Types of Underground Ductwork: What You Need to Know
Underground ductwork plays a vital role in regulating airflow throughout your home, especially in slab or crawl space constructions. However, not all underground duct systems are created equal, and some are far more vulnerable to damage over time.
In this post, we’ll break down the most common types of underground ducts, their pros and cons, and what to do if your system shows signs of wear.
Common Types of Underground Ductwork
1. Transite (Asbestos Cement) Ducts
Made with asbestos and cement, these were common in homes built before the 1980s. While strong, they pose health risks if deteriorated or disturbed. Transite ducts absorb moisture over time, weakening the material and creating potential air quality hazards.
📌 Schedule an above-ground air duct inspection if you suspect you have transite ducts.
2. Galvanized Steel Ducts
These metal ducts are durable but vulnerable to rust when exposed to groundwater. As corrosion worsens, air leaks and system inefficiency can develop.
💡 We recommend trenchless duct lining to restore airflow without excavation.
3. PVC (Plastic) Ducts
PVC ducts resist corrosion and are lightweight, but they’re prone to shifting, sagging, or collapsing under soil pressure. Moisture can still accumulate, especially if connections aren’t properly sealed.
4. Concrete Sonotube Ducts
These are formed using concrete-filled molds, often mistaken for sturdy solutions. However, they’re highly porous, absorb water, and eventually break down—especially in humid or wet environments. Concrete degradation can lead to poor airflow, debris buildup, and mold issues.
5. Cardboard Sonotube Ducts
These are among the most problematic. Made with cardboard reinforced with wire, they were originally used as a quick solution but quickly fail underground. Cardboard absorbs moisture rapidly, promoting mold, air contamination, and total structural collapse over time.
💡 If you have Sonotube ducts, underground duct replacementor lining may be the best solution.
How Do I Know What Kind of Ductwork I Have?
The only way to be sure is with a professional camera inspection. At Trenchless Innovations, we use specialized tools to assess the type, condition, and cleanliness of your duct system—without invasive digging.
Protect Your Home with the Right Solution
Whether your ducts are aging concrete, rusting steel, or crumbling cardboard, we can help. Our trenchless technology repairs and restores underground ductwork with minimal disruption and long-lasting results. All types of underground ductwork are prone to drainage issues and other problems with age. Our repair and assessment services are suitable for any of the above duct types. If you are experiencing issues with your underground ducts or have any questions pertaining to them, feel free to give one of our experts a call at 708-758-5070 today!