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Here we explain the causes of moldy attics or roof mold in buildings, and we discuss the relationship between other building moisture sources (such as a wet basement) and attic and roof mold contamination. This document gives advice on how to find and deal with mold in building attics and roof cavities; We discuss when and how to clean up attic mold - how to get rid of attic or roof mold.

This is a chapter of "How to Look for Mold" which describes how to find mold and test for mold in buildings, including how and where to collect mold samples using adhesive tape - an easy, inexpensive, low-tech but very effective mold testing method. The page top photograph of dark mold found on the attic-side of plywood roof decking was contributed by David Grudzinski, a Cranston RI professional home inspector and member of ASHI and NACHI.

© Copyright 2010 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

ATTIC MOLD CAUSES

As this moldy attic photo (courtesy of David Grudzinski) also shows, mold on roof decking or roof framing may be quite extensive. If you look closely at the buckling plywood in the upper right of this photograph, you may notice some cracking that might indicate that the plywood roof decking is actually delaminating and badly damaged. If that proves to be the case, this mold cleanup job will be simplified, but more costly as roof decking may need to be removed and replaced. When we see an attic with extensive visible mold on wood surfaces, we also suspect that the fiberglass insulation may also be mold contaminated, or may become so during any mold cleanup job in the area. See INSULATION MOLD for details.

What Causes Attic Mold?

Cleaning up moldy wood surfaces, removing moldy attic insulation, will be a costly but wasted step if we don't understand and correct what caused these conditions in the first place. Below we describe the combination of two critical factors that make for a wet, moldy attic: inadequate roof ventilation and an indoor source of un-wanted or excessive building moisture. A third source, roof leaks, is more obvious and should also be considered in any building inspection for leaks, moisture, or mold.

Inadequate Roof Ventilation

David pointed out in his emailed comments that the attic of this home was not adequately vented. We don't see good, continuous intake ventilation at the house eaves or soffits (the lower roof edges.) We also did not see good roof exit venting along the ridge of the building.

Our example photos (below) show characteristic rust stains around roofing nails in a poorly-vented attic (below left), and the absence of those stains around roofing nails in a well-ventilated attic (below right). Even our poorly-vented attic (below left) was not as severely wet and moldy as the attic in Grudzinski's photos (above).

Our photo of frost on the under-side of an attic roof deck (left) shows another clue of inadequate under-roof ventilation that may be visible if the building is located in a freezing climate.

Regardless of its source, moisture entering the attic from anywhere is trapped in this space - contributing to mold growth and longer term to building rot or perhaps even inviting insect attack on the structure.

If the moisture levels were low, no mold problem may have occurred. But if we combine poor roof ventilation with high moisture levels, we've asked for trouble with mold and rot.

Insulation improvements as well as attic ventilation improvements are discussed at INSULATION INSPECTION & IMPROVEMENT, and at ROOF VENTILATION SPECIFICATIONS we give specific details on good attic ventilation.

Indoor Moisture Sources Causing Attic Mold

Poor insulation & bathroom, dryer, or kitchen fans not vented outside: Mr. Grudzinski also observed that the moldy attic in this home was fed moisture from a combination of poor insulation, and two bath fans that were venting directly into the attic rather than being directed outside. "Poor insulation" means increased heat flow into the attic in cold weather.

Our photo (left, from a different home) shows a rats nest of bath vent fan ducts that the building owner emptied into a building attic. These vents should have been conducted to outside the building.

"Heat flow" into a cold attic means warm moisture-laden air flow from the occupied spaces in the home below is moving into the chilly or cold attic space. This airflow not only increases the cost of heating the home, but it brings up moisture from below into the attic area where water condenses out of the warm air onto cold attic surfaces.

Wet basements or crawl spaces mean wet moldy attics: At BASEMENT MOLD WATER IMPACT another series of photographs by Mr. Grudzinski demonstrates how a wet (rotting, moldy) sub-basement served as a moisture source that was almost certainly a major contributor to if not the main cause of the moldy attic shown in our page top photographs here.

At ATTIC CONDENSATION CAUSE & CURE and at ICE DAM PREVENTION we describe problems caused by inadequate roof ventilation that include not just attic moisture and mold, but ice damming and even leaks into building ceilings and walls. Also see our photo guide to finding attic moisture and mold at How to Inspect Attics for Condensation & Moisture - to Detect & Correct Attic Condensation, Frost, Ice Dam Leaks & Attic Mold

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Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

