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How to Inspect Attics for Condensation & Moisture - to Detect & Correct Attic Condensation, Frost, Ice Dam Leaks & Attic Mold InteriorAPedia © Enter your search terms Submit search form   Search This Website - InspectAPedia.com

• How to inspect a building attic for evidence of ice dam leaks, condensation, frost, or moisture
• How to detect roof venting deficiencies, attic insulation defects, and attic condensation problems

This is chapter 4, "How to Inspect in the Attic or Roof Cavity for Signs of an Under-roof Condensation Problem, part of our discussion of "Attic Condensation". This article describes inspection methods and clues to detect roof venting deficiencies, insulation defects, and attic condensation problems, in buildings. It describes proper roof ventilation placement, amounts, and other details.

These recommendations are based on 30 years of building inspections, on the observation of the locations of moisture, mold, ice dams, condensation stains, and other clues in buildings, and on the correlation of these clues with the roof venting conditions at those properties. I have also measured changes in airflow, temperature, and moisture before and after installing roof venting. More in-depth, un-biased, expert information on these topics and on building defect inspection, diagnosis, & repair can be found at "More Information below. © Copyright 2008 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.

Inspecting in the Attic or Roof Cavity for Signs of an Under-roof Condensation Problem

After examining the eaves or lower roof edges, look up at the ridge for a continuous opening on either side of the ridge board, providing an exit vent path. On some buildings I've found that a ridge vent was installed but the installer just nailed it over the existing roof sheathing, forgetting to cut the necessary opening. "Spot vents" on lower roof slopes, or power vent fans are not as good a substitute for the year-round passive venting provided by a ridge vent.

You often will see many drip spots on the attic flooring or insulation (Left photo below). This is caused by moisture condensing on the roofing nails and dropping to the surface below. This is sure evidence of a condensation problem. The pattern of drip marks may be remarkably just like the pattern of roof shingle nails which protrude through the roof sheathing.

Winter condensation on the nails, even forming frost in freezing weather, rusts the nails and stains the roof sheathing around them. Frost later melts off of these nails and drips onto the floor below. The pattern may occur more on the cooler or north slope of the roof.

If attic stains are from roof leaks, (right photo above) they will usually be much larger and will appear on the sides of rafters, on larger areas of the roof sheathing, and on larger areas of the attic floor.

If you see evidence of extensive roof leaks or condensation leaks, I'd also check the insulation and the attic side of the ceiling drywall for a hidden mold problem.

If you see condensation drip stains in the attic (left photo above), you'll be confirming what you suspected from outside -- inadequate ventilation.

Be careful and don't overlook viewing the roof eaves. There could be rotting fascia boards, decaying rafter ends, and delaminating plywood.

Look in that location for moisture-stained roof sheathing, and look carefully for ice dam leak stains into the eaves, such as the water marks shown in this photograph.

How to Inspect the Attic for Moisture - Stains Around Roofing Nails

Rust or stains around roofing nails that protrude through the attic sheathing (they're supposed to stick through) are a clear indication of high attic moisture.

Our photograph at above left shows roofing nails protruding through plywood roof sheathing visible in an attic where there is no under-roof condensation or moisture problem.

Our photograph at above right shows roofing nails which have rusted and stained the roof plywood in an attic where indoor moisture has risen through the building to condense on the under-side of the roof.

Our photo at left shows the typical staining pattern in an attic where there has been modest condensation at the roofing nails.

If you perform this inspection step in winter in a freezing climate you may find frost on these nails. In other seasons or in non-freezing climates you will see rust on the roofing nails and often stains on the roof sheathing surrounding the nail. On an older home that has been re-roofed, you may see these nail-stains but no nails - the old nails may have been removed during re-roofing, leaving just the rust-marked roof sheathing.

Excessive attic moisture condenses on the cool metal surface of the roofing nails, causing corrosion or rust on the nails and stains on the surrounding wood materials. These same condensation points - the roofing nails - will often map exactly the drip stains found on the attic insulation or attic floor below each nail.

Because moisture may enter the attic more at some locations than others, for example over a bathroom or kitchen, nail staining and drip marks will not be uniformly distributed throughout an attic.

How to Spot Attic Mold Due to High Attic Moisture or Roof Leaks

These photos show mold on attic surfaces due to high moisture in that area. While many inspectors notice dark mold or mold-suspect material on roof framing or roof sheathing, it is at least as important, and often more important to spot the light-colored molds that may also be present - often these are the more hazardous, particularly if building conditions cause air movement downwards out of the attic into the living space or into an attic-located HVAC duct system.

