The damage dice of improvised weapons should increase with the size of the object being used. This table can be referenced for a rough idea coming up with damage dice for improvised weapons:

• Small one-handed items (shivs, a chair leg, etc.): 1d4
• Medium one or two handed items (a broom, a chair, etc.): 1d8
• Large bulky items (a ladder, a table, etc.): 1d12
• Extremely large objects (a carriage, a statue, etc.): 2d10

When making an attack with an improvised weapon, picking up the weapon doesn’t use your environmental interaction or free action if the item is easy to pick up quickly. What is easy to pick up is left to the DM’s discretion.

Improvised weapons that are one or more sizes smaller than you and can be held in one hand are assumed to have the thrown property with a range of 20 feet normal range and 40 feet disadvantage. Medium improvised weapons have the versatile property. Large and extremely large improvised weapons have the heavy and two handed property.

When using an improvised weapon that weighs more than half your carrying capacity, you must make a Strength(Worldshaper) check in order to make the attack roll. If the object is less than your total carrying capacity, the DC is 20. If the object weighs more than your carrying capacity, the DC increases by 5. The DC increases by 10 if the object weighs more than one and a half times your carrying capacity. Unless the DM permits, you cannot use an object that weighs more than double your carrying capacity as an improvised weapon.

Improvised weapons are typically not particularly well suited to be used as weaponry. Large and bulky objects cannot be used for whirlwind attack, and maneuvers cannot be applied to attacks made with them. Large objects also can typically only be used once before their structural integrity begins to fail under their own weight and the external forces acting upon it, making them ineffective after making a single attack with it.

• Extremely large objects may cause damage in a wider area at the DM’s discretion, forcing targets in an area around the target equal to the size of your improvised massive object to make a DC15 Dexterity saving throw or receive half of the attack’s damage.