The Roof as a Platform

The Roof As a Platform
THOMAS W. HUTCHINSON, RRC, FRCI, AIA
Hutchinson Design Group, Ltd.
232 East Main Street, Barrington, IL 60010
Phone: 8477564450
• Email:
hutch@hutchinsondesigngroup.com
Proceedings of the RCI 25th International Convention Hutchinson 139
ABSTRACT
With the current administration’s emphasis on solar and alternative energy sources, the
design of wind rooftop solar energy and wind turbine production systems will grow exponentially.
This growth will have tremendous effects on the roofing industry. This paper will begin
to address the roofsystem
assembly components that a roofsystem
designer will need to consider
so that the energy systems can be appropriately integrated into the roof system for this
new use.
SPEAKER
Mr. Hutchinson is a graduate of the University of Illinois with master’s degrees in both architecture
and civil engineering. As a licensed architect in Wisconsin, Illinois, and Ohio, and a registered
roof consultant, Mr. Hutchinson has received recognition globally for his expertise in
roofsystem
design and building envelope issues. He has made numerous presentations globally
on topics such as: keys to sustainable construction, environmentally sensitive and
energyconscious
roofs, and preventing building envelope failures through sustainable construction.
Mr. Hutchinson believes in the complete integration of all building components into
roofing and building envelope system design. Mr. Hutchinson is currently a principal of
Hutchinson Design Group, Ltd., and is a Fellow and past president of RCI, Inc. He is a member
of the American Institute of Architects (AIA), Construction Specifications Institute
(CSI), the National Roof Contractors Association (NRCA), the American Society of Testing
and Material’s (ASTM) Committee D08
on Roofing, Waterproofing & Bituminous
Materials, and RCI, Inc.
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Proceedings of the RCI 25th International Convention
The Roof as Platform
Photo 1 – Roof designers in the past strived to keep all equipment and foot traffic off of the roof.
This 22yearold
ballasted EPDM roof is in excellent condition, in part because of the lack of roof
top activity.
INTRODUCTION
For decades, “Keep it off the roof”
has been the mantra of knowledgeable
roofsystem
designers. Keeping
the roof free of mechanical equipment,
superfluous items such as IT
cables, satellite dishes, antennas,
conduit, gas pipe, and unnecessary
foot traffic has always been a first
means of extending the roof’s potential
service life. This forethought and
hypothesis in the design phase has
actually proved to be correct as roof
system service life rose (see Photo 1).
There were always roofs that not
only required daily foot traffic, but by
their very design, actually demanded
it. Rooftop surfaces, such as those
designed to play tennis or basketball
upon, encompass rooftop pools, and/
or those which required daily mech anical
inspections were the exception
(see Photo 2).
Another factor in the ‘80s and ‘90s
was an emphasis on proactive maintenance,
for which it was always a
challenge to procure the owner’s buyin.
Recent studies by this author on
longterm
serviceproviding
roofs has
revealed that a significant number of
roof systems appear to actually have
performed well because of the lack of
any rooftop activity, including maintenance
(see Photo 3).
CURRENT CHALLENGES TO
THE ROOFSYSTEM
DESIGNER
In recent years, a great many outside
influences have been affecting
roofsystem
design: the USGBC’s
Photo 2 – The author designed
this rooftop tennis court on the
Lakeshore Athletic Club roof to
serve a function besides just
watertightness.
LEED® program; the EPA’s EnergyStar
® program; energy codes; and
an overall acceptance of the environmental
movement, regulation and
code changes to reflect current trends
and subsequent code adoptions by
Proceedings of the RCI 25th International Convention Hutchinson 141
Photo 3 – The 24yearold
fully adhered
EPDM roof at right is still in excellent condition.
As part of the roofing removal and
replacement design 24 years ago, the
author removed all abandoned rooftop
equipment and placed mechanical equipment
below in an effort to “keep equipment
off the roof.”
