Limewash on brick fails mainly for three reasons: grime, salts and sealers. Moss, dirt and loose material are washed off. White efflorescence signals moisture moving through the wall and needs understanding first. And if water beads instead of darkening the brick, an old repellent is present that would stop limewash absorbing.
Wet walls are a cause, not a cosmetic issue. Limewash lets moisture escape but will not stop it arriving, so cracked mortar, failed caulk, spilling gutters or soil against the wall should be repaired or flagged first. Old paint adds a second concern: on pre-1978 houses, Washington’s renovation rules require lead-safe practices and a certified firm for scraping or stripping it.