What causes “shadowing” on house walls? I always chalked it up to soot from candles, but I recently had a realtor call me about a house that had shadowing on studs, ceiling truss members, and nails/screws in the drywall. The house was built in 1995 and is a typical ranch-style in West Michigan. There appears to have been a “zero clearance” fireplace that may have been wood or gas. Any ideas?
You have it right, most gray stains that outline framing and fasteners on drywall are caused by soot from combustion. The soot is often from burning candles. The worst candles are the good-smelling ones in a glass jug because the flame lacks Oxygen for combustion. A gas fireplace can also cause soot inside a home.
The soot collects near framing and fasteners on outside walls because these areas are slightly cooler and the air slows as it passes by, depositing soot. You will also find soot on horizontal surfaces and around pictures where air flow changes direction.
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