Question 1

How many metal roofing panels do I need?

Accepted Answer

Divide the eave length by the panel coverage width to get panels across, then divide the slope length by the panel length for courses up. A 40 ft gable with 36-inch panels needs 27 panels per side if they run full length.

Question 2

How do I measure the panel length for a metal roof?

Accepted Answer

It is the slope distance from eave to ridge: half the building width times the pitch factor, plus any overhang. A 30 ft wide building at 4/12 has a 15.8 ft run per side. Most suppliers cut to that exact length.

Question 3

What is the minimum pitch for a metal roof?

Accepted Answer

Far lower than shingles. Exposed-fastener corrugated panels typically need 3/12, standing seam goes to 1/2:12, and some structural standing seam is approved at 1/4:12. Always check the specific product approval.

Question 4

How many screws per square of metal roofing?

Accepted Answer

Roughly 80 for exposed-fastener panels at standard spacing — about 1.5 per square foot including the lap and trim screws. Standing seam uses hidden clips instead, which is a large part of why it costs more.

Question 5

Should I put metal roofing over shingles?

Accepted Answer

It is commonly done and permitted in many jurisdictions, usually over furring strips to create a ventilation gap. Check that the framing carries the extra load and confirm your local code — some areas require a tear-off regardless.

Question 6

How long does a metal roof last?

Accepted Answer

Forty to seventy years for painted steel and longer for aluminium and copper. Exposed-fastener systems usually need the neoprene washers replaced around year twenty, which is the real maintenance item on that style.

Question 7

Is a metal roof noisy in rain?

Accepted Answer

Over a solid deck with underlayment, no more than asphalt. The noise people remember comes from panels over open purlins with nothing beneath, as on a barn. Residential installs over sheathing are unremarkable.

Question 8

How much does a metal roof cost?

Accepted Answer

Exposed-fastener steel runs roughly $4–8 per square foot installed, standing seam $9–16, and standing seam is where most of the lifespan advantage sits. Both cost more up front than asphalt and less over forty years.

Metal Roofing Calculator

Inputs

Result

Diagram

Formula

References

Measure what the tool asks for

What it does with those numbers

Why it adds 10% waste

Where the numbers come from

What this will not tell you

Related tools & materials

Calculators

Don't forget

Also useful

Frequently asked questions

Cite this page

Embed on your site