits - Metal Hatchet, 17 Hits - Pickaxe, 3 Charges - C4
Furnace: 34 Hits - Stone Hatchet, 20 Hits - Metal Hatchet, 9 Hits - Pickaxe, 2 Charges - C4
Workbench: 67 Hits - Stone Hatchet, 40 Hits - Metal Hatchet, 17 Hits - Pickaxe, 3 Charges - C4
Camp Fire: 34 Hits - Stone Hatchet, 20 Hits - Metal Hatchet, 9 Hits - Pickaxe, 1 Charge - C4
Sleeping Bag: 34 Hits - Stone Hatchet, 20 Hits - Metal Hatchet, 9 Hits - Pickaxe, 1 Charge - C4
Solution 2:
The playrust wiki (http://playrustwiki.com/wiki/List_of_things_to_Craft) lists all the items and what can be broke on every individual page from that list. For example, for the wood door :
Wood Doors are destructable - they can be taken down when it has been hit 200 times with a rock or 80 times with a pick axe.
The wiki will also tell if sometimes item can't be destroyed. However, they might despawn under certain conditions.