Are these two potentially-overpowered (or unintended) uses of Fabricate overpowered?

Question

Fabricate is vague about what "raw materials" are, and I've concocted multiple scenarios that seem way overpowered for a 4th-level spell. The seemingly overpowered uses are as follows:

1. As the spell has no clause about the created object being on a strong surface, you can drop hunks of stone (or anvils) on creatures and buildings, dealing up to 12d6 bludgeoning damage to creatures and/or objects underneath them, requiring only the element of surprise (and sufficient materials).
2. A passwall that can be used to bore a 20 ft. deep hole through wood walls or 5 ft. deep through stone or other materials that a) can stack and b) is permanent until filled back in.

Are these uses overpowered compared to other spells of this level, given the 10 minute casting time?

Fabricate

4th-level transmutation
Casting Time: 10 minutes
Range: 120 feet
Components: V, S
Duration: Instantaneous

You convert raw materials into products of the same material. For example, you can fabricate a wooden bridge from a clump of trees, a rope from a patch of hemp, and clothes from flax or wool.

Choose raw materials that you can see within range. You can fabricate a Large or smaller object (contained within a 10-foot cube, or eight connected 5-foot cubes), given a sufficient quantity of raw material. If you are working with metal, stone, or another mineral substance, however, the fabricated object can be no larger than Medium (contained within a single 5-foot cube). The quality of objects made by the spell is commensurate with the quality of the raw materials.

Creatures or magic items can’t be created or transmuted by this spell. You also can’t use it to create items that ordinarily require a high degree of craftsmanship, such as jewelry, weapons, glass, or armor, unless you have proficiency with the type of artisan’s tools used to craft such objects.

Answer 1

This is by no means overpowered

Thomas' answer covers the ambiguities of what counts as raw material in depth: this is not further defined and hence up to your DM.

I'd like to focus on the body of your question: if you decide that rock and wooden walls are raw materials and that you can create the object anywhere in the spell's range¹, will these uses create abusable power for a fourth level spell?

1. If you want to fabricate a heavy block of stone, it is only going to be a 5 foot cube, and will affect a single target. One time 12d6 bludgeoning is not broken for fourth level. Blight deals 8d8 of a much better damage type (necrotic), 85% as much, and sucks. A plain fireball at third level deals 8d6 fire to four² targets for a sum total of 32d6 damage, outclassing this easily. What's more, a casting time of 10 minutes makes this utterly useless in combat, and hard even to pull off in secret, as spellcasting is perceptible. So this surely is not overpowered.

2. The second exploit on wooden walls is rather useless: I have never seen a wooden wall 20 foot deep. Not even the Steading of the Hill Giant Chief had walls thicker than 5 feet. The stone version is more useful, but does exactly the amount of tunnel Stone Shape can do, only it takes ten minutes to do so rather than one action. Again this certainly is not overpowered. (It also is a question how statically stable such tunnels will be without support beams ... up to the DM.)

What is speaking for Fabricate is the flexibility. You can build stuff. You might be able to make a tunnel with it. In an extremely rare fringe case, you might dump a piece of rock on someone. That's cool. It's not broken, power-wise.

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¹ The spell does not specify where the object is created, and a DM could rule that the conversion takes place as close as possible to the raw materials. I think the example of creating a bridge from a lump of trees suggests you can create the object anywhere within Range, as you would want the bridge over a river, not in the woods. But the spell does not say "a bridge over a river".

² Using the rule on p. 249 DMG to convert areas of effect to affected targets (which I think is conservative).

Answer 2

No

A) Fabricate requires the materials and 10 minutes to cast. That means you need a large rock and 10 minutes. However, if all you need is a large rock in under 10 minutes you can probably have your fighter get one in about that time. Sure, this won’t work in desert, but Fabricate won’t work in the desert either, since you will have sand, not stone. All in all you will have just wasted a 4th level slot for something a strong party member can do for free. That doesn’t even cover the fact that you need to find a place to throw it off of and the strength to do so.

B) Passwall works without causing structural instability. If you are doing this in an underground dungeon that may be important to you.

Answer 3

It's up to the DM.

We have visited this question a few times on this stack before, in the form of "can I use fabricate on [material] to make [object]?":

• Can coins count as raw materials for Fabricate?
• Can a wizard fabricate stairs out of a castle wall?
• Can the Fabricate spell create a living bridge?

On these first two questions in particular, you will find no shortage of disagreement about what "raw materials" means, and you will find that the most well received answers on each of those first two questions come to somewhat different conclusions.

The solution here is to ask your DM, ideally, prior to the time you try to use the spell. You are much more likely to reach a favorable resolution if you talk to your DM out of game prior to using the spell than if you gamble on the DM's ruling in the heat of combat or some other high stakes, fast paced situation. Whether or not your particular ideas are overpowered is exactly the sort of thing the DM will need to consider, and discussing it with them out of game will allow the two of you to workout a compromise if the DM thinks your ideas are a little too strong.