FIND MOLD in BUILDINGS, HOW TO
  ATTIC MOLD
    ATTIC MOLD CAUSES
    ATTIC MOLD IS A PROBLEM ?
    ATTIC MOLD - IS IT TOXIC?
    ATTIC MOLD, WHERE TO LOOK
    ATTIC MOLD, WHAT IT LOOKS LIKE
    ATTIC MOLD, HARMLESS COSMETIC?
    ATTIC MOLD ROOF TEAROFF
    ATTIC MOLD ENCAPSULANTS
  BATHROOM MOLD
  BASEMENT MOLD
  BASEMENT MOLD WATER IMPACT
  BLACK MOLD, HARMLESS COSMETIC
  CARPET MOLD CONTAMINATION
  CARPET TEST GUIDE
  CRAWLSPACE MOLD
  DRYWALL MOLD
  DIRT FLOOR MOLD CONTAMINATION
  ESSENTIAL STEPS IN FINDING MOLD
  FLASHLIGHT HELPS FIND MOLD
  WHAT MOLD LOOKS LIKE
  Black Mold  Brown Mold
  Green Mold  Red Mold
  Yellow Mold  White Mold
  Invisible Mold
  Meruliporia Mold Photographs
  Mildew Photographs
  Recognize Cosmetic Mold
  Recognize Harmless Black Mold
  Stuff that is Mistaken for Mold
  HIDDEN MOLD, HOW TO FIND
  Photo Guide to Finding Hidden Mold
  Hidden Mold Behind Paneling
  Hidden Mold Between Framing & Sheathing
  Hidden Mold in Flooring & Subflooring
  Hidden Mold in Wall Cavities
  Spotting Hard-to-See Mold
  Use of a flashlight to find mold
  Wall test cuts to spot hidden mold
  Light colored toxic molds
  Moisture Gradients and Mold
  Other Places to Look for Hidden Mold
  INSULATION MOLD
  SAMPLE POINT CHOICES FOR MOLD TEST
  SAMPLING MISTAKES
  USING LIGHT TO FIND MOLD
FLOODS & MOLD CLEAN/PREVENT
MOLD ACTION GUIDE - WHAT TO DO
MOLD EXPERT, WHEN TO HIRE
MOLD RELATED ILLNESS
PREVENT MOLD, HOW TO
MOLD DETECTION & INSPECTION
MOLD APPEARANCE - WHAT MOLD LOOKS LIKE
MOLD APPEARANCE - STUFF THAT IS NOT MOLD

• Thanks to professional home inspector David Grudzinski, Advantage Home Inspections, ASHI cert # 249089, HUD cert# H-145, for contributing the photographs and portions of the technical content used in this article. Mr. Grudzinski, Cranston RI serving both Rhode Island and Eastern Connecticut can be reached at 401-935-6547 fax- 401-490-0607 or by email to Davidgrudzinski@aol.com. Mr. Grudzinski is a regular contributor to InspectAPedia.com - see DECK FLASHING LEAKS, ROT Case Study, and BASEMENT WATER MOLD IMPACT for examples.
  

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

• Books, Complete List of Environmental Inspection, Diagnosis, Cleanup, Air Quality & Design, Inspection, Repair Books at the InspectAPedia Bookstore
• Environmental Health & Investigation Bibliography - our own technical library on indoor air quality inspection, testing, laboratory procedures, forensic microscopy, etc.
• Mold and Allergen Recognition and Identification - Not All "Black Mold" is Harmful; Some Suspect Stuff is Not Mold
  • How to Find and Test For Mold in Buildings - Looking for Mold - A 'how to' photo and text primer on finding and testing for mold in buildings
  • Recognizing Mold: What mold looks like mold identification photos to help identify mold - choosing what to sample in buildings
  • Recognizing Allergens: What various indoor allergens look like - identification photos to help identify pollen, dust mites, animal dander, toxic or allergenic mold - Common Mold and other Allergens, Irritants, Remedies & Advice
  • Stuff that is not mold but is often mistaken for it - things you may not want to test. Also, not all "black mold" is toxic - here are examples of harmless black mold.
  • Mold Action Guide: an easy step by step outline of what to do about mold
  • How to find mold without hiring anyone, for do-it-yourself'ers
  • Associations: Sick House, Sick Building, SBS - Air Quality, Government, Private Associations and Information Resources
  • Mold Test Kits - How to Collect and Send Your Own Mold Sample to our mold testing lab
  • How to find a mold inspector or test consultant: Directory of IAQ,Sick Building, Mold Allergen Testing, Building Investigation Service Providers
  • Meruliporia: the house eating fungus or "poria"
  • Mold Investigation Tips for Home Inspectors how to find mold, where to look, what is likely to be important. Advice to building inspectors intending to inspect or test for toxic or problematic mold indoors, mold inspection methods, and mold test methods which are valid or invalid
  • Mold Risk Levels in Buildings Based on Visual Inspection - simple visual clues help decide on action
  • Mold in Fiberglass Insulation© 2005 comments about a field study in process, & more about health hazards from fiberglass insulation - DJF
  • Frequently Asked Questions About Mold -- check this FAQ list & IAQ Site Map to see if you can find a quick answer to your mold concern
  • When to hire a professional to inspect for toxic mold or other allergens
• ...

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