GREEN ROOF

INSTALLATION

Ulf Waldmann

Mission Valley Roofing, Inc.

The German Experience1960s West Germany was 60% the size of California with a

population of 60 million

Due to rapid population growth, economic expansion and

industrialized agricultural production open natural space was

dwindling and green roofs were installed to replace these spaces.

Green roofs were not necessarily looked at as usable space.

Extensive sedum

covered green roof

installed in 1962

The German Experience cont.

1974 The large Green Roof on the Karlsruhe Hospital was used in a

scientific study about climatological consequences of vegetated

roofs. Stormwater retention and filtering was the largest benefit.

1979 Established Green Roof Supply Companies were present and

very extensive systems developed.

W & M Roofing

Office Bremen

Germany

Installed 1984

over SBS Torch

applied membrane

The German Experience cont.

1982 The FLL (German Landscaping Research

Association) published their first guidelines for green

roofs which were adopted as industry and test

standards and are still the leading source of info today.

In the 80s local governments started to mandate green

roofs and grant incentives. One incentive were reduced

waste- and storm water fees.

The German Experience cont.

1990 The FBB (German association for all professions

related vegetation on buildings) was founded.

To date an estimated 160 million sq. ft. of roofs are

vegetated, 95% of which is “Extensive”

The most extensive lighweight systems in Germany are

1 ½” thin

Extensive Green RoofExample: Haseco-Zoger Bremen Germany

General Types of RoofsSLOPED and LOW SLOPE ROOFSWe do not call them flat and steep roofs because all roofs should have slope!

Sloped Roof A sloped roof is any roof with a slope of 3” per 12” or more or 14

degrees. Sometimes 2” in 12” is still considered sloped.

Roofing is installed under the assumption that water sheds off the

roof quickly.

Common roofing materials are: Shingles, Tile, Slate, Metal

Low Slope Roof A slope of less than 3” in 12” but no less than ¼” in 12”

Roofing or Waterproofing is installed assuming that water may

“stand” on the roof for a while

Roofing Materials are installed in a manner that results in a

“Membrane” and associated flashings that should be able to

tolerate standing water for a limited time. (48 hours)

Sloped RoofExample of S-Tile, Flat Tile and Solar Tile

Low Slope RoofExample Membrane Roof

Typical Green Roof Layers

Roof Membrane Types

In the roofing industry we speak of roof systems.

The waterproofing component of the system is the

roof membrane. There are three basic types of

membranes currently used for Green Roofs:

1. Bituminous (or Asphalt)

2. Thermoplastic Single Ply

3. Cold applied liquid

Bituminous Membranes Bitumen is the correct name for asphalt, a byproduct of

Oil refinement. It succeeded coal based “TAR” as the most widely used roofing product in the 1950s.

Conventional Asphalt (non-modified) Built-Up Roofs are not suitable for Green Roofs due to insufficient density, flexibility and their support of organic growth.

Single Ply installation of modified bitumen membrane (one layer of APP or SBS) is not recommended.

Need root barrier and/or root growth inhibitors. E.G. copper reinforcement or chemical fillers

SEBS Hot applied rubberized asphalt is the most widely used and proven bitumen based system for green roofs (American Hydrotech, Monsey Bakor)

Not Suitable BUR Gravel

Not Suitable Standard Non Modified

Mineral Surface BUR

San Diego City College

Installed membrane

Possibly suitableModified Bitumen roof if more than one layer and with root inhibitors

Cold Applied Liquid Membranes

Solvent based waterproofing coatings

usually with a reinforcement of fabric.

Most common are polyurethanes.

Well proven in below grade waterproofing

applications.

VOC emissions and environmental

conditions during installation can be

problematic.

Thermoplastic Single Ply

MembranesThermoplastic Single-Ply membranes are usually PVC or TPO

(Thermoplastic Olefin) rolled goods with the ability to be fused together by

heat welding. These membranes have first been used in the 1960s in

Europe and are currently the fastest growing and largest roofing segment

on Earth.

TPO and PVC membranes are root proof, no inhibitors needed. Root barriers may be specified but are not required.

Hot air welded seams will prohibit root penetration.

Can be applied as ballasted systems i.e. loose laid with little fastening.

Are the more economical choice for green roofs.

60 mils minimum thickness recommended or more for “intensive” roofs.

Flashing techniques and details require little to no maintenance and are less prone to root penetration.

They are light weight and safe to install.

Hot Air Welding

General Roof Installation

Safety & Fall Protection Cal OSHA requires fall protection equipment for any

construction work performed over 15 feet.

Federal OSHA guidelines are more stringent but only apply for work on Federal Government property

Fall protection measures can be:

1. Guard Rails

2. Personal Fall Arrest Equipment (Harness, Line and Anchor)

3. Warning Line or Safety Monitor.

All ladders have to be securely tied off at the top and have to extend 36” over the landing.

Fall protection and safety orders should also be followed during maintenance operations.

General Roof Installation

Considerations

Positive drainage is a “must”. Plants don’t tolerate

standing water. Small ponding can be allowed if the

drainage layer is thick enough.

Flashing heights for penetrations and walls should be

increased to allow for thickness of planting substrate and

plants.

Standard galvanized metal flashings for pipe

penetrations are not recommended for bituminous

roofing in green roof application.