Photo 4 (inset) – The inclusion of rooftop
equipment such as solar arrays is becoming
more and more common. The designer of
this roof did a fine job of raising the panels
off the roof and spacing the support to
allow for access. It is unknown if additional
protection in the areas of foot traffic
has been installed.
Photo 5 (below): The installation of wind
turbines on roof areas will become commonplace
in the near future. Designing the roof
system to accommodate them as well as
their maintenance is an important consideration
for sustainable roof systems.
code and city bodies. These outside influencers
create a maze of re quirements for the
designer, placing a great deal of liability on
their shoulders without any liability/respon sibility
for these code influencers. As wrong as
this may be, until revisions are adopted, the
roofsystem
designer is obligated to work
within this framework.
With the advent of code adoption, the
recent federal governmental endorsement of
alternative energy sources has inadvertently
increased pressure on the roof’s ability to perform.
Now the roof system must not only provide
watertight and thermal protection, but
also be a work surface for other building components
and, subsequently, a work platform
to support the ancillary rooftop production of
energy. In less than a decade, the concern of
“keep it off the roof” has evolved to “how can
the roof surface be used most effectively for
other nonroofrelated
activities?” The roof surface
has become too valuable a space to be left
underutilized.
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Proceedings of the RCI 25th International Convention
Roofs are now being asked to be
the base support for other functions
that need to be designed and integrated
into the roof system so as to act
almost independently of the roof.
Examples of such roofsystem
requirements
are:
• Support solar arrays, their
installation, and related
cabling (see Photo 4).
• Be a solar energyproducing
surface.
• Support wind turbine energyproducing
equipment, its
installation, and related
cabling (see Photo 5).
• Provide waterproofing and
support to garden roof systems.
• Provide support for and
access to large mechanical
units and related ductwork
and piping (see Photo 6).
• Provide access to and support
rooftop decks and the activities
they encourage
(see Photo 7).
• Provide base for
mobile antennae (see
Photo 8).
• Provide a base for signage.
ACHIEVING SUCCESSFUL
ROOF SYSTEMS AS
PLATFORMS
As with all successful
construction projects, the
necessary first step is planning
and understanding the
required needs of the ancillary
equipment to be placed
upon the roof. Knowing the construction
process and how the building
and roof will be constructed is a benefit
as well. The designer must think
about constructability and design
within those parameters.
Most roof consultants would be in volved
in these decisions in roofing re moval
and replacement projects,
while the purvey of new construction
Photo 6 – The roof of today: Note the solar array, cellular antennae
and large HVAC equipment. The roof has become too valuable,
as a piece of real estate, to ignore.
tends to belong to the architect, engineer,
and registered licensed professionals.
While the process involved for
each is similar for the purposes of this
paper, decisions and implications for
new construction situations will be
as sumed, as they are greater and
broader in scope.
The success of the “roof as a platform”
is achieved through the sucPhoto
7 – Roofs
performing as
platforms for
ancillary activities
need to be
designed to ac commodate
both
the construction
and the use of
the roofs after
installation.
cessful accomplishment of numerous
tasks across a broad spectrum of
phases. These phases can be categorized
as follows:
• Planning and design,
• Construction documents
(construction drawings and
specifications) and the coordination
with other impinging
Proceedings of the RCI 25th International Convention Hutchinson 143
Photos 8A and 8B – Roofs have become prime candidates for the installation of cellular towers.
As such, roofs need to be designed to accommodate for the installation and maintenance of the
tower and the associated piping, cables, etc.
disciplines,
• Roof construction, and
• Roof protection after installation
and during rooftop
equip ment installation.
PLANNING AND DESIGN
There are numerous technical ar ticles,
manuals, and books that deal
with roofsystem
design and details
that are beyond the scope of this
paper. This paper will deal only with
those roofsystem
parameters that
are directly affected by “roofsasplatforms”
design.
