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EcoCline®/ Barrett Systems – General Design Considerations

 

Structural Requirements

Vegetated roofs weigh more than conventional roofs. Dead loads can range from 15psf to over 100 psf when fully saturated. Barrett requires each retrofit project be reviewed by a licensed Structural Engineer in early design phase.

New construction structural requirements are easily computed and incorporated during early design phase. Barrett or a landscape architect can supply information concerning vegetated roof design load weights.

 

Wind Resistance

Wind uplift pressures imposed on a roof are affected by geographic location, surrounding terrain, building height and parapet height. There are numerous resources dealing with wind resistance of roofs including:

  • American National Standards Institute (ANSI)
  • American Society of Civil Engineering (ASCE)
  • Underwriters Laboratories, Inc. (UL) • Single Ply Roofing Institute (SPRI)
  • Factory Mutual Research Corp (FMRC)
  • National Roofing Contractors Association (NCRA)
  • American Society for Testing and Materials (ASTM)
  • Forschungsgesellschaft Landschaftsentwicklung Landschaftsbau e.V. (FLL

These organizations and others have developed information and formulas to classify a building’s wind load design parameters. Most prominent among these for vegetated roofs is the ANSI/SPRI RP-14 standard which has found its way into national building codes.

Ballast weights are easily adjusted to comply with industry standards.

Wind erosion of the soil can be addressed with a number of design features including geotextile erosion control mats and soil tactifiers. EcoCline extensive media has superior wind resistance, usually without the use of any erosion control mats.

Depending on site exposure, newly planted shrubbery and ornamental trees should be anchored to prevent uprooting. Plant resistance to wind damage can also be affected by the variables of root conditions, soil conditions, wind erosion and water erosion.

 

Fire Resistance

Vegetated roofs that are properly designed and maintained are generally considered by the industry to be acceptably fire resistant. EcoCline is rated as a Class A covering per ASTM E-108 and UL-790. ANSI/SPRI VF-1 sets forth general greenroof system requirements and design guidelines for fire resistance which have been adopted by national building codes. Consult local codes for updates and requirements.

Vegetated roofs are typically installed over concrete decks which produce a high degree of interior fire protection..

Intensive vegetated roofs systems are usually irrigated with sprinklers, providing additional fire protection. Local codes may require that both irrigated and non-irrigated systems have firebreaks or fire barriers every one hundred feet, in each direction. Additional vegetation-free zones at all perimeters, roof top openings, drains and wall openings may be used, which add to fire safety features.

Temporary irrigation is recommended during the establishment period. High organic content soil is not recommended for fire-safety and other reasons.

 

Maintenance

It is a standard roofing industry recommendation that all roofs have an ongoing maintenance program. EcoCline-Barrett systems also require a programmed cycle of care and maintenance. The scope of the maintenance program will vary considerably with the planting design, from occasional inspections and light maintenance to daily gardening activity. Maintenance service is readily available from Furbish and a network of approved landscape contractors.

Each project has its own specific details and conditions which will require unique solutions. Barrett and Furbish have a variety of accessory products including water retention fabrics, reservoir mats, drainage mats, root barriers, soil substitutes, aeration and planting mediums, curbing and protection courses that address unique needs with specific components.

Consultation with Barrett representatives and their EcoCline partners can assist you in making the right selections to meet your program.

 

Design Alerts

Flashing heights must rise above the highest possible expected waterline and melting snow drifts, in no event less than 8 inches above the membrane. Flashing conditions and perimeters may be designed without soil cover or plantings in a 24 inch to 48 inch wide path which is typically filled with gravel ballast or precast concrete pavers set on pedestals.

Drains are kept free of plantings and designed with boxes for inspection and maintenance clean-out. When soil depths exceed eight inches, planter drains may be utilized and installed in accordance with manufacturer’s design criteria.

  • If an irrigation system is not installed as part of the system, suitable access to water sources must be provided by the designer.
  • The Landscape Architect may design plantings and select soil mix.
  • Roof loads must be carefully evaluated by a structural Engineer early in the design phase. All calculations must be based upon full saturation conditions, mature vegetation and full live loads appropriate to the project location and code requirements.

 

 Common EcoCline™ Profiles

                             EcoCline 2+1 

EcoCline 3+1 

EcoCline 2+2 

EcoCline 3+2 

EcoCline 2.5+3

EcoCline 3+3

 

 System  Thickness

 3 inches          (2” media    +1”   water  retention)

 4 inches          (3” media    +1”  water  retention)

 4 inches          (2” media  +2”  water  retention)

 5 inches          (3” media  +2”  water  retention)

 5.5 inches      (2.5” media    +3” water  retention)

 6 inches          (3” media    +3” water  retention)

 

 Dry Weight

 13-15 lbs/sf

 19-22 lbs/sf

 14-16 lbs/sf

 22-24 lbs/sf

 20-21 lbs/sf

 23-24 lbs/sf

 

 Max. Fully  Saturated  Weight

 21-22 lbs/sf

28-30 lbs/sf

26-27 lbs/sf

34-36 lbs/sf

35-37 lbs/sf

40-41 lbs/sf

 

 Water Holding  Capacity

 0.9 gallons/sf

1.0 gallons/sf

1.5 gallons/sf

1.6 gallons/sf

2.1 gallons/sf

2.1 gallons/sf

 

 Max Rain Event  Capacity

 1.4 inch storm

1.5 inch storm

2.2 inch storm

2.4 inch  storm

3.3 inch   storm

3.4 inch storm

 

 ANSI/SPRI RP-  14 Class

 #2 ballast

#2 ballast

#2 ballast

#2 ballast

#2 ballast

#2 ballast

 

 MDE Runoff  Curve Number

88

88

77

77

<77

< 77

 

 Maximum  Water  Retention  (ASTM  E-2397  & 2399)

44%

37%

55%

47%

60%

55%

 

 Other EcoCline profiles are available to meet stormwater and weight requirements for your project.

 

 

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http://www.barrettroofs.com

Last Updated: 10.01.2015
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