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What’s the difference between a gable and hip roof for my insurance?
Tuesday, October 9, 2018
A gable roof slopes inward on two sides, and the other two sides have a wall with a triangle shape at the top; whereas, a hip roof slopes in on all four sides. The photo above shows intersecting gable and hip roofs: the hip roof is in the back on the main part of the house, and gable roof at the protruding garage.
And here they are again below, represented in diagrams along with other popular roof styles. Hip roofs are more complicated and labor-intensive to build, but are also more wind-resistant in a storm. Gable roofs are easier and less expensive to build, but the triangle-shaped “gable end” is prone to collapse in a hurricane force wind if not properly braced, with a domino-effect knocking down a row of roof framing members once the gable end collapses.
Because hip roofs have been proven in wind tunnel tests to be significantly more hurricane-resistant than gable roofs, there is a windstorm insurance discount for homeowners in Florida that have a roof shape that is at least 90% hip. The calculation is made by measuring the length of the perimeter (edge at fascia) of the roof that is a hip shape as a proportion of the total perimeter. The big gable end at the garage door in the home above would disqualify it for the hip roof discount.
As you might expect with an insurance industry calculation, there are several complicating factors. A gable roof that covers an open entry area, and a porch roof that is attached to the main structure only at the fascia and is not over an enclosed living space, are both not considered as deductions in the calculation of hip perimeter length. Also, a very low-slope or flat roof that is more than 10% of the total roof area over the living space of the home overrides all the other calculations and eliminates the discount.
While engineers and insurance companies evaluate these two most common roof structures based on strength and cost parameters, architects see the two types of roofs as part of their design vocabulary, and it is currently popular to have the main mass of the house topped with a hip roof, with smaller gables added as a kind of embellishment for entry porches, dormers, and garages.
Also, see our blog post Why didn't I get the hip roof discount on my wind mitigation inspection?
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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 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?
• 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?
• What's the difference between an "architectural" and a regular shingle roof?
• What does a home inspector look for when examining a roof?
• Do stains on the ceiling mean the roof is leaking?
• How can I tell if the house needs a new roof?
• Why does my homeowner's insurance want a roof inspection?
• What are the hazards to avoid when going into an attic?
Visit our ROOF AND ATTIC and INSURANCE pages 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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