Rectangular Ductwork

Rectangular ductwork (square ductwork) is used as main trunk lines in an HVAC system. This ductwork is perfect when ceiling space is a concern, rectangular ductwork maximizes the space above the ceiling. We also offer double wall rectangular ductwork for sound and loss reductions.

Get a Quote Today
United Team Mechanical quality

Our Rectangular Ductwork

Rectangular ductwork is beaded for strength, then roll formed along the length and width to join pieces together, and in many cases lined with insulation. Traditionally, rectangular ductwork has been difficult to obtain a less than 10% leakage rate, but with our machines, knowledge, and installation ability we are able to get a system to less than 3% leakage rate.

Quality Suppliers

United Team Mechanical adheres to the following industry standards when constructing rectangular ductwork:

  • ASTM A653-96 Galvanized G90 Steel
  • SMACNA compliant
Icon usa large | United Team Mechanical
HVAC Fabrication and Manufacturing

Rectangular Ductwork Options

Rectangular ductwork is most commonly built in “L” sections, requiring two sections to complete one full joint of duct. We also offer wrap-around (wrapper) for smaller duct and 4-section rectangular duct for larger sizes. Longitudinal seams are either pittsburgh or snap-lock, transverse seams are slip and drive, raw, flange, or TDC.

Rectangular Duct Size

  • 1 piece – wrapper duct (small duct)
  • 2 piece – L shape duct (typical duct)
  • 4 piece – panels (large duct)

Rectangular Duct Length

  • TDC Joint – 56″
  • Slip and Drive Joint – 59″
  • Custom Lengths

Metal Type

  • Galvanized Steel (G-90)
  • Aluminum (.032 & .040)
  • Paint Lock* (24ga & 22ga)
  • Stainless Steel* (24ga)
  • PVS*

*only select gauges are available with this type of metal.

Transverse End Types

  • Slip and Drive
  • TDC
  • Furnace Flange (.5″ & 1″)
  • Raw
  • Flange (.5″, 1″, & 1.5″)

Serving These Industries


Commercial, Office

Renewable Energy

Research, Technology

Advantages of Rectangular Ductwork

If you are tight on space and/or are totally enclosed above the ceiling, then rectangular ductwork could be your best option. Although spiral and oval ductwork are considered more efficient, square ductwork does offer some advantages, consider the following:


Spiral lacks options for liner, acoustics, strength, and sizing constraints. Rectangular excels in all of these areas, offering many different solutions.

Equipment Tie-In

Most all RTU (roof top units), furnaces, large fans, etc. have square connections and often require square ductwork before you can transition to round.


Lower pressure rectangular duct performs very well in rectangular ductwork.

Height Requirement

Square ductwork maximizes the space above the ceiling, allowing for larger, stronger duct.


Square duct can be lined, wrapped, double-wall (K-27), or skinned. Typical insulation is the Sonix XP Duct Liner, Elastomeric | Armaflex, Rockwool | Mineral Wool.


HETO (high-efficiency take-offs) used on rectangular ductwork are more readily available than round taps. Round taps have to be custom built to each system and are not readily available.

Frequently Asked Questions

How do you make rectangular duct?

If you have the equipment then you would not ask this question. If you don’t have the equipment, call us to do it, trust us on this one.

How do you insulate rectangular ductwork?

As with any trade or skill, it takes time to become proficient at wrapping ductwork. Figure the circumference or stretch out of your duct and add a multiplier (typically 6-8 inches). This accounts for the material wrapping around the corners and the thickness of the insulation that adds to your overall stretch out. Tape the insulation to the duct, staple, and tape the seam.

What gauge is HVAC ductwork?

SMACNA (Sheet Metal and Air Conditioning Contractors National Association) has a matrix with the difference pressure classifications, sizes, and classifications to identify the correct gauge metal for your application.

Is duct cleaning a waste of money?

Duct cleaning can absolutely be a waste of money as most of the insulation in the ductwork will catch and hold a majority of the buildup. Although, in some circumstances cleaning ductwork will help improve airflow, air quality, and efficiency of your system.

How much does ductwork cost?

Flat galvanized steel is nearing $1.50 per pound for some gauges. A standard 12×12 rectangular duct (no insulation) in material cost alone is ~$35. Labor is ~$15. Calculate your markup and you will pay ~$50.

How do you miter ductwork?

Mitering ductwork is very simple. Use this formula (remember it by OWL – offset X width / length). This will give you the amount to cut off your ductwork. As a check figure, you can also lean the ductwork against a straight, 90º wall and measure how much the end comes of the ground and transfer that is your measurement.

Cta icon | United Team Mechanical

Let’s Get Started on Your Next Project

We are Utah’s premier HVAC manufacturer, we take great pride in our work, let us know how we can help you with your next project.

Get Started Today