Water tests are recommended because repairs to

defects are more costly after green roof layers were

installed.

Pipe Flashing Detail

Membrane Pipe Boot

Installation Recommendations

continued If loose laid membrane is used and the ballast is applied

later fastening of membrane should be sufficient to not allow roof to be damaged by wind uplift. Perimeter fastening is a “must”.

Important! Install gravel or pavers around penetrations that require maintenance. E.G. drains, pipes, walls and roof edges. Gravel separation at up–going walls is also a fire barrier.

Mechanical equipment of the roof requires the same separation. Equipment that needs frequent service such as HVAC should have a walkway provision for each it without harming vegetation.

Gravel at Edging

Typical Roof Details > Drain

Note the gravel around the drain

Manufacturer’s Specifications

The safest way to specify and install a green roof is to follow the manufacturer’s specifications. Most manufacturers have published green roof specs available.

Currently the specifications in the US are very material intensive. E.g. fully adhered insulation and membrane plus root barrier on TPO roofs. Manufacturer’s will allow less costly alternatives while still guaranteeing their system if asked.

Manufacturer’s Labor and Material warranties of up to 20 years are available.

Manufacturers offer their own filter and drainage products but those may not be desirable for supplier of growth media and plants.

Penguin Enclosure Berlin Zoo

Building Codes

Fire and wind uplift standards for green roofs are still in development.

The roof system in itself should comply with local fire resistance requirements.

It is recommended to comply with wind uplift requirements for non-ballasted roof systems, in case the vegetation and growth media will be removed at a later time.

Drainage should be designed and implemented for a non-vegetated system for the same reason.

Since codes are still in development the insulation “R-value” should currently be the same as for a non-vegetated system. R-values for the vegetation are a benefit but can no be relied on for thermal efficiency due to variability caused by moisture content, plant coverage, etc.

Fire Ratings are classified as U.L. classes A through C. The City of San Diego requires Class A on all buildings.

Wind uplift ratings are usually defined by Factory Mutual (FM) San Diego is an area that requires FM I-60 (60 lbs per sq. ft.) wind uplift for FM insured buildings.

Pavers and green roofBrucker Offices Bremen Germany

Filter and Drainage layers Manufacturers specify different systems

Filter layer is usual spunbond polyester or polypropylene fleece and keeps silt from building up on roof membrane.

Drainage layer could be aggregate (blown clay, rock, etc.) or a manufactured good. It allows excess water to run to drains.

There are products that combine drainage and filter layer.

San Diego City

College

Filter Sheet

Installation

Installation of filter and drainage layers

Mori Residence San Diego

San Diego City CollegeDrainage medium installed at drain boxes only

Plants and growth Media

Use a SpecialistGrowth media is the “soil” the plants grow in and needs

to be specifically formulated for use on roofs, especially

in Extensive systems. Here are different installation

options:

Conventional application of drainage layers, growth media in bulk and bags and planting plugs is currently the most widely used in the US.

Hydro seeding extensive green roof system is the most economical but needs a lot of initial irrigation and does not allow for immediate wind uplift resistance.

Pre-grown mats, rolls or grid could be installed by Roofing Contractor and allow for immediate wind uplift resistance.

Intensive Green Roof Systems are planted like a regular garden.

Separation of Trades

Roof Installation and possibly Filter and drainage layers should be performed by a qualified roofing contractor

In many cases the roofing contractor roof loads and install the growth media.

A landscape professional will plant or seed and establish growth. In Germany the “Roof Gardener” was established as a separate specialty trade. Irrigation if needed should also be installed and monitored by them.

Vegetation on Steep Roofs

Steep roofs for vegetated covering are waterproofed in the same manner as low slope roofs. Traditional steep roof materials like shingles are not appropriate.

Provisions need to be taken to keep the growth media form sliding. There are many prefabricated grids, blocks, etc. available.

Irrigation is more complicated because water will move down the slope quickly.

Wind uplift potential is increased

The amount of sunlight may differ greatly on the roof.

Steep Roof

Steep Roof with blocking to keep

vegetation and media from sliding

Maintenance All roofs require periodic (yearly) maintenance.

Visual inspection of roof details, drainage, sealants, etc. should be followed by correction of all unsatisfactory conditions.

Single-ply and liquid applied

roofs do not require

any maintenance at seams.

The replacement of sealants at

tops of penetrations and at walls

can be done without disturbing

the vegetation.

Maintenance of vegetation should be performed by a landscape professional.

It is desirable to have inspections performed by landscaper and roofer together to address any overlapping issues such as plant growth into roof details.

Failure of the Waterproofing

System Today’s roof systems are very reliable. Total failures are

rare if installed and designed correctly. Root penetration can be avoided by specifying the right materials.

Do not install vegetation over a roof system that is in any way compromised or not suitable for vegetation. Most existing roofs are not and replacement costs for a vegetated roof are much higher.

Membranes under green roofs will last longer than exposed membranes.

95% of roof leaks occur at detail areas. Repair involves removing the gravel around the detail or penetrations and then repairing with conventional methods.

Solar Photovoltaic on Green Roof Can be installed on the same roof.

The cooling effects of the green improve solar performance.

Possible less dust accumulation on solar panels.

Photo Courtesy of

OPTIGRÜN,

Germany

Roof GardenBremen Germany