Sheet metal, duct and the tools to work it — from somebody who did the job.
New here? Start with the ductwork tools list.
Inside the Toolbox
Everything here comes from doing the work. Pick where you are.
Duct & Sheet Metal
How to cut it, connect it, hang it, and fix it when it fights you.
Tools
What actually goes in the bag, what you can leave at the shop, and how to keep it organized.
Money & Sidework
Pricing a job, writing the invoice, and getting paid for it.
For Homeowners
Thermostats, filters and the parts of your system worth understanding.
From the Toolbox
- Drives Won’t Go On? The Duct Was Cut Out of Square
- Duct Take-Offs Explained: Spin-In vs. High Efficiency vs. Start Collar
- How High Should a Thermostat Be Mounted? 48 Inches vs. 60
- How Far Apart Should Duct Hangers Be? What the Standard Says vs. What We Do
- Duct Elbow Came Apart? How to Spin It Back Together
- How to Invoice for Side Work (So You Actually Get Paid)
Who Writes This
I worked the sheet metal trade for about four years and I have not taken a side job in fifteen. These days I manage projects for a general contractor in Salt Lake, which means I still see this work every week — just from the other side of the table.
Everything here comes from doing it or from watching it get done. Tools I actually carried. Numbers I actually see on real bids. Mistakes I actually made, including the ones that cost me a day.
No team, no content mill. Just what I know, written down.
FAQ
How much to add for a filler piece of duct
When adding a filler piece to shorten the duct to a certain length or filling a piece to keep the duct at a certain length, add an inch for each lap at the s-cleat. Typically this is two inches for lapping over s-cleats. Just keep the thought in your mind to add an inch. If needed, draw a diagram on the floor to help reference the needed length.
How to make a hole in duct
Duct is usually made of 28-30 gauge metal in residential applications and can be from 16-26 gauge in commercial applications. For industrial applications, it can be even thicker. The thicker the metal, the harder it is to make a hole. If the hole is for a cutout, there is no need to be careful as long as the area taken out is discarded. Use the back of a hammer (a masonry hammer or roofing hammer are the best for puncturing duct). If care is to be taken, a screw hole can be put in the duct on a marked line and the cut can go from that point both ways.
Does hanging duct take two people
Hanging duct does not take two people. It is much easier if two people are used: one to stabilize the duct and one to install the drives and attach to the hanging supports.
Best ladder position for overhead work
The ladder should be placed where one person can easily install the drives and the other can stabilize the duct in the air.
What is the lap of a drive
The lap of a drive is one inch.
What should the lip of a duct be over a curb
The duct should lip over the roof curb at least one inch. It also needs to be secured with screws so it does not fall under its own weight.
Does a curb have to sit level
Every effort should be made to ensure that a curb is level in three directions: horizontally two ways and vertically. Additionally, the gap between the roof and the bottom of the curb should be shimmed so the curb does not bow under the weight of the mechanical unit.
Why do duct seams need to be sealed
The seams of duct are sealed to keep air from escaping as it is pushed by the furnace through the duct. The fewer holes in the duct, including at duct connections, the more efficiently the air will flow. This means reduced energy costs for the end user and less maintenance on the system over time.