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This article describes how to identify and diagnose carpeting stains at the edge of carpets near walls in buildings focusing on the cause of various interior wall and ceiling stains and explains how to recognize thermal tracking, thermal bridging stains, building air leaks, and building insulation defects. Often these stains are mistaken for toxic indoor mold.

When investigating a building for a mold problem, you can save mold test costs by learning how to recognize Stuff that is Not Mold or is only Harmless Mold but may be mistaken for more serious contamination. Save your mold test money, and increase the accuracy of your mold contamination inspection or test for toxic or allergenic mold in buildings: review these items to learn recognize non-fungal materials or even possibly harmless cosmetic "black mold" often mistaken for "toxic fungal growth." Readers should see HEAT LOSS in BUILDINGS. Also see AIR SEALING STRATEGIES and AIR LEAK DETECTION TOOLS as well as AIR LEAK MINIMIZATION. For photos of snow melt on rooftops that also show points of building heat transfer and loss, see STAIN DIAGNOSIS on Building Exteriors.

© 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.

Building Air Leaks & Thermal Tracking Marks on Floor Carpeting Near Walls

Carpeting Stains along the wall/floor juncture: Alan Carson, a home inspection educator and researcher, has pointed out that we often see dark marks at the edge of floor carpeting where it touches or is close to wall baseboard. These marks are likely to be most severe where the carpet meets exterior walls. These carpet stains at walls occur most often on the lower floors where we get infiltration (air moving in to the building space) from the basement or crawl space below. It is the counterbalance to the exfiltration (air moving out of the building space) issues found at the attic level. As outdoor, basement, or crawl space air leaks into the building around wall-floor intersections, the edge of the carpet acts like a filter and collects dirt from the air leaking in.

These carpet stains are not mold: Some people mistake these "carpet edge stains" for toxic "black mold". If the carpet stains are pretty much continuous along the floor/wall juncture of carpeting and not elsewhere, and particularly if they do not appear elsewhere and are not related to other building water leaks, it is not very likely that these stains are mold.

About these photographs of carpet stains: Thermal tracking or "soot tracking" is visible along the wall baseboard in the phtograph at page top - notice that gray line about an inch wide along the carpet where it meets the wall?

The more ugly dark brown stains at right angles to the wall are not thermal tracking but indicate that this floor was wet, causing rust or bleeding from a cabinet which had been placed in this location. This photo is therefore interesting (if a bit confusing) because it shows two different types of carpet staining.

High indoor humidity: If indoor humidity is excessive (say regularly over 50 or 55% RH) we may be encouraging mold growth in a building or we may be inviting excessive levels of dust mite activity which in turn increases the level of allergens in the building.

Usually soot marks, thermal bridging, or thermal tracking stains appear, if at all, in the building interior locations discussed in the remaining sections of this article.

Photographs of thermal tracking and other stains on carpeting

Carpets in a building are sometimes stained right along the building wall, particularly but not only at the exterior walls. Air leaks at the wall/floor juncture can occur due to building movement or simply sloppy original construction.

Air moving upwards through the building (due to upwards air convection currents) may draw incoming air at the wall/floor gap or cracks, thereby depositing dust and debris at that location. The result is a dark stain at the edges of carpeting along the building walls.

More photographs of thermal tracking and other stains on carpetingcan be seen at PHOTO GUIDE TO STAINS on Indoor Surfaces

We welcome more thermal tracking, soot tracking, air bypass leaks, and similar photos of indoor stains as well as text suggestions to expand this detail and would be glad to credit contributors.

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• Thanks to Alan Carson, Carson Dunlop, Associates, Toronto, for technical critique and content suggestions regarding thermal tracking.

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.

THERMAL TRACKING & THERMAL BRIDGING
  What is Thermal Tracking
  Ceiling Thermal Tracking Marks
  Wall Thermal Tracking Stains
  Floor Carpet Thermal Tracking Stains
  Air Bypass Leaks Marks on Insulation
  Thermal Tracking to Diagnose IAQ
  Stains HVAC Supply Registers
  Pet Stains on Floors
  Pet Stains on Walls
  Human Occupant Stains on Walls
  Stains from Candles, Woodstoves, Fireplaces
  Other Stains on Indoor Walls & Ceilings
  What to Do About Thermal Tracking
SIDING WOOD
STAIN DIAGNOSIS on Building Exteriors
STAIN DIAGNOSIS on Indoor Surfaces
STAINS on Indoor Surfaces: PHOTO GUIDE
STAINS on Indoor Surfaces: PHOTO GUIDE
CARPET TEST GUIDE
also see Investigation of Indoor House Dust Debris

More Information on Building Diagnostic Inspections and Repairs

• Attic Condensation and Ice Dam Leaks - Detection and Correcting Venting and Condensation Problems in Buildings
• INSULATION INSPECTION & IMPROVEMENT: Insulation in Buildings: Identification, R-values, Heat loss, Insulation Types, Insulation Characteristics
• Asbestos pipe insulation in buildings
• Brick "Insulation" in Building Walls
• HEAT LOSS CALCULATIONS, Insulation Properties, Definitions of R, K, U values, Insulation Design
• How to Detect and Correct Attic Condensation & Prevent Ice Dam Leaks in Buildings
• Insulation Materials as Indicators of Building Age
• Indoor Air Quality Investigations: Fiberglass in Indoor Air, HVAC ducts, and Building Insulation
• Insulation Identification Photographs - Fiberglass insulation photos, yellow, pink, green, white fiberglass identification in building attics, walls, ducts, other locations
• Insulation Identification Photographs - Cellulose insulation photos, Mineral wool insulation photos, rock wool insulation photos, cotton insulation photos, balsam wool insulation photos
• Insulation Identification Photographs - Vermiculite insulation photos
• Insulation Properties, Table of R-Values, density, moisture permeability, fire safety, aging effects on various insulation materials
• Mold in Fiberglass in Insulation
• Radiant Heat Floor Mistakes to Avoid case history of improper placement of slab insulation and radiant heat tubing
• Thermal Trackingthermal bridging & air leak stains in buildings or on building insulation
• Un-Vented Roof Solutions - How to Prevent Attic Condensation, Ice Dam Leaks, Roof Mold, & Roof Structural Damage in Buildings with Un-vented Roof Cavities
• Vermiculite Building Insulation & Asbestos
• Ice Dam Leaks in building attics and roof cavities, how to inspect for evidence of leaks, identify causes, and correct bad attic ventilation, improper roof venting, and these causes of attic mold or roof structure damage
• Looking for Mold what mold is often found where in buildings - simple technical presentation
• Mold spores in the Home - a Photo ID Library for detection and identification of mold allergens
• 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.
• Animal Allergens: Dog, Cat, and Other Animal Dander - Cleanup & Prevention Information for Asthmatics and regarding Indoor Air Quality.

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