Why is my metal roof leaking?

Thursday, September 2, 2021

Most of the time a leak in a metal roof can be traced to an installation problem. Here's our list of problems that lead to leakage:

Panels improperly installed -  Homeowner installed roofs often put the male (flange) edge exposed on top, which is opposite of the manufacturer's recommendation. See photo of wrong installation and diagram of correct way below. This defect leaves the panels vulnerable to wind blown water intrusion and back up from rain not exiting the roof quickly such as at valleys and gutters. The lap acts as an anti-suction device when installed correctly.

Flashings missing or not down-lapped - Flashings are intended to waterproof transitions from one plane to another. They occur at walls, chimneys, plumbing vent pipes, skylights, electrical service masts, vent hoods and from one roof slope to another.

Pitch too low - Traditional exposed-fastener roof panels such as 5V-crimp and corrugated are rated for use down to a 3/12 pitch — three inches of vertical “rise” for every foot of “run”. Standing seam and PBR (shown below) can be installed as low as 1/4” or 1/2” in 12” pitch because of their taller profile and either concealed fasteners or screws at the top of the panel ridge. Roofs installed below the manufacturer’s listed minimum pitch are prone to leaking during a heavy rainstorm.

Poor quality or incorrectly installed fasteners - The hundreds of screws at the roofing components are all candidates for leaks if not properly set. Screws can be misaligned, overdriven, under driven or missing. We have seen fasteners that have “backed out” of their original position over time and roofs where all of the screw heads have been buried in mastic as a temporary fix. It’s alway a good idea for pay a little extra for a premium quality fastener.

Dissimilar metals - can cause corrosion and leaks over time but we see this mostly in costal areas where the salt air compounds the reaction. You will likely find corrosion at roofing repairs or vent hoods installed with a dissimilar metal than the panel, as in the picture below.

Age - Most metal roof are warranted by the manufacturer for about 25 years, but can possibly last as long as 40 to 50. However, eventually the protective layer over the steel core deteriorates, exposing it directly to the weather, and rust-through spots start to appear.

    Also, metal roofs are just as vulnerable as asphalt shingles for sheathing damage under the roofing due to long term gutter back ups, and panel and flashing damage from acidic leaf build up.   

• • • • • • • • • • • • • • • • • • • • • • • • • • • • • 

Here’s links to a some of our other articles about METAL ROOFS:

What is the difference between galvanized and galvalume metal roofing?

 What is the average lifespan of a metal (galvalume) roof?

Can metal roofing be used on a low slope/pitch roof? 

• What are the pros and cons of a standing seam metal roof?

 What is a cool roof?

What is the stuff you paint an old mobile home metal roof with to extend its life? 

• Why are there leaves in my attic? 

How do you flash skylight, chimney, and pipe vent roof penetrations on a metal roof? 

 Is a metal roof for a mobile home approved for HUD Wind Zone 3? 

• Can I install a new metal roof over an asphalt shingle roof? 

• Which are the male and female flanges of a metal roof panel?

What is the code required minimum pitch/slope for a metal roof? 

• What color metal roof is best? 

• What is a cool roof made of? 

• What is a PBR metal roof?

    Visit our ROOF AND ATTIC page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.

Water Heaters

Water Heater Age

Wells

Septic Tank Systems

Structure and Rooms

Plumbing Pipes

Termites, Wood Rot

& Pests

Sinkholes

Stairs

When It First

Became Code

"Should I Buy A..."

Park Model Homes

Site

Shingle Roofs

Safety

Stucco

Remodeling

Wind Mitigation Form

Roof and Attic

"Does A Home

Inspector...?"

Pool and Spa

"What Is The Difference Between..."

Radon

Brick

Plumbing

Concrete and

Concrete Block

Metal Roofs

Foundations

Modular Homes

Rain Gutters

Mold, Lead & Other Contaminants

Condominiums

Older and

Historic Houses

Crawl Spaces

Mobile/Manufactured Homes

Building Permits

Life Expectancy

Clay Soil

Insurance

Floors

Insulation

Toilets

Exterior Walls & Structures

Generators

Common Problems

HUD-Code for

Mobile Homes

Garages and Carports

Flat (Low Slope) Roofs

Electrical Panels

Sprinkler Systems

Electrical Receptacle Outlets

4-Point Inspections

Hurricane Resistance

Frequently Asked Questions (FAQ)

Home Inspection

Heating and Air Conditioning

Building Codes

Fireplaces and Chimneys

Inspector Licensing

& Standards

Energy Efficiency

Washers and Dryers

Electrical

Kitchens

Doors and Windows

(placeholder)

Cracks

Electrical Wiring

Click Below  

for Links

to Collections

of Blog Posts

by Subject

Plumbing Drains

and Traps

Appliances

Smoke & CO Alarms

Aging in Place

Top 5 results given instantly.

Click on magnifying glass

for all search results.

Bathrooms

Lighting

AFCI, CAFCI,

DFCI, & GFCI

Sinks

Air Conditioner & Furnace Age/Size

Attics

Electrical Switches

Siding

Search

This

Site

Water Intrusion

Electrical - Old

and Obsolete

(placeholder)

Foundation Certifications

Tiny Houses

How To Look At A House

McGarry and Madsen's home inspection blog for buyers of  

site-built, mobile/manfuactured and modular homes

About Us