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Rectangular Single Wall Duct & Fittings for Commercial or Industrial HVAC Ductwork Systems

Sheet Metal Connectors, Inc. rectangular ductwork and fittings are one part of our complete line of HVAC products. SMC manufacturers coil line ductwork in 4’-5’-6’ lengths. All ductwork comes standard with stiffening beads. Ductwork is fabricated with either Snap Lock or Pittsburgh longitudinal seams. Sealant is available in the seams upon request. HVAC rectangular ductwork is manufactured in three different styles.

Please refer to the following charts for specific materials, gauges, and end treatments of HVAC rectangular duct.

Rectangular Single Wall Duct Catalog & Specs

Rect. Duct and Fittings


Rect. Duct and Fittings

Straight 90 Degree Tap

Rect. Duct and Fittings

Square Throat Elbow

Rect. Duct and Fittings

Square Throat Angle

Rect. Duct and Fittings

Reducing Offset

Rect. Duct and Fittings

Rectangular Duct Wrap

Rect. Duct and Fittings

Radius Offset

TDC Rectangular Ductwork and Fittings

SMACNA recommended TDC duct is a 4-bolt system with a difference. Instead of cutting, assembling and installing a separate flange onto the ductwork, the TDC flange is roll-formed directly onto the rectangular duct. This provides a solid metal connection that reduces leakage which is why the TDC system is the best for minimum leakage application. A TDC assembly instruction manual is available upon request.

Slip and Drive Ductwork and Fittings

Slip and drive ductwork is the traditional system using s-slip and drive connectors.

Raw Ductwork and Fittings

Raw duct is fabricated for proprietary duct connection systems.

Rectangular Duct Fittings

Sheet Metal Connectors, Inc. manufactures rectangular duct fittings in most sizes and configurations. Fittings are manufactured on our state of the art fabrication equipment. All rectangular duct fittings are fabricated with stiffening beads on duct sizes 19” wide and larger which have more than 10 square feet of unbraced panel. Duct Fittings shall be beaded unless duct will have an insulation covering or an acoustical liner. This requirement is applicable to 20 gauge or less in thickness and 3” W.G. or less. Most rectangular duct fittings are fabricated with Pittsburgh seams. Duct fittings are available completely assembled with all accessories (reinforced, vane and rail, etc…) installed. Fittings are also available knocked down to reduce shipping and handling costs.

Turning Vane and Rail

SMC manufactures several types of turning vane and E-Z rail. Turning vane and E-Z rail are recommended for square throat elbows and tees. When using turning vane and E-Z rail performance is greatly enhanced in the HVAC duct system. Test data is available upon request.

Transverse Joint and Intermediate Reinforcement

SMC manufactures many different types of reinforcement. SMC’s most popular types are as follows:
Tie Rod Reinforcement: threaded inserts installed into each end of thin wall (emt) conduit. These are installed internally at both the joint and/or intermediate duct spacing.
R-Angle Reinforcement: roll formed pre-punched angle iron reinforcement. See chart below.


Sheet Metal Connectors, Inc. duct liner shall be of the specified material, thickness, and density of the contractors request. The duct dimensions shall be increased as necessary to compensate for linear thickness. All sizes shall be listed using outside dimensions. Each layer of duct liner shall be attached with a minimum of 90% coverage of adhesive at the liner contact surface area. Pin placement as in chart below.

ASTM C 1071 Type 1 Replaces HH-I-545B Type 1