Multifamily Inspection Services

During a multifamily due-diligence inspection of this 226 unit complex, there was an opened up exterior wall along a parapet cap. This uncovered asphalt-impregnated fiberboard, commonly called “blackboard sheathing.” This material was manufactured with a felt-like black outer surface bonded directly to the board — and it was commonly used as exterior wall sheathing behind stucco on older apartment complexes.

What I found:

✔️ Blackboard sheathing used as the wall substrate
✔️ Factory-applied felt-like asphalt surface
✔️ Stucco installed over it, creating long-term moisture concerns
✔️ Evidence of deterioration, softness, and water intrusion
✔️ Conditions that lead to stucco bulging, cracking, and delamination

Why this matters for investors

Blackboard sheathing is moisture-sensitive, and when it gets wet it:

Softens and loses structural strength

Causes the stucco to separate or “bubble” outward

Provides an easy entry point for termites

Leads to hidden damage that can be extremely costly to repair

Is commonly found on multifamily buildings constructed from the 1950s through the 1990s

This is a major reason older apartment complexes experience stucco failure, wall movement, and envelope breakdown.

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