As soon as it is known that the
roof will be asked to perform functions
above and beyond those normally
associated with roofs, the de signer
should immediately start a
matrix of those functions, their de sign,
construction, and maintenance
requirements (see Figure 1). For each
item, the effect on the roof and needed
design considerations can then be
determined. This preplanning will
help organize the designer and the
design and coordination issues he or
she will face.
Design Considerations
1) Roof Deck: The use of the
roof as a platform for other
ser vices will most often in volve
rooftop equipment. The
type of equipment, its need
for securement, dead load,
and potential live load weight
will need to be determined
and coordinated with the
equipmentrelated
design en gineer
or structural engineer.
The roof deck and structure
will need to be designed to
IMPACTING ROOFTOP ANCILLARY SYSTEMS
Rooftop System Component Impacting Roof System Design Impacts Required Action
Roof System
Result
Racksupported
Supports will 1. Willl need to be structurally 1. Review with structural
solar array systems penetrate roofs supported engineer
2. Penetrations will need to be 2. Detail redundant flashing to
appropriately flashed resist potential damage
3. Solar panels need to be above 3. Coordinate desing height
roof for access. Define height with electrical engineer.
in solar array; specification Coordinate in specification
coordination.
4. Solar panels will create snow 3. Review with structural
drifting and reduce melting due engineer possible requireto
solar radiation ment to increase deck
gauge; include in metal
deck specification.
1. Detail coordination
2. Detail coordination
3. Equipment and
installation
coordination
4. Life safety
Figure 1
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Proceedings of the RCI 25th International Convention
accommodate the system’s
weights and potential support.
Characteristics such as
potential resultant snow
loads, drifting, and reduced
snowmelt due to shading will
need to be accommodated.
2) Wind: Rooftop equipment
that extends above the roof
surface often results in saillike
manifestations that will
need to be accommodated by
both the structural engineer
and the roofsystem
designer.
Potential wind uplift to the
roof surface by vortexes created
by the rooftop equipment
also need to be considered.
3) Service Supports: The roof top
equipment will require
supports. Optimally, it is recommended
that the equipment
be elevated above the
roof surface on a raised platform
curb so as to isolate it
from the water plane of the
roof. The platform should be
designed to be structurally
sound and fulfill the requirements
of the roof deck and
wind concerns noted above. If
a platform curb is not possible,
an appropriate support
base is required. It should
integrate into the structure
and be able to be appropriately
flashed into the roof
system. It should also provide
proper clearance to the roof
membrane for the purpose of
maintenance or repairs. This
author believes in redundancies,
a theme that will be
repeated numerous times. As
such, the base of the support
should be waterproofed at the
roof deck level, perhaps into a
vapor retarder. Vibration and
harmonic movement will
work on the rooftop flashing
and a secondary barrier will
provide added protection.
4) Vapor Barrier/Air Barrier/
Temporary Roof: The use of
a vapor retarder or temporary
roof as a design element (as
opposed to being required by
building environments) is
highly recommended when
the roof surface will be a platform.
Much of the construction
of the ancillary rooftop
equipment has roofsurface
damage potential from installation
crews unfamiliar with
roof covers and packaging
that can easily damage roof
membranes and flashings. As
such, if a vapor retarder or
temporary roof can be installed
and a large portion of
the rooftop equipment in stalled
working over the
vapor retarder or temporary
roof with the finished roof in stalled
afterward, the inherent
quality of the roof can be
improved. The vapor retarder
or temporary roof also provides
temporary interior protection
from moisture intrusion
and for the installation
of interior HVAC and piping
in dry conditions.
5) Insulation and Protection
of Same: The importance of
thermal insulation has never
been greater. Higher thermal
values and greater insulation
thicknesses are becoming the
norm. The thermal insulation
in roofs of the future will represent
a substantial initial
investment as well as an in vestment
for potential future
savings. As a valued component
of the roof system,
depended upon for energy
savings and roofcover
substrate,
it is now being called
upon to support a roof acting
as a service corridor. As such,
it should be protected from
potential damage. Consequently,
the insulation
should be protected by a
coverboard of substantial
density and pointload
resistance.
