1. Commercial Roof Systems
We shape our buildings; thereafter they shape us. -Winston Churchill
Civil Engineering and Architecture
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2. 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

3. 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

4. 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

5. 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
Vegetated Roof
Project Lead The Way, Inc.
Copyright 2010

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

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