Homeowners have asked, "What is sonotube?  “Why was that product used to form the air duct work?”

Allergy Proof Your Home

Sonotube is a 5"-22" diameter cardboard tube with a paper-thin aluminum lining the inside. It was originally used as a form for concrete piers. Prior to the mid 1950's, builders used sonotube as a form to build the piers that supported “pier & beam” home’s wooden sub-flooring. Beginning in the mid 50's to reduce the cost of building a new home, builders were asked to build homes with concrete slab floors and counter-flow central air conditioning systems,  This meant either the supply air ducts or the return air ducts were buried under the slab along with the home’s water supply lines and plumbing drain lines.

Challenged to find a readily available material to use for conducting air underneath a home, builders in West Texas decided to utilize that same cardboard sonotube; however instead of pouring concrete inside it, they poured concrete around the outside of the paper cardboard tube and connecting galvanized flex joints. At the time it seemed like a great idea because sonotube was readily available, cheap, and solved the current problem of underground air conduction.

Fast forward 30, 40, 50, and now 60 years and consider the current condition of cardboard sonotube buried underground:  (1) Cardboard subjected to seasonally varying levels of soil moisture, as well as the moisture from heavily watered flower beds next to the home’s foundation. (2) Cardboard sonotube flooded with water from a drain or supply line leak or the overflow from a blocked condensation collection pan to the a/c unit. (3) Sonotube only partially encased in concrete and exposed directly to the earth due to sloppy and hurried concrete pouring. Concrete is not water proof so water vapor is continually passing through the footings and slab foundation of your home and ultimately into your living and breathing space via your duct work.

Today the sonotube is disintegrating, mildewing, and growing fungus and mold which are aggravating sources of allergens. Many times I find the sonotube unraveling and collapsing to the point of blocking air flow. All of these factors create a very unhealthy situation for your family.


Our certified and trained technicians offer an affordable way to eliminate dirt, mold, bacteria and other allergens from contaminating your home’s heat and air system! Duct Armor Air Duct Restoration provides better air quality for a healthier you!

Our non-invasive, trenchless air duct restoration is the perfect solution for a happier, healthier home.

  • Restoring Underground Duct Work
  • Lining Overhead Metal Duct Work
  • Mold Encapsulation & Remediation
  • Smoke Damage Repair
  • Rust Encapsulation
  • Eliminate Air Leaks in your Ducts
  • Reduce Dust & Allergens
  • Eliminating Odors
  • Repair Animal Damage
  • Repair Termite Damage
  • Restores all Types of Ducts
  • Commercial & Industrial Ducts
  • Encapsulate Transite Asbestos Cement Ducts
  • Lining Damaged Cardboard Sonotube
  • Increase HVAC Efficiency
  • Non-Destructive Air Duct Restoration
Reduce Allergens in the Home with Duct Armor

Click on the links to the right to download PDF reports for further information on the laboratory testing performed on the Duct Armor patented product.