Most roofsystem
manufacturers
produce walkways
that protect the roof membrane
but do not have the
thickness to prevent damage
to the roof insulation.
6) Foot Traffic: The roof system
that is requested to perform
as a platform will need to be
designed for heavy foot traffic
and for access to both roof
and rooftop equipment (see
Photos 4 and 10). The key for
roofsystem
designers is to
un derstand construction se quencing.
More often than
not, the roof surface, if need
be, is designed to prevent and
resist physical abuse after
the roof is installed. With
“platform roofs,” the need is
immediate to prevent damage
by those other trades in stalling
energy equipment
such as solar arrays, wind
turbines, hotwater
tanks,
and the like. The roof surface
will be impacted not only by
foot traffic but by material
packaging, tools, sharp materials
as well as workman setup
and construction. As recommended
above, the most
qualityoriented
design parameter
would be to install a
vapor retarder or temporary
roof and allow this work to
take place, and then to have
the new roof installed free
and clear of this other work.
If this is not possible, the use
Photo 9 – A sacrificial protective
layer of 90mil
EPDM
membrane was installed in
and around all the mechanical
equipment on this roof
area as added protection in
addition to the 2in
rubber
walkways.
Proceedings of the RCI 25th International Convention Hutchinson 145
Photo 10 – This solar panel installation allows little room for maintenance
of the roof surface below – a requirement of the roof warranty.
of the most ro bust
and punc tureresistant
membrane is
recommended:
80 and 90 mil
for single plies.
Additionally, in
known areas of
c ons t ruc t i on
and anticipated
ma i n t e n a n c e
foot traffic, a
second sacrificial
protective
layer of membrane
should be
installed (see
Photo 9).
The designer
needs to indicate
in the specifications
who
will provide the
protection. On a
recent project,
this au thor provided
for a roofprotection
allowance so that a roofing
contractor could come in and
protect the roof during major
masonry demolition rather
than asking the masonry
contractor to do so. This scenario
worked well. On new
construction it is recommended
that the installing
roof contractor be required to
provide this protection and
that the specified scope of
protection be defined in the
specification and on the
drawings.
7) Material and Equipment
Stor age: Roofs that will perform
as platforms are doing
so for a reason and typically
will involve the placement of
packaging, equipment, and
assembly construction (see
Photo 11). These activities can
often physically damage not
only the roof membrane but
roof insulation and flashings.
If ropes for fall protection are
required, they should not be
allowed in any way to wrap
roof curbs, vents, etc. Base
flashing corners should be
doubled if it is anticipated
that ropes and extension
cords will abrade them.
The designer should specify
exact protection measures for
material storage, debris storage,
work areas, and assembly.
This author has found
that generic requirements
Photo 11 – Roofs acting as
platforms should be designed
not only to withstand the
impact of constructoin crews
unfamiliar with roofs, but
also the equipment packaging,
debris, and assembly
areas.
such as “roofing contractor
shall protect new roof installation
until accepted by the
owner” are insufficient and
too broad. Is the roofing contractor
to protect the newly
installed roof from every
other trade on the roof? This
never happens and is never
enforced. Specific protection
measures should be specified;
ones on which a contractor
can actually place a definite
number.
8) Specify Rooftop Maintenance:
Following the completion
of the roof and installation
of the rooftop equipment,
the equipment will undoubtedly
require maintenance.
This maintenance, as well as
the first couple years of climatic
cycling, can affect the
roof systems: seams may pop,
flashings pull, punctures and
cuts may reveal themselves,
and debris may accumulate
at roof drainage systems. On
a roof with so much activity
occurring after the initial
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Proceedings of the RCI 25th International Convention
construction, proactive and
specified roof maintenance is
recommended for the first
two years. This can be specified
and included in the project
documents. On large projects,
it is not uncommon to
have the roof completed and
the actual building completion
months and even years
later. By requiring the roofing
contractor to return, minor
items can be attended to
before they manifest into
larger concerns that are not
covered under any warranty.
