How To Look At A House

McGarry and Madsen's home inspection blog for buyers of  

site-built, mobile/manufactured and modular homes

How do home inspectors check a roof?

Friday, October 19, 2018

The two main things we look for are: 1) evidence of roof leaks, and 2) age and condition of the roof material. Age and condition are tied together as one item because there’s always a correlation between the two. In the absence of any other information, we look at the condition to determine the approximate age of the roof. Some roofs age a little faster or slower than average but, like people, there are definite signs of middle-age and then the relentless  progression to senior-citizen status.

   Different planes of a roof age in different ways, and we take that into consideration too. The south-facing side of the roof gets the most sun, and therefore the most ultraviolet damage. Conversely, the north-facing side gets the least sun and is more likely to have moss growth or mildew discoloration. Also, the heavy tree cover in many Gainesville neighborhoods can cause staining that makes a roof look older than it’s actual age.

   We try to walk the roof whenever possible, but if it is too steep to safely walk or it’s wet after a rain, then we view it from a ladder at the edge. The surface provides clues for where to look in the attic underneath for leaks: missing or deteriorated flashings, and damaged or severely deteriorated areas of roofing, are noted and warrant a careful look in the attic for water damage. If the home is a type that does not have an attic, like most mobile homes and 1950’s modern ranch designs, we look at ceiling with an infrared camera for evidence of leaks.

    Each roof material shows different signs of age. For shingle roofs, we check tab adhesion (how easy the front edge of each shingle flap can be pulled up) and granule loss on the surface of the shingle. The granules protect the shingle from UV-deterioration and, as they come loose and roll down into the gutter, the roof begins to age faster, with the edges starting to curl up. The photo above shows an example of shingles curling at the front edges and corners. Also, shingles with loose tabs will perform adequately during a normal rainstorm, but a tropical storm, hurricane, or even a severe thunderstorm, will catch the loose tabs and rip them off the roof, with water damage as a result.

   Metal roofs corrode with age, and the fasteners are the first to show rust damage. We also check for proper fastener spacing and correct lapping of the panels.

   Broken and damaged tiles, along with any improper installation, are noted at tile roofs, which are the most difficult to age by condition.

   Built-up and modified bitumen roofs are used for low-slope applications (under “2 in 12” pitch) and show signs of aging similar to shingles, along with “alligatoring” (a spreading crack pattern loosely similar the back of a gator) of the roofing tar. 

   It’s an old cliché, but a good roof is the #1 protective element of your home. And a bad roof, once it starts to leak, can wreak havoc with the interior: staining, mold, and rot follow quickly. So, naturally we take roof condition seriously, and so should you.

    Also, see our blog post 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? 

• Why is my roof leaking?

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 can I tell if a roof has more than one layer of shingles? 

What are the common problems with attic insulation? 

What is the life expectancy of an asbestos cement shingle roof? 

What's the average lifespan of a roof?

Why is it a mistake to replace a roof and not replace its flashings? 

Why is there no attic access hatch in the house?

What is the building code requirement for an attic access hatch, scuttle, or door? 

Does a roof with multiple layers of shingles last longer?

What can I do to prevent roof leaks?

Are roof trusses better than roof rafters (stick framing)? 

Why is a popped nail in a shingle roof a problem? How do I fix it?

What are the most common problems with wood roof trusses?

What causes a lump or dip in the roof? 

If my roof is not leaking, why does it need to be replaced?

How can I be sure my roofing contractor got a permit?

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?

     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.

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