In the book, it is mentioned :

Blasts in a Confined Space

When a grenade detonates in a confined space, such as a hallway or room, the gamemaster must first determine whether any barriers (usually walls) stood firm against the explosion. Consult the Destroying Barriers rules (p. 197). If the walls or doors hold up, the blast is channeled. Otherwise, determine blast effects normally. If the walls hold, the shock wave reflects off of them, continuing back in the direction from which it came. If this rebounding shock wave maintains enough Damage Value to reach a character, that character is subject to the appropriate blast effect. If the character is struck a second time by the shock wave (once as it headed out and again as it rebounded), the Damage Value of the blast is equal to the combined Damage Value of the two waves.

Does that mean anytime a grenade explodes, you're better off being far from a wall since it will most likely double the blast on you?
Or is it only used when there is more than 2 wall implied? or is it only used when the 2 surfaces are opposite?

  • \$\begingroup\$ Ah, man, don't tell me they left out the the chunky salsa effect in the 5th edition. \$\endgroup\$ – Ross Ridge Dec 11 '14 at 1:42
  • \$\begingroup\$ no, it's still there, just go take a look at my other question "Chunky Salsa Effect" ;) \$\endgroup\$ – Mouhgouda Dec 11 '14 at 13:04

It applies to any walls when indoors.

Yes, you would want to be both as far away from the grenade and as far away from a wall as possible. However if a grenade landed in one corner of a room and you were against a wall in the far corner that would be safest location if there was not something you could huddle behind.

  • \$\begingroup\$ @Mouhgouda keyword in your rules text is "Confined space" which is why I said "when indoors" in my answer. Nvoight also seems to agree. \$\endgroup\$ – Joshua Aslan Smith Dec 10 '14 at 16:52
  • \$\begingroup\$ ooooooooh, makes a lot more sense. It seems i read like a ferret today as well. \$\endgroup\$ – Mouhgouda Dec 10 '14 at 18:07
  • \$\begingroup\$ how big should the room be to start losing that property? Like, half as big as the explosion? \$\endgroup\$ – Mouhgouda Dec 10 '14 at 18:41
  • \$\begingroup\$ @Mouhgouda I could give you conjecture but nothing with a solid rules basis, sorta a problem with the edition/system as a whole with 5e's release \$\endgroup\$ – Joshua Aslan Smith Dec 10 '14 at 19:10

The keyword here is Confined Space. That means a closed room. If you have a single wall, like you stand outside a house next to it's outer wall, the explosion has room to spread in all directions. With a wall in one direction, it will spread equally in the other three directions. Only when all directions are blocked and there is no room for the explosive energy to dissipate, the victim gets hit a second time, to simulate the added damage in a closed room.

So to make a long story short: don't be anywhere near explosives in general. And don't be anywhere near explosives if you are inside a closed room. That's even more deadly.

  • \$\begingroup\$ That does a boatload more sense \$\endgroup\$ – Mouhgouda Dec 10 '14 at 16:59
  • \$\begingroup\$ well if a grenade landed near a wall the explosion would move in all directions and would still scatter off the wall that is there. The effect would be less than say in a confined space. \$\endgroup\$ – AquaAlex Dec 11 '14 at 8:30
  • \$\begingroup\$ That is why smart 'runners don't take the lift, chummer. Ever. \$\endgroup\$ – Mindwin Aug 31 '16 at 15:22

I don't necessarily think so. While being close to a wall does invite overpressure damage, your alternative is likely being closer to the center of the blast and taking the full damage. Depending on how far away the wall is, I would much rather take the reduced damage, plus a minor amount of overpressure. In general it is better to be as far away from the explosion as possible, wall or not. Strictly speaking it is better most times to be in a corner since this likely will maximize your distance from the explosion and also only subject you to overpressure once. Otherwise anywhere else in a room is likely to subject you to multiple overpressure effects if the rooms is small enough (imagine the blast bouncing off 3 or even all four walls). A friend of mine actually did a model of this in excel with a heat map showing the damage break down. The analysis was that the corner is always best.

What Joshua said about being indoors is a very important point. As to what constitutes a confined space ... well if the blast can reach walls on all sides and rebound due to overpressure, then you are in a confined space, it's just that simple.


An analogy that might help is sound waves. Think about how sound echos in a small room with hard walls. The blast waves move in the same way; they bounce and reverberate until they fade out. The waves are circular, so they'll always be bouncing perpendicularly against the nearest wall (not "glancing off" or being parallel). However, it's not a echo chamber if it's not closed off (or it is, but the effect is severely reduced).


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