D&D 5E Dragon's breath weapon vs wall

[Iry]

Eh, maybe?

I mean, sure, stone doesn't break easily due to heat, but thermal expansion and contraction is a serious concern with stone buildings. And dragon's breath is hot. Hotter than a flamethrower, it is more akin to the heat from a lightning strike, and that can crack stone in half.

Even with resistance a 27-hp wall would still get destroy by a 66 damage fire breath. So that seems to be working as intended?

Though lightning is quite variable, and most D&D lightning would be on the low end.

 

[Chaosmancer]

Even with resistance a 27-hp wall would still get destroy by a 66 damage fire breath. So that seems to be working as intended?

Though lightning is quite variable, and most D&D lightning would be on the low end.

True on both counts.

I was thinking IRL lightning for heat and comparing it to the damage of a lightning bolt (28) so assuming you scaled it up properly (yadda yadda yadda)

 

[Iry]

I was thinking IRL lightning for heat and comparing it to the damage of a lightning bolt (28) so assuming you scaled it up properly (yadda yadda yadda)

I personally think 2d10 for natural lightning is incredibly low. In an area of poor conductivity lightning can get 5 times hotter than the surface of the sun. I would put it closer to 10d10 with a dexterity save.

That's the same as a lava stream, would crack a 27 HP wall on average, and still allow the rare chance of a random commoner saving for 5 HP damage and surviving.

You could save the 18d10 bolts (same as magma submerging) for the really crazy ones, like what Thor did to Hel.

 

[Horwath]

object hardness was maybe best described in 3.5e and maybe worse in 5e.

One of very few issues I have with 5e.

The rules are just awful about it.

 

[BluejayJunior]

I personally think 2d10 for natural lightning is incredibly low. In an area of poor conductivity lightning can get 5 times hotter than the surface of the sun. I would put it closer to 10d10 with a dexterity save.

That's the same as a lava stream, would crack a 27 HP wall on average, and still allow the rare chance of a random commoner saving for 5 HP damage and surviving.

You could save the 18d10 bolts (same as magma submerging) for the really crazy ones, like what Thor did to Hel.

I would say that is way too high. People surviving getting hit by lightning is a pretty common occurrence. About 90% of people struck by lighting survive it. Granted, it can still mess you up in other ways, but it's rare for it to actually kill you. I think 2d10 is pretty accurate.

 

[Var]

If we're talking about real world physics a bit:

Stone starts burning/melting if it's hot enough (IRL WW2 air raid bombings did that frequently i.e. Dresden).

Fireball vs Dragon breath is different in terms of the kind of energy levels involved.
A Fireball would be less temperature damage and more force from an instantaneous explosion.
Dragonbreath from a sufficiently sized dragon would be sustained wide area application of extreme heat for a couple seconds rather than a moment. Most of the energy would be transferred by the extreme heat rather than the explosion.

So unlike a Fireball, Dragonbreath would heat up a rather sizable area of a castle wall and keeps the heat going for a bit. It wouldn't have to melt or burn a rather rigid and inflexible mineral structure under those circumstances. The stone would try to expand and has nowhere to go, parts of the wall would crack or burst and the weakened structure could crumble under its own weight.
That would be the most realistic scenario how this could pan out, at least from my point of view.

 

[Oofta]

If we're talking about real world physics a bit:

Stone starts burning/melting if it's hot enough (IRL WW2 air raid bombings did that frequently i.e. Dresden).

Fireball vs Dragon breath is different in terms of the kind of energy levels involved.
A Fireball would be less temperature damage and more force from an instantaneous explosion.
Dragonbreath from a sufficiently sized dragon would be sustained wide area application of extreme heat for a couple seconds rather than a moment. Most of the energy would be transferred by the extreme heat rather than the explosion.

So unlike a Fireball, Dragonbreath would heat up a rather sizable area of a castle wall and keeps the heat going for a bit. It wouldn't have to melt or burn a rather rigid and inflexible mineral structure under those circumstances. The stone would try to expand and has nowhere to go, parts of the wall would crack or burst and the weakened structure could crumble under its own weight.
That would be the most realistic scenario how this could pan out, at least from my point of view.

If someone is attacked by a dragon and fails their dex save, do you have them make a saving throw for their armor and personal belongings? Because the temperature required to melt stone will also melt most metals.

Because while I agree that sustained high temperatures can destroy stone walls, it takes several minutes of sustained heat at 1500 degrees Celsius (2750 Fahrenheit), not seconds. That and there is no concussive force to dragon's breath weapon ever mentioned, it's a brief (albeit intense) flash of heat.

The temperatures needed to melt rock in an instant would be so high that no organic material could survive the intensity.

But I guess without finding a friendly dragon and doing some testing we'll never know.

 

[Var]

If someone is attacked by a dragon and fails their dex save, do you have them make a saving throw for their armor and personal belongings? Because the temperature required to melt stone will also melt most metals.

Because while I agree that sustained high temperatures can destroy stone walls, it takes several minutes of sustained heat at 1500 degrees Celsius (2750 Fahrenheit), not seconds. That and there is no concussive force to dragon's breath weapon ever mentioned, it's a brief (albeit intense) flash of heat.

The temperatures needed to melt rock in an instant would be so high that no organic material could survive the intensity.

But I guess without finding a friendly dragon and doing some testing we'll never know.

You misread that a bit. While technically possible if Dragon Breath is around the hallmark of 10k °C and sustained I don't think melting or burning through a stone wall is a feasible scenario.
That was mostly just to outline how Fireballs are probably a lot less effective at breaching a castle than Dragonbreath.

Hence the "sudden temperature change cracks the stone and the wall breaks under it's own weight" (- works best when it's freezing outside at the time). Most likely still would take the Dragon several attempts to make the wall crumble layer by layer. Assuming the wall is an inner and outer shell of masonry filled with mortar and debris.

If the wall consists of 25 cubic feet solid granite blocks, then the Dragon is gonna be pretty out of breath by the time he has done cosmetic damage to the outer layer.

 

[Oofta]

You misread that a bit. While technically possible if Dragon Breath is around the hallmark of 10k °C and sustained I don't think melting or burning through a stone wall is a feasible scenario.
That was mostly just to outline how Fireballs are probably a lot less effective at breaching a castle than Dragonbreath.

Hence the "sudden temperature change cracks the stone and the wall breaks under it's own weight". Most likely still would take the Dragon several attempts to make the wall crumble layer by layer. Assuming the wall is an inner and outer shell of masonry filled with mortar and debris.

If the wall consists of 25 cubic feet solid granite blocks, then the Dragon is gonna be pretty out of breath by the time he has done cosmetic damage to the outer layer.

It may chip some stone off the facade, but it would take an incredible amount of heat to penetrate more than an inch or two. Stone in general is a pretty good insulator. Stone buildings survived a nuclear bomb, I find it hard to believe dragon's breath is more damaging.

But again, without a dragon to verify our hypothesis I'm not sure there is one true answer.

 

[aco175]

Welcome to the boards, you will find us a mostly civil bunch, have some XP to get you started.

I can see some good roleplaying if you allow the breath to eventually damage the walls. I recall some movies where something is heating up the wall and it begins to glow red, leaving the PCs to wonder how long it will hold. This may speed them up if they think that it will only hold for a few rounds, or maybe re-think trying to take a long rest behind it. I think the physical attacks of a dragon would destroy the wall before the fire would, but this all depends on how you need the game to speed along and be cool.

I could also see some sort of special stone like fire pumice that blocks or delays the breath from melting it. Another adventure right here.