Every metal panel we sell is ordered to your job: your length, your gauge, your color. That's what makes a metal roof go on fast and clean, and it also means the measurements you bring us are the order. Here's how to get them right the first time.
1. Measure the panel length
Panels run from the eave (the low edge) up to the ridge (the peak). The length you need is measured along the slope — not the flat width of the building.
If you can safely get on the roof, run a tape from the ridge down to the outside edge of the eave. Then decide on your overhang, how far the panel should stick out past the edge so water drops clear of the fascia. An inch or two is typical. Add it to your measurement.
At the ridge, panels usually stop a little short so the ridge cap covers the gap. Tell us how your ridge is being finished and we'll help you set the number.
If you can't get on the roof
You can work it out from the ground with two numbers: the run (the level distance from the center of the ridge to the outside edge of the eave) and the pitch (how many inches the roof rises for every 12 inches across). Multiply the run by the factor for your pitch:
| Pitch | Multiply run by |
|---|---|
| 3/12 | 1.031 |
| 4/12 | 1.054 |
| 5/12 | 1.083 |
| 6/12 | 1.118 |
| 8/12 | 1.202 |
| 12/12 | 1.414 |
For example, a 14-foot run on a 4/12 roof works out to 14 × 1.054 = 14.76 feet, a little under 14' 9". Add your overhang and that's your panel length.
2. Count the panels
The common exposed-fastener panel we order covers 36 inches once it's overlapped with the next one. So for each side of a simple gable roof:
- Measure the length of the eave in feet.
- Divide by 3.
- Round up to the next whole panel.
A 40-foot building needs 40 ÷ 3 = 13.3, so 14 panels per side. Other profiles cover different widths, so if you're ordering something other than the standard 36-inch panel, tell us and we'll do the count.
Hip roofs, valleys and dormers are where counting gets complicated, because panels get cut on an angle and the offcuts don't always reuse. For those, a sketch with measurements is worth more than a panel count. Send it to us and we'll work the list out with you.
3. List the trim
Panels cover the field of the roof. Trim finishes every edge, and edges are where leaks start. Measure the length of each of these on your building:
- Ridge: the peak, for ridge cap
- Eaves: the low edges, for eave trim or drip edge
- Rakes: the sloped edges at each gable end (count both sides of every gable)
- Valleys: where two roof slopes meet in an inside corner
- Walls: anywhere the roof runs into a wall, for sidewall or endwall flashing
Trim comes in lengths, so we'll convert your totals into pieces. We form custom trim while you wait, usually in 10-foot pieces you can take home the same visit.
4. Don't forget the small parts
Screws, foam closures at the eave and ridge, sealant tape and pipe boots are what keep a metal roof tight. We'll size these from your panel count, but it helps to know:
- How far apart your purlins or battens are
- How many pipes, vents or other penetrations come through the roof
- Whether you're going over bare framing or over existing decking
We keep fasteners and accessories in stock at the yard, so these can go home with you the day you pick up.
What to bring or send us
Put this together and we can quote the whole roof in one go:
- Building length and width
- Roof pitch, or the run and rise if you're not sure
- Panel lengths, or the measurements to work them out
- The number of ridges, hips, valleys and gable ends
- Where the roof meets a wall
- Number of roof penetrations
- Gauge and color, if you've decided (we can help if you haven't)
- A sketch or a few photos
Not sure about something? Bring what you have. We'd rather help you check a measurement at the counter than have you wait on a panel that doesn't fit.