Commercial Roof Systems We shape our buildings; thereafter they shape us. -Winston Churchill Civil Engineering and Architecture © 2010 Project Lead The Way, Inc.

Commercial Roof Systems Civil Engineering and Architecture Unit 3 – Lesson 3.1 –Commercial Building Systems Commercial Roof Systems Commercial Roof Shapes Pitched Roof Systems Roofing Materials for Pitched Roofs Low-Slope Roof Systems Roofing Material for Low-Slope Roofs Project Lead The Way, Inc. Copyright 2010

Commercial Roof Shapes Commercial Roof Systems Civil Engineering and Architecture Unit 3 – Lesson 3.1 –Commercial Building Systems Commercial Roof Shapes Roofs for small commercial buildings can be similar to residential pitched roof shapes. Shed Gable Hip Gable with Dormer Low-slope Gambrel Gable & Valley Hip & Valley Low-slope roofs (not completely flat) are common in large commercial construction. Project Lead The Way, Inc. Copyright 2010

Commercial Roof Systems Civil Engineering and Architecture Unit 3 – Lesson 3.1 –Commercial Building Systems Typical Pitched Roof Roof Covering Underlayment Roof Deck Roof covering – The outside layer; sheds water Underlayment – Sometimes called “felt” or “paper” and provides temporary protection during construction and a secondary weatherproofing layer during the life of the structure Roof Deck – The structural substrate that carries the roof loads to the roof framing, typically plywood or OSB (oriented strand board) Roof Framing – The structural support for the roof Roof Framing Project Lead The Way, Inc. Copyright 2010

Roof Coverings for Pitched Roofs Commercial Roof Systems Civil Engineering and Architecture Unit 3 – Lesson 3.1 –Commercial Building Systems Roof Coverings for Pitched Roofs Can be similar to residential construction Courtesy US Fish & Wildlife Standing Metal Seam Clay/Cement Tiles Asphalt Shingles Wood/Cedar Slate Project Lead The Way, Inc. Copyright 2010

Pitched Roof Framing (Low Rise Buildings) Commercial Roof Systems Civil Engineering and Architecture Unit 3 – Lesson 3.1 –Commercial Building Systems Pitched Roof Framing (Low Rise Buildings) Wood trusses or rafters Light gauge steel trusses Structural steel trusses Open web steel joists (lower slopes) This photograph shows a commercial facility with light-gauge steel trusses on CMU load bearing walls. Courtesy Greg Thiel Courtesy Isle of Palms Rec Dept. Open web steel joists on tilt-up concrete walls Light gauge steel trusses on CMU load bearing wall Project Lead The Way, Inc. Copyright 2010

Commercial Roof Systems Civil Engineering and Architecture Unit 3 – Lesson 3.1 –Commercial Building Systems Low-Slope Roofs Sometimes incorrectly called “flat” roofs Provide small slope to provide roof drainage and to prevent ponding Low-slope roofs are not flat. They are slightly sloped to roof drains so that water will not stand or “pond” on the roof. Because water moves more slowly on low-slope roofs, the roofing material must be highly resistant to infiltration. ©iStockphoto.com Project Lead The Way, Inc. Copyright 2010

Typical Low-Slope Roof Commercial Roof Systems Civil Engineering and Architecture Unit 3 – Lesson 3.1 –Commercial Building Systems Typical Low-Slope Roof Insulation Surfacing Reinforcing Weatherproofing Surfacing – Protects the weatherproofing and reinforcement Reinforcement – Adds strength, puncture resistance, and dimensional stability to the roofing, and is often combined with another layer Weatherproofing – One or more layers that keep the water from entering the building Roof decking – A material used to span across beams or joists to create the roof surface. The decking for low-slope roofs is often ribbed metal sheets but can be other material such as plywood. Roof Decking Roof Framing Project Lead The Way, Inc. Copyright 2010

Low-Slope Roof Materials Commercial Roof Systems Civil Engineering and Architecture Unit 3 – Lesson 3.1 –Commercial Building Systems Low-Slope Roof Materials Built-up Roof (BUR) membranes “Tar and Gravel” Alternating layers of asphalt and reinforcing fabric Aggregate surfacing Photograph provided with permission from the National Roofing Contractors Association (NRCA) Project Lead The Way, Inc. Copyright 2010

Low-Slope Roof Materials Commercial Roof Systems Civil Engineering and Architecture Unit 3 – Lesson 3.1 –Commercial Building Systems Low-Slope Roof Materials Single Ply membranes Often referred to by chemical acronyms EPDM = ethylene propylene diene monomer Fully adhered (glued), mechanically attached (screwed), or held down by ballast (e.g., gravel) Single ply membranes include a single layer of roofing material. Photograph provided with permission from the National Roofing Contractors Association (NRCA) Photograph provided with permission from the National Roofing Contractors Association (NRCA) wikimedia Fully adhered EPDM roof system Ballasted EPDM roof system EPDM Project Lead The Way, Inc. Copyright 2010

Low-Slope Roof Materials Commercial Roof Systems Civil Engineering and Architecture Unit 3 – Lesson 3.1 –Commercial Building Systems Low-Slope Roof Materials Spray Polyurethane Foam (SPF) system Two component system Rigid closed cell spray foam insulation Protective coating The protective coating provides weatherproofing as well as protection from UV exposure and mechanical damage. Photograph provided with permission from the National Roofing Contractors Association (NRCA) Project Lead The Way, Inc. Copyright 2010

Low-Slope Roof Framing Commercial Roof Systems Civil Engineering and Architecture Unit 3 – Lesson 3.1 –Commercial Building Systems Low-Slope Roof Framing Wood Joists Light Gauge Steel Joists Open Web Steel Joists Structural Steel Structural Concrete Slab Open web steel joist roof framing with metal decking Couresty constructionphotographs.com Project Lead The Way, Inc. Copyright 2010

Commercial Roof Systems Civil Engineering and Architecture Unit 3 – Lesson 3.1 –Commercial Building Systems Commercial Roof Systems Commercial Roof Shapes Pitched Roof Systems Roofing Materials for Pitched Roofs Low-Slope Roof Systems Roofing Material for Low-Slope Roofs Project Lead The Way, Inc. Copyright 2010

Commercial Roof Systems Civil Engineering and Architecture Unit 3 – Lesson 3.1 –Commercial Building Systems Image Resources National Roofing Contractors Association (NRCA) (www.nrca.net) www.constructionphotographs.com www.wikimedia.com U. S. Fish and Wildlife Service Project Lead The Way, Inc. Copyright 2010