Isso é coberto pelas regras padrão da Capa . Em parte, isso diz
Cover grants you a +2 bonus on Reflex saves against attacks that originate or burst out from a point on the other side of the cover from you. Note that spread effects can extend around corners and thus negate this cover bonus.
Além disso, embora não seja explícito, o efeito de argamassa se comporta de maneira semelhante a um efeito de rajada, conforme definido nas regras Mágicas .
A burst spell affects whatever it catches in its area, including creatures that you can’t see. It can’t affect creatures with total cover from its point of origin (in other words, its effects don’t extend around corners). The default shape for a burst effect is a sphere, but some burst spells are specifically described as cone-shaped. a burst’s area defines how far from the point of origin the spell’s effect extends.
Como um aparte, apesar do que as regras do morteiro dizem ... Eu também teria afetado objetos.