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Old-timer told me to skip the power washer on a soot job
Guy named Hank at the supply house said just use a shop vac and a stiff brush. Told me power washers just push soot deeper into brick. I ignored him. Used a 2000 psi washer on a 1920s chimney in Portland. Soot turned into this nasty black sludge that seeped through the mortar. Took me an extra 3 hours with chemicals to fix it. Has anyone else dealt with power washer blowback on old flues?
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evangarcia3d ago
That bit about the sludge seeping through the mortar is wild (and a huge bummer) but it makes me wonder if the old mortar itself is the real issue here. Most pre-1930s mixes used lime instead of modern Portland cement, which is way more porous and basically acts like a sponge for that soured soot. The power washer probably just blasted the mess deeper into those old lime joints, making it a nightmare to pull back out.
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ninah103d ago
Actually, I'm not sure I agree with that take. Modern Portland cement can be just as prone to trapping moisture if it's not mixed properly or if the wall gets power washed too aggressively. I've seen plenty of old lime mortar joints that held up fine for decades until someone hit them with a pressure washer, but that's more about the force of the water than the lime itself. The real culprit here might be the soot and creosote buildup building up over years of neglect, not the mortar type. A good soak with a mild detergent and a stiff brush can usually pull that gunk out of lime mortar without making it worse.
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