Can you move through an object's space according to RAW?

Question

This looks like a trivial question, but I didn't find a sound answer in the rules.

The rules explicitly allows you to move through a nonhostile creature's space:

You can move through a nonhostile creature's space.
(Basic Rules, "Moving Around Other Creatures")

The rules also allow you to move through a creature two sizes larger or smaller:

you can move through a hostile creature's space only if the creature is at least two sizes larger or smaller than you

Whether a creature is a friend or an enemy, you can't willingly end your move in its space. But what about objects? They have the same size categories as creatures do. Does an object's size category directly affect what area this object can block?

Can you move through a Large wooden box's space? Can you willingly end your move in a Medium cauldron's space?

Inspired by this question and its comments, which apparently assumes an object Size category works the same way as a creature Size:

If the answer is "it doesn't occupy any space," then it doesn't have a meaningful size on the grid.

Size is also a defined game term.

I think it's clear to anyone that plays the game.

Answer 1

Maybe

You had stated that you couldn't find a sound answer in the rules to the question of whether you could move through an object's space and to the best of my knowledge as someone that's read the DMG cover to cover, there isn't one to that specific issue because there can't be one that would cover absolutely everything.

Can you move through the space of a Large wooden box? Maybe yes if the box is empty and has holes of adequate size; maybe no if the box is full of watermelons; maybe yes if the box is solid but you can make a strength check to Kool-Aid man through the wall. They're all large boxes, but the manner by which they're handled for the sake of moving through their space depends on the circumstances. Hence the general catchall of rulings, not rules which is helpful for adjudicating the endless situations one can come up with for characters interacting with objects.

Generally speaking, the rules of 5e aren't suitable for providing concrete direction on every type of interaction a character can have with an object. To quote the initial Sage Advice column:

The DM is key. Many unexpected things can happen in a D&D campaign, and no set of rules could reasonably account for every contingency. If the rules tried to do so, the game would become unplayable. An alternative would be for the rules to severely limit what characters can do, which would be counter to the open-endedness of D&D. The direction we chose for the current edition was to lay a foundation of rules that a DM could build on, and we embraced the DM’s role as the bridge between the things the rules address and the things they don’t.

To that end, the DM will have to make a call.

Answer 2

Objects and creatures take up space differently.

You can't apply anything about moving through a creature's space to moving past objects. Creatures occupy their space. As such, a gnome and a goliath occupy the same space. This is clearly different from how a a gnome-sized mannequin and a goliath-size mannequen would affect movement in a 5 x 5 foot space.

Occupying Space is a game mechanic to control movement, primarily in combat. Objects are just things in the way.

So, it's up to the DM to decide.

I would recommend some type of scale where:

1. Objects start to create difficult terrain at some point, but that penalty can be overcome by an athletics or acrobatics check.
2. Object are difficult terrain without the ability to overcome the penalty. This would encompass squeezing rules.
3. Objects block the way and characters must use climb, jump, break them down, etc. to get past them.

Oh, and don't forget the Rule of Cool when dealing with movement around obstacles. This is a good chance for players to be creative about how they overcome the obstacles.

Answer 3

Moving through object: it depends.

I (mis-used) related rules for a chase through a busy marketplace based on overland travel/difficult terrain - halving movement speed for passing through obstacles (aka heavy terrain):

1. My players saw a pickpocket-spiel in a marketplace - the thiefs did the ususal 3 on 1: 1 runs into the mark and is apolegetic about it, helping it back up and patting them down, etc. Another pickpockets the mark while it is beign fussed over by the first and passes the object to a third which casually walks away.

2. Normally the marketplace is a big open place with a few fixed stalls (smithy, butcher, ...) for everyday-sales. On market day though plenty of smaller tents, carts & carriages as well as arrangements of baskets/boxes with goods in them are stuffed between the fixed stalls - only small alleys are left.

3. Players were warned about pickpockets, keeping track of their surroundings while equipping for a travel ahead. They picked up on what some thiefs did, detected the object-pass and two of them gave chase while the others tried to "arrest" the bumper and the actual pickpocket which quickly escalated into a brawl.

I opted to ignore other shoppers (thiefs and players needed to pass by them) and borrrowed/simplified from special movement:

Staying in the alleys was normal movement, passing through occupied spaces (basket/boxes, carts/carriages, tents) took 100% movement penalty (5->10).

The fleeing thief mostly used alleys and the fixed stalls/tents to try to break sight and get lost.

