砖体要「饱满、规整」才能被灰浆紧密粘合，这正是亲水保湿剂的作用。

它们与灰浆的关系是配合而非替代：保湿剂让砖体含水充足，结构性脂质把砖与砖之间的缝隙封住。

因此 SBT 强调「砖墙同补」——只涂保湿水不补脂质，墙仍然会漏；只补脂质不补水合，砖体也不规整。

Humectants and structural lipids cooperate rather than replace each other: humectants fill the bricks with water, lipids seal the gaps between bricks.

Hence 'bricks and mortar together': water alone leaves the wall leaking; lipids alone leave the bricks dry and irregular.