The brown/black attic mold on plywood in the left-hand photo is easy to spot and is often an allergen or problematic attic fungus like Cladosporium sp., Pithomyces chartarum, Ulocladium sp., or Aureobasidium pullulans but the light colored mold on the tongue-and-groove pine roof sheathing in the right photo was found to be Penicillium sp. which is more likely to be airborne and transmitted in the building.

If you find significant levels or large areas of mold in your attic the mold should be cleaned - that is, removed. Do not rely on magic bullets like sprays alone. The spray approach does not remove the problem mold and it may spread it into otherwise uncontaminated materials like insulation.

Don't tear off the roof over a moldy attic: Unless the mold-causing conditions have also rotted framing or delaminated plywood roof sheathing, structural removal/replacement, such as a roof tear-off are unnecessary and inappropriate. But don't forget that if you see attic mold the insulation or ceiling drywall below may also be moldy.

See How to Find, Test For, & Remove Mold in Attics for details about where and how to look for attic mold and what to do about it.

Technical Reviewers

Particular thanks are due to experts and also consumers who read these articles and suggest corrections, changes, and additions to the material. Content suggestions, technical corrections and content critique are invited for any of the content at our website.

• Alan Carson Carson Dunlop Associates, Toronto, Ontario. Mr. Carson is a home inspection professional, educator, researcher, writer, and a principal of Carson Dunlop Associates, a Toronto home inspection and education firm. Mr. Carson is a past president of ASHI, the American Society of Home Inspectors Some great illustrations of the proper under-roof ventilation pathways are offered by Carson Dunlop.Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. (727) 595-4211 mark@BestTampaInspector.com 11/06Daniel Friedman - principal author Daniel Friedman, editing, expanding, adding to comments from John Annunziata, P.E. - NY Metro ASHI informal chapter discussions.
• Technical reviewers are invited to comment or ask questions - contact us

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. If you just "scroll down" you'll miss some important articles. See links at page left.

MOISTURE, MOLD, ICE DAM LEAKS in ATTICS & ROOFS
Attic Condensation
Inspect Building Exterior
Comparing Two Houses
Inspect Basements for Moisture or Mold
Inspect Attics for Moisture or Mold
Inspect the Ridge Vent System from the Attic
Inspect the Soffit Vent System from the Attic
Blocked Soffit Intake Vents
Correcting Roof Ventilation
Ridge and Eaves Venting Both Needed
Continuous Soffit Intake Venting Needed
Proper Roof Vent Location
Roof Vent Area Ratios
Un-Vented Roof Solutions
Air Bypass Leaks, Thermal Tracking

More Information on Effects of Building Moisture & Building Diagnostic Inspections and Repairs

More Reading about Dealing with Attic Mold, Identifying, Removing, and Preventing Mold in Attics

Be sure to review HOW TO FIND MOLD: How to Inspect Homes and Other Buildings for Mold - the Basics of How to Find Problem Mold Indoors in our Mold Action Guide. Here are other articles that will be helpful in evaluating attic mold presence, causes, and cures:

• What Mold and Allergens Look Like: mold identification photos to help identify mold - choosing what to sample in buildings
• How to Clean Moldy Wood Framing & Sheathing How to clean/seal mold from/on exposed lumber or plywood subfloor or roof sheathing indoors - some suggestions based on our field and laboratory research
• Lighting, proper use of: proper aiming of a good flashlight can disclose hard to see but toxic light or white mold colonies on walls.
• Mold spores in the Home - a Photo ID Library for detection and identification of mold allergens.
• How to Find and Test For Mold in Buildings A "how to" photo and text primer on finding and choosing the right spots to test for mold in buildings
• 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.
• Simple Adhesive Tape Sampling of Moldy Surfaces - how to send a mold sample to our lab
• Mold Sampling Methods in the Indoor Environment - In-depth article: detailed critique of popular mold testing methods - Is your mold test kit worth the bother?
• Humidity: What indoor humidity should we maintain in order to avoid a mold problem?
• Mold-Resistant Building Practices, advice from an expert on how to prevent mold after a building flood and how to prevent mold growth in buildings by selection of building materials and by anti-mold construction details.

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The Mold Information Center: What to Do About Mold in Buildings, When and How to Inspect for Mold, Clean Up Mold, or Avoid Mold Problems

Home Inspection Construction Consulting Services & advice for home buyers

Use this simple, economical mold test kit by following our instructions on how to collect and mail mold samples to our lab

Environmental Inspection, Testing, & Diagnosis On-Site IAQ, Gas, Air Testing, Mold Investigation, Sick Building Diagnosis, Lab Services, & Remediation Plan Preparation - indoor air quality testing, problem source determination, supporting lab work, written remediation plan addressing removal of environmental and other hazards and prevention of their recurrence.

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