Designers and owners should
consider this a quality insurance
item.
9) Codes: Roofsystem
assemblies
are tested without
rooftop equipment.
Consequently, the addition of
such equipment on the roof
surface may impact code
compliance. The design professional
must:
a. Verify and coordinate with
the electrical engineer that
all required rooftop electrical
components are codecompliant.
b. Verify compliance with all
ap plicable codes.
c. Consult with the roof
membrane manufacturer
to verify that potential
rooftop products will not
adversely impact the fire
classification of the roof
system.
d. Verify the rooftop equipment
will not produce
wind vortexes that will
result in roofsystem
wind
damage.
CONSTRUCTION CONCERNS
Even the most attentive roofsystem
designer – one who endeavors to
provide a fine set of allencompassing
details – cannot anticipate all construction
sequencing and field modifications
and nuances. As a result, the
roof system acting as a platform for
other concerns will benefit greatly by
onsite observation by qualified roof
consultants and architects who have
been involved in the project. These
individuals need to be able to not only
confirm installation in accordance
with the contract documents, but also
be able to make field decisions and
provide design and details for alterations
as they arise. Field sketches for
conditions that have changed need to
be expeditiously produced and provided
to the appropriate parties.
This individual will also need to
take a leadership role in preconstruction
and coordination meetings, raising
questions regarding sequencing,
protection, and all other concerns
that have potential to damage or
affect the roof system. Leaving this
quality quotient to the general contractor,
builder, or roofing contractor
is often a lost cause.
The receipt, review, and coordination
of shop drawings related to the
specific rooftop equipment is an
imperative exercise. It is an additional
coordination activity prior to construction
– a chance to improve the
roof’s quality. A key activity is the
sharing of information; for example,
solar array racksupportsystem
shop
drawings should be provided to the
architect, who in turn should forward
them to the roofing contractor to verify
detailing. Conversely, any questions
and concerns raised by the roofing
contractor should be shared with
the solararray
installing contractor,
and the process of revising and resubmitting
shop drawings and review
sharing should be commenced again.
COMMISSIONING
The closeout
of projects has often
been said to take 90% of the time with
only 5% of the fee left. Closing out
even a simple project is an arduous
task. The main part of the project is
complete, new projects are on the
horizon, and producing paperwork is
not as much fun as the construction.
Nonetheless, the formal closeout
of a
project and the related paperwork is
an important component of a successful
project. Warranty and closeout
documents, in addition to providing
promises of corrective action, also
provide protection for the owner, contractor,
architect, and manufacturer
as they define an installation and
scope of warranty coverage required
by the contract documents.
Warranty inspection by the roofsystem
manufacturer needs to be
considered and coordinated. If equipment
will cover (hide) pertinent
details, inspections prior to the materials’
installation may be required.
The roofsystem
designer, when
performing “punchlist” inspections,
should look at the entire roof platform
as a holistic concern and indicate all
items that affect the roof system’s
performance. Items that need to be
completed by electricians, plumbers,
and mechanical trades, when coordinated
with the roof “punch list,” tend
to indicate the importance of one to
the other. Obviously, verification of
completion is required.
The owner should be brought into
the commission loop by being
informed of the need for proactive and
continuous rooftop maintenance, as
is required by the roof warranty, common
sense, and by the fact that the
roof has been designed to perform
many functions. The completed roof
system now needs to be managed. All
roof activities should be recorded.
Why? What work has been performed?
Who performed it? Was any
damage done to the roof by the work
performed?
Yes, the roof should be inspected
as a quality assurance measure
before and after any rooftop activity or
ancillary work. The author has found
that when work crews requiring
rooftop access are informed that the
roof was inspected prior to their
arrival and that it will be inspected
after their departure, they realize the
importance placed upon the roof and
are likely to take greater care. Locking
the roofaccess
point and monitoring
access as opposed to unrestricted
access works wonders.
