low-slope roof

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Designing a Low-Slope Roof That Works

Metal roofing or EPDM? Insulation above or below the sheathing? Vented or unvented? An owner weighs all the options.

Posted on Nov 9 2015 by Scott Gibson

If only Kevin Hoene's choices for a new roof boiled down to a choice between an EPDM membrane and metal, his life would probably seem a whole lot simpler.

But Hoene, building a new home in Illinois and on the boundary between Climate Zones 4 and 5, will soon be weighing the pros and cons not only of different roof coverings, but also of what type of insulation to use, whether it should go above or below the roof sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen. , and whether the roof should be vented or unvented. In other words, nothing seems off the table.


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Image Credits:

  1. RoofsPlus

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How to Install Rigid Foam On Top of Roof Sheathing

This type of insulated roof assembly limits thermal bridging through rafters

Posted on Apr 3 2015 by Martin Holladay
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UPDATED on December 15, 2017 with information on the U-factorMeasure of the heat conducted through a given product or material—the number of British thermal units (Btus) of heat that move through a square foot of the material in one hour for every 1 degree Fahrenheit difference in temperature across the material (Btu/ft2°F hr). U-factor is the inverse of R-value. alternative.

A roof over a vented, unconditioned attic does not need to include any insulation. However, most cathedral ceilings and low-slope (flat) roofs are insulated roof assemblies: with this kind of roof, the insulation follows the slope of the roof.

Insulated roof assemblies can be vented or unvented. There are lots of different ways to insulate this type of roof, but one of the best methods calls for the installation of rigid foam insulation above the roof sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen. .


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Image Credits:

  1. Image #1: Green Building Advisor - Alex Cheimets job
  2. Image #2: Fine Homebuilding
  3. Image #3: Sipschool.files.wordpress.com
  4. Image #4: Martin Holladay
  5. Image #5: International Code Council

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Building a Foolproof Low-Slope Roof

A homeowner in the Pacific Northwest wants to detail the roof correctly, but it may already be too late

Posted on Apr 21 2014 by Scott Gibson

Carolyn Wood is building a house 80 miles north of Vancouver, British Columbia, and if nothing else she'd like to get all the details in the roof assembly right. The question is whether the house is too far along to let her reach that goal.

The roof, with a 2-in-12 pitch, is framed with I-joists, strapped with 2x4s, and sheathed with 1/2-in. plywood. Above the roof sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen. , the roofers plan to install NovaSeal roofing underlayment and standing-seam metal roofing.


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Image Credits:

  1. Photo courtesy Carolyn Wood

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How to Insulate a Flat Roof

An architect looks for the best way to insulate a flat roof on a contemporary house — at a price his clients can accept

Posted on Jun 3 2013 by Scott Gibson

Most of the houses that Atlanta architect Scott West designs are contemporary, and they typically come with flat roofs. Construction often consists of 12-in. deep I-joists or open-web 2x4 trusses capped with oriented strand board (OSB) sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen. . Roofs are unvented, and the use of recessed can lights is probably unavoidable.


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Image Credits:

  1. James Morgan

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Spraying Polyurethane Foam Over an Existing Roof

Spray foam isn’t just used for insulation — it can also be used for roofing

Posted on Feb 4 2013 by Mike Litchfield

When Taya and Stephen Shoup's old tar-and-gravel roof began leaking, the couple hoped to find a replacement roofing that would be energy-conserving, leakproof, cost-competitive, and reasonably green. As the house's roof sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen. doubled as a finished ceiling, the old insulation was scant. They broiled in the summer and hemorrhaged money during the heating season.


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Image Credits:

  1. Mike Litchfield, Renovation 4th Edition
  2. Taunton Press

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