How To Look At A House

McGarry and Madsen's home inspection blog for buyers of  

site-built, mobile/manufactured and modular homes

What can I do to prevent roof leaks?

Thursday, July 12, 2018

You can make a roof more leakproof at three stages in the life of your home. The first opportunity comes when designing and building a new house. Later, roof replacement and then the maintenance in-between replacements offer two more chances to enhance leak resistance. 

     Let’s start with three ways to design-in better water resistance for the roof of a new home:

Simple roof shape - A roof like the one shown below is visually appealing, but the complexity creates roof intersections and roof-to-wall junctures that make it more prone to leakage.

A gable or hip roof over a rectangular footprint will be the most trouble-free, but lacks the curb appeal that many homeowners desire. So we recommend trying to get the desired architectural effect with the minimum of roof complexity.

Minimize roof penetrations - Each thing that pokes through the roof surface, such as a skylight, plumbing vent pipe, or gas appliance flue increases the likelihood of water leaks due to failed flashings, sealants and gaskets. Here’s four ways to minimize roof penetrations:

1) A minimum of one plumbing vent through the roof is required by the building code, and you can reduce or eliminate the number of additional plumbing vent pipes through the roof by using air admittance valves (AAVs) and consolidating vent stacks below the roof where possible. 

2) Exhaust fans can terminate through walls or soffit instead of the roof. 

3) High-efficiency gas appliances can be vented through a sidewall.


4) Choosing electric appliances for HVAC and water heater eliminates the flues required for natural or LP-gas units. 

Install a premium underlayment - The underlayment is a secondary layer of water resistant material attached to the sheathing before the roof is installed. It is commonly a 15-lb. or 30-lb. asphalt felt paper that is laid in downlapped strips. But the new synthetic underlayments, which are manufactured from polypropylene and polyethylene, are sturdier and more tear-resistant. Popular brands include RhinoRoof®, Grace Tri-Flex®, and Titanium UDL30®.
    An even higher level of premium underlayment is a self-adhesive bituminous membrane that is also self-sealing for small punctures. If your roofer installs this material, you will get a discount on the windstorm portion of your homeowner’s insurance in Florida. Grace Ice and Water Shield® is a popular brand. 

    Roof replacement is the next opportunity to improve your roof’s water resistance. If the old roof is 3-tab shingle, you can upgrade to heavier-weight architectural shingle, and there are hail-resistant shingles on the market that offer improved impact resistance. Moving up to a metal or tile roof will provide a longer lasting surface. 

    Be sure that your roofer replaces all the flashings along with the roof material. We have seen several budget roof jobs recently where the more difficult-to-replace flashings around the fireplace and roof-to-wall junctures were left in place and the new roof installed over them. Unfortunately, a new roof that starts its life with 25-year old flashings is likely to have flashing problems long before the roof itself deteriorate.

    Examining your roof and doing minor maintenance regularly is another way to prevent leaks or catch and repair them before that do much damage. You can also hire a professional roofer to do regular checks and maintenance on your roof.

    Also, see our blog posts What's the average lifespan of a roof? and Why is my roof leaking? and How can I tell if the house needs a new roof? 

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

  To learn more about roofs and attics, see these other blog posts:

Why is my roof sheathing sagging between the trusses?

Why is granule loss a problem for an asphalt shingle roof? 

What are the mistakes to avoid when doing attic improvements?

What causes roof shingles to curl up at corners?  

What causes shingles to buckle along a line on the roof?

What causes leaks at a fake roof dormer? 

What causes a sagging roof ridge line?

What causes bubble-like blisters in a built-up and gravel roof?  

Why does it cost so much more to replace a steep roof than a low slope roof? 

What is "ponding" on a flat roof?

Is an attic required to have a light by the building code? 

How can I inspect my roof for hurricane damage?

Why is premature curl of roof shingles a problem?

How many layers of roofing are allowed on a home? 

What are the dark lines running parallel to shingles on my roof?

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

How can I make my roof last longer?  

What are the warning signs of a dangerous attic pull-down ladder?

How can I find out the age of a roof? 

Should I buy a house that needs a new roof?

Should I buy a house with an old roof? 

What are those metal boxes on the roof?

What does "lack of tab adhesion" in an asphalt shingle roof mean?

Why do roof edges start leaking?

Why do my dormer windows leak? 

Do home inspectors go on the roof? Do they get in the attic?

Should I put gutters on the house? 

How much of a roof truss can I cut out to make a storage platform in the attic? 

     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

"What Are The

Signs Of..."

Septic Tank Systems

Structure and Rooms

Plumbing Pipes

Termites, Wood Rot

& Pests



When It First

Became Code

"Should I Buy A..."

Park Model Homes


Shingle Roofs




Wind Mitigation

Roof and Attic

"Does A Home


Pool and Spa

"What Is The Difference Between..."




Concrete and

Concrete Block

Metal Roofs


Modular Homes

Rain Gutters

Mold, Lead & Other Contaminants


Older and

Historic Houses

Crawl Spaces

Mobile-Manufactured Homes

Building Permits

Life Expectancy

Clay Soil





Exterior Walls

& Structures


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



Doors and Windows



Electrical Wiring

Click Below  

for Links

to Collections

of Blog Posts

by Subject

Plumbing Drains

and Traps


Smoke & CO Alarms

Aging in Place

Top 5 results given instantly.

Click on magnifying glass

for all search results.






Air Conditioner & Furnace Age/Size


Electrical Switches





Water Intrusion

Electrical - Old

and Obsolete


Foundation Certifications

Tiny Houses

About McGarry and Madsen



Buying a home in North/Central Florida? Check our price for a  team inspection by two FL-licensed contractors and inspectors. Over 8,500 inspections completed in 20+ years. In a hurry? We will get it done for you.

Moisture Problems

Crawl Spaces