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

Thursday, September 12, 2019

Yes, you can. It is specifically allowed in the 2017 Residential Edition of the Florida Building Code (FBC) at R908.3, Exception 1, with a similar citation in the International Residential Code (IRC):

    A separator sheet between the shingles and the back of metal roofing is often used, but not required. Asphalt or synthetic felt, or even coated kraft paper, can be used. Some roofers prefer to lay down wood purlin strips to screw the metal panels to, thereby creating an air gap between the two roofs, but this technique is more likely to lead to “oil canning,” slight waves of the flat panels that create irregular surface reflections and shading, especially on hot days. It is only a cosmetic defect, but is sometimes quite pronounced. See our blog post What are roofing purlins and battens?

   Installing the metal directly over the shingles saves you the tear-off and disposal expense for the existing roof. Also, in Florida, it means you do not have to re-nail the roof sheathing to meet current hurricane-resistance code standards.

    See our blog posts What is the difference between galvanized and galvalume metal roofing? and Can metal roofing be used on a low slope/pitch roof? for more on metal roofs.

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

Here’s links to a collection of some of our other blog posts about METAL ROOFS: 

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

    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.

How To Look At A House

McGarry and Madsen's home inspection blog for buyers of  

site-built, mobile/manfuactued and modular homes

(placeholder)

Search

This

Site

Search

This

Site

Attics

Air Conditioner & Furnace Age

AFCI, CAFCI, DFCI, & GFCI

Bathrooms

Aging in Place

Appliances

Click Below  

for Links to Collections

of Blog Posts

by Subject

Cracks

Doors and Windows

Electrical

Energy Efficiency

Fireplaces and Chimneys

Heating and Air Conditioning

Home Inspection

Hurricane Resistance

Electric Receptacle Outlets

Electric Panels

Garages and Carports

Common Problems

Exterior Walls & Structures

Insulation

Insurance

Life Expectancy

Mobile/Manufactured Homes

Older and Historic Houses

Mold, Lead & Other Contaminants

Modular Homes

Metal Roofs

Plumbing

Radon

Pool and Spa

Roof and Attic

Remodeling

Safety

Site

"Should I Buy A..."

Stairs

Termites, Wood Rot & Pests

Structure and Rooms

Wells

Water Heaters

Water Heater Age

Septic Tank Systems

Plumbing Pipes

Sinkholes

When It First Became Code

Park Model Homes

Shingle Roofs

Stucco

Wind Mitigation Form

"Does A Home

Inspector...?"

"What Is The Difference Between..."

Brick

Concrete and Concrete Block

Foundations

4-Point Inspections

Rain Gutters

Condominiums

Crawl Spaces

Building Permits

Clay Soil

Floors

Toilets

Generators