Proceedings of the RCI 25th International Convention Hutchinson 147
RECOMMENDATIONS
To achieve sustainable (30year)
roof systems that serve as a platform
for some type of alternative and ancillary
function in a watertight manner,
the following is recommended.
1. Design the roof and all functions
in a holistic manner,
integrating all items into each
other.
2. Plan and organize the
requirements of each element
impinging on the roof system.
Define each and its potential
effect on the roof system.
3. Design considerations should
take into account:
a. A roof deck of appropriate
strength.
b. A roof deck and structure
that will resist not only
the imposed loads by the
roof system, but also
those created by all
rooftop equipment.
c. Service Supports: Gain a
complete understanding
of how the rooftop equipment
needs to be supported
and how it should be
integrated into the roof
system. Remember that
most of the equipment
being placed upon the
roof has not been
designed with the roof in
mind.
d. Consider the use of a
vapor retarder and/or
temporary roof so that
rooftop construction can
be completed and damage
to the new final roof membrane
is not incurred.
e. Protect the thermal insulation
from the deleterious
effects of repeated foot
traffic, material, and
equip ment storage.
f. Design the roof surface to
be protected from foot
traffic, material storage
(i.e. pallets), debris, and
construction material
assembly. Consider the
use of 2inthick
rubber
walkway pads, concrete
pavers, and additional
layers of membrane.
g. Design and specify specific
rooftop protective measures.
h. Design and specify
rooftop maintenance for
the first two years after
installation.
4. Be involved onsite in the construction
observation, and
provide solutions to field conditions
as they arrive. Look to
see that other trades are
informed of their impact on
the roof.
5. Commission the roof as a
holistic concern at the completion
of construction.
CONCLUSIONS
Roof systems today are required to
perform many more functions than
their predecessors, and by default,
need to be designed in a way that
reflects these new needs. Failure of
building owners, builders, architects,
roof consultants, manufacturers, and
contractors to understand that the
fundamental purpose of the roof is
now being subverted for a greater
good will result in longterm
concerns
and litigious activity.
Taking a holistic approach to the
roofsystem
design, its construction,
and its management will result in
watertight performance while supporting
many other rooftop activities.
The days of the “outofsight
and outofmind”
approach to roof systems is
over. The roof as a valuable contributor
to a building’s environmental, aesthetic,
and energy performance has
now become the norm.
FOOTNOTE
1. Thomas W. Hutchinson, “De signing
Replacement Roof
Systems to Achieve LongTerm
Service Life: A Sustainable
Solution,” 11th
International Conference on
Durability of Building Ma ter ials
and Components (DBMC),
Istanbul, 2008.
REFERENCES
Natasha Biasell, “Innovative Roof ing
Inspires Solar Energy Col laboration,”
Interface, July
2009: 2224.
Philip D. Dregger, “Retrofit Roof top
Solar Voltaics – How to
Save Money on Energy … and
Avoid Spending It on Repairs,”
October 7, 2008 PowerPoint™
presentation.
Michael Gumm, “Integrating Pho to
voltaics onto Building En ve lope
Surfaces,” Interface, De cem
ber 2008: 1123.
Thomas W. Hutchinson, “Design ing
Replacement Roof Systems
to Achieve Long Term Service
Life: A Sustainable Solution,”
11th International Conference
on Durability of Building
Materials and Components
(DBMC). Istanbul, 2008.
Ashley St. John, “Thomas Co. In stalls
a Roof System on the At lantic
City Convention Center,”
Professional Roofing, August
2009.
Ed Kane, division manager of
tech nology for Firestone Build ing
Products, interviewed by
Thomas W. Hutchinson, Octo ber
2009.
Joe Malepezzi, code enforcement
for Carlisle Syntec, interviewed
by Thomas W. Hutchinson,
Oc tober 2009.
Allen Sopko, warranty service for
Firestone Building Products,
interviewed by Thomas W.
Hutchinson, October 2009.
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