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Mold Growth on Walls - Causes & Solutions

Project Report > Water Intrusion through Walls

Inspection #: 201031

Reason for inspection:

  • Residents of the home have been experiencing respiratory issues and migraine headaches which they feel may be related to indoor air quality.

Summary of concerns:

  • Water damage in the powder room has likely left remaining mold growth in the exterior wall cavity.
  • The home is poorly ventilated which has caused tVOC readings to be elevated above the normal level in the upper level and basement.
  • Failed siding near the Office may allow water intrusion.
  • Some potential lead and asbestos hazards were noted.
  • Door to garage is not adequately sealed or self-closing.


Adequate Ventilation Not Present

  • Recommended ventilation of residential homes should be between 0.35 and 0.7 air changes per hour (ACH).
  • Desired Ventilation Rate:  0.5 ACH (Air Changes per Hour)

Water Damage to Wall


  • Utilize existing exhaust fans on digital timers to ensure that no less than 134CFM exhaust ventilation is present at all times.
  • Install a ducted Heat Recovery Ventilation system to achieve the required air exchange rate of no less than 134CFM.
  • Create an air exchange system connected to the upper level air conditioning ducting sufficient to achieve no less than 134CFM.

Main Level:

  • The home owner reports a history of long-term water intrusion from failed flashing along the southern wall in this area, the wall was reportedly opened and vented for an extended period of time to aid in drying
  • Some minor water damage noted on hardwood flooring around the West radiator.
  • RH:32.6% Temp:71.7°F CO2:423ppm CO: 0ppm


  • Affected wall shows no signs of continued water intrusion or mold damage.  If the affected wall had not been rapidly dried additional mold remediation work may be necessary in this area.


  • Deformation noted to wall-paper behind painted surface at southwest corner of the room, may be secondary to the home settling from recent jacking and not water damage.
  • Major siding defect behind deck railing at southeast corner of the home, no increased moisture readings or obvious damage in this area.
  • Paint chipping and peeling along window sills
  • Average tVOC 167ppb
  • RH:33.8% Temp:70.6°F CO2:468ppm CO:  0ppm


  • The noted gap in siding must be repaired immediately to prevent water intrusion.

Powder Room:

  • Obvious water damage noted in wallpaper above the window.
  • No exhaust fan located in this area.
  • Average tVOC @ 202ppb
  • Pedestal sink basin very loose.
  • Obvious cleaning of soot from ceiling, likely secondary to scented candle usage.


  • Large amount of stored contents in this area
  • Door to basement does not seal or have self-closing hinges
  • Average tVOC @ 679ppb
  • RH:33.9% Temp:62.3°F CO2:284ppm CO:  0ppm


  • Install appropriate fire-rated sealed door with self-closing hinges to prevent the intrusion of combustion gases or chemicals from this area.

Boiler Room:

  • Potentially asbestos containing pipe insulation noted in somewhat friable condition.
  • Average tVOC level @ 161ppb
  • RH:40.7% Temp:68.4°F CO2:447ppm CO: 0ppm

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