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How to Reroute a Heating Duct

Elizabeth Knoll

Home remodeling can be fun and exciting. With the excitement, however, often comes extra work. One extra task may be to reroute a heating duct that is in the way. Heating ducts are often installed in basements without future thought on how a homeowner might want to remodel.

  1. Disconnect the duct work trunk that needs to be rerouted. For a round duct, unscrew the pipe and slide it apart. Disconnect a square duct by pulling off the drive cleats. Bend the folded-over parts of the cleats straight, clamp on a vice grips and hammer the cleat off. Repeat for the other side. (See reference 2 for pictures of s-slips and drive cleats.)

  2. Measure and mark a layout for the rerouted duct.

  3. Reconnect your round duct by inserting the crimped end of the pipe into the non-crimped end. It should slide in anywhere between 1 and 1-1/2 inches. Screw together with at least four sheet metal screws per connection. Continue rerouting your round duct, following your layout. If you need shorter joints of round duct, cut it down with your aviation snips. Crimp one end with your pipe crimper so it can be connected to the other pipe.

  4. Secure your round duct to the ceiling joists with 1-inch galvanized hanger strap. Screw one end of the strap into a ceiling joist, loop it around the duct, and screw the other end into a ceiling joist. The hanger will look like the letter "U" and the round duct will sit in the middle.

  5. Assemble your square duct using s-slips and drive cleats. Cut two s-slips for each joint of duct 1/2-inch smaller than the dimension of the duct. S-slips will be put on the "raw" edge of the square duct. Slide the next joint's "raw" edge into the pocket of the s-slip. (See figure 2-96 of reference 1 for an s-slip installation diagram.) Cut two drive cleats for each joint of duct 2 inches longer than the dimension of the duct. Slide the drive cleat over the hemmed edges of the two ducts and hammer on to secure them together. Repeat for the other drive cleat connection. (See figure 2-97 of reference 1 for a diagram on inserting drive cleats.) Fold the drive cleat over the s-slips. (See figure 2-98 on reference 1 for a diagram showing the drive cleat getting folded over.) Continue this method until all square duct is installed.

  6. Secure square duct to the ceiling joists by screwing a piece of 1-inch galvanized hanger strap to a ceiling joist. Then screw the hanger strap to the side of the duct, fold 1 inch over underneath the duct and secure with one more screw. Repeat process for the other side of the duct.


Seal all duct work with a water-based mastic for higher efficiency. This can be applied with a paint brush over all seams and connections.


Wear work gloves when handling sheet metal. It is extremely sharp and can easily cause severe cuts.