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Home Repair: How to Flatten Basement Air Ducts to Gain Space

The easiest way to gain valuable headroom

FH11JAU_FLADUC_02-2Family Handyman
Install wider, flatter heating and cooling ducts (you can have them custom made) to increase headroom in your basement, especially when finishing the ceiling.

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Replace a low-hanging duct

Photo 1: Disassemble a duct joint

Unbend the folded portion of each joint’s “drive coupler.” Pull each one off with pliers. Support the duct with two spring clamps and chain and then remove the duct hangers.

Photo 2: Install the new duct

Hoist the new duct into place and hold it with the spring clamps and chain. Line up the joints and insert the top and bottom edges into the S-slips. Install the drive couplers and bend the ends with a hammer. Then install the duct hangers.

Don’t let low-hanging ductwork scuttle your plans for a basement remodel. If the ductwork is in the way, you have three options. You can reroute it or split it into more but smaller ducts. But the least disruptive and easiest way is to replace the low ducts with new ducts that are flatter but wider. In most cases, you can gain several inches of headroom.

Measure the existing ducts that are too low. Sketch out the current duct layout and note the location of each joint. Take the sketch to a professional heating contractor and get a quote for building new, flatter ducts. If the new ducts provide enough headroom, just deliver the old ducts to the contractor to use as a template for the new ones.

To disassemble a duct joint, remove the drive “couplers” (Photo 1). Then install the new duct (Photo 2). Seal all the joints with aluminum duct tape or duct-sealing caulk.

Required Tools for this Project

Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.

  • 4-in-1 screwdriver
  • Drill/driver - cordless
  • Hammer
  • Pliers
  • Safety glasses
  • Spring clamps
  • Stepladder
You’ll also need leather gloves.

Required Materials for this Project

Avoid last-minute shopping trips by having all your materials ready ahead of time. Here’s a list.

  • Drive couplers
  • Duct hangers
  • Duct sealant
  • New thinner ducts
  • S-slips