However, the players started moving through occupied fields and had options to avoid the doubling of movement costs:

• baskets/boxes could be passed through or vaulted over (Acrobatics/Dex: passing through, Athletics/Str: jump)
• carts/carriages could only be vaulted (Athletics/Str: jump)

Missing a dex check just meant it cost the original 10 movement to pass, missing a jump cost another 5 movement on top (15 instead of 10) to get back up.

It was quite a bit of dice rolling (due to the time constraints) - eventually they caught up and arrested the thief.

For a non-time constraint situation I would simply double the movement costs and be done with it.

Similar movement impeding effects (terrain wise) are applied through spells, namely:

• Spike growth (2nd) - difficult terrain + damage
• Plant growth (3rd) - quadrupling movement costs

which could also give you some help about how to rule it.

Answer 4

RAW, objects can occupy spaces.

Many game features permit movement into, or appearance in, an unoccupied space, while forbidding them to occupied spaces. Unfortunately, what makes a space 'occupied' is never defined.

Typically a space is considered occupied when it has a creature controlling it, but creatures are not the only things that can occupy spaces; objects can as well.

We know this from the text of dimension door (emphasis mine):

If you would arrive in a place already occupied by an object or a creature, you and any creature traveling with you each take 4d6 force damage, and the spell fails to teleport you.

It is also apparent in the description of a figurine of wondrous power (emphases mine):

If the space where the creature would appear is occupied by other creatures or objects, or if there isn't enough space for the creature, the figurine doesn't become a creature.

RAI, larger objects occupy space - but we are not told how large they need to be to do so

In response to a question about whether a spiritual weapon denies use of a space to creatures, Jeremy Crawford wrote:

A spiritual weapon doesn't pass through walls. It also doesn't occupy its space; it's not a creature, and it's not described as being large enough to fill its space.

Now, a spiritual weapon is not an object, it is a spell effect - but we can take Crawford's general point that in order to occupy a space, a thing needs to be large enough to fill the space (or, like a creature, be actively controlling the space to deny entry).

However, what we are not told is how large is large enough. We might guess that it would take a Medium-sized object to fill a Medium space (5' x 5', the space controlled by a Medium creature). In the DMG's description of Objects we are given chests and lutes as examples of Small objects, and barrels and chandeliers as examples of Medium objects. A large and ornate chandelier, if for some reason on the floor, could easily prevent a creature from moving through the space. A barrel, which we can take to be the kind of barrel that is significantly larger than a chest and thus probably a hogshead or larger, might be difficult terrain and cover on the small end, or prevent movement through the space on the large end.

DMs decide what is difficult and what is impassable

Thus there is some line between objects making spaces harder to pass through (difficult terrain) and them being large enough to fill their space, denying entry. That line is for the DM to determine. The PHB gives guidance in terms of what might be considered difficult, but passable, terrain and many of the examples have to do with negotiating objects as obstacles (emphases mine):

Boulder-strewn caverns, briar-choked forests, treacherous staircases--the setting of a typical fight contains difficult terrain...Low furniture, rubble, undergrowth, steep stairs, snow, and shallow bogs are examples of difficult terrain.

Answer 5

Up to the DM, but the squeezing rules can provide a benchmark in some cases

As quoted in Kirt's answer, both dimension door and figurine of wondrous power have text that makes it clear an object can occupy space, but we have no explicit guidance on how large or massive they need to be to do so. So this will in the end be up to the DM to decide.

For making that decision, it may be useful to consider the squeezing rules (PHB, p. 192)

A creature can squeeze through a space that is large enough for a creature one size smaller than it. Thus, a Large creature can squeeze through a passage that's only 5 feet wide.

This can provide some useful guidance. For example, a small creature can squeeze into a space that is only 2.5x2.5 feet large. So, if an object occupied less than 3/4 of a 5x5 foot square, that space could be entered by a small creature. You could use this to inform your decision and say, the object is not large enough to occupy the space for a small creature, but it is for a medium or larger creature.

Any object in the way that makes the space smaller than what you normally need (e.g. 5x5 feet free space for small creature) would require the creature to squeeze, and as squeezing costs extra movement, could incure a movement penalty, even if you enter.

Unfortunately, the squeezing rules are broken for medium creatures, as small creatures occupy just as much space as them, so a medium creature cannot usefully squeeze at all, or would need to sequeeze all the time, which of course is nonsense. So for this most common case, they unfortunately do not help much.