108
CONTINUING EDUCATION
LANDSCAPE ARCHITECTURE: GREAT OUTDOOR SPACES BY DESIGN EDUCATIONAL-ADVERTISEMENTDESIGN APPLICATIONS FOR ENHANCING
ROOF GARDENS WITH WOOD
Thermally modified white ash, spruce, and
Scots pine decking, cladding, and porch f loor-
ing offer great versatility and durability as well
as an environmentally sourced product for the
design of rooftop decking. Each fiber of the
wood board is modified, using the thermal
modification process of heat and steam to
achieve rot resistance to the core of the board.
This provides decking with a Class 1 durability
rating. Class 1 Durability is a European rating
system that classifies exterior wood products
based on their resistance to rot and decay. Class
1 is the highest possible rating and it means
that, without any additional maintenance and
with proper installation, the wood will remain
resistant to rot for a minimum of 25 years.
White ash and spruce are classified as Class 1
durability. Class 2 durability ratings indicate
that the wood is resistant to rot for 20 years or
more. The Scots pine is classified as Class 2.
As a comparison with other wood species, ipê
from Brazil and old-growth Burmese teak have
Class 1 ratings, while most other tropical rainfor-
est species attain Class 2 ratings or less. Domestic
old-growth cedar can be classified as Class 2,
although currently harvested cedar is mostly ter-
tiary growth so it meets a Class 3 standard, which
indicates resistance to rot for 10 years or more.
In addition to durability, thermally modi-
fied wood provides a product that has a rich,
natural color that is not the result of a stain.
Left untreated with UV-protectant oil, the
boards will slowly age to a stunning platinum
grey. In addition, each board goes through a
milling process that produces an extremely
smooth finish, thus eliminating roughness
and splinters.
Because of its high durability and low main-
tenance requirements, thermally modified wood
offers great versatility for the design of exterior
surfaces, whether for porches, outdoor decks,or roof patios, as thermally modified wood can
withstand foot traffic and harsh weather condi-
tions and still retain its beautiful character and
smooth finish.SUSTAINABLE WOODS FOR DURABILITY
AND AESTHETICS
Thermally modified white ash, scots pine,
and spruce woods are sustainable alternatives
to tropical woods or composites. The wood
is harvested responsibly in Northern Europe
(ash, pine and spruce) and North America
(ash) from naturally renewable forests, making
it a long-lasting alternative to tropical woods
without sacrificing durability and with superior
dimensional stability. The wood is responsibly
harvested by sourcing from a number of dif-
ferent locations around the world, thus leaving
each forest healthy and thriving. The wood is
also shipped via ocean container, which is more
fuel-efficient than rail transportation and nearly
10 times as efficient as 18-wheeler trucks.
White ash, scots pine, and spruce are chosen
as most suitable species for the thermal modifi-
cation process for the following reasons:- These are sustainable wood species that can be
harvested responsibly without contributing to
deforestation or damaging the environment. - These wood species yield the best results via
the thermal modification process, achieving
a Class 1 durability rating.
The thermal modification process uses only
heat and steam, creating cellular alterations that
occur on both a chemical and cellular level in
the wood. The sugar content and water-absorp-
tion capacity of the wood are altered in the ther-
mal modification process, thus modifying both
cellulose and hemicellulose cells.^1 Cellulose is
made up of smaller units of glucose, and hemi-
cellulose is made up of shorter carbohydrate
structure, monosaccharides.^2 Hemicellulose has
the higher oxygen content so the cells of this
cellular group can be altered by slightly burning
these specific cells within the wood before burn-
ing the other cellular groups. This sequential
burning process causes a reaction that creates
additional heat within the wood. The thermal
modification process uses the steam to control
the burning process. This produces wood boards
that are rot resistant for 25-plus years. This pro-
cess also produces wood with greater structural
integrity of the fibers and dimensional stability.
Aesthetically, it provides a simple, beautiful,
timeless wood product that gets better with age.
Thermally modified wood goes through an
extensive testing process for rot resistance, di-
mensional stability, termite resistance, strength,
formaldehyde content, and f lame spread. This
testing ensures wood boards that are durable and
resistant to rot and moisture. The testing process
takes anywhere from a week to several months
depending on the test. The thermal modification
wood. Aluminum planters offer the durability of
metal with a lighter weight, making them easy
to move and place onto rooftop decks.
Planter cubes that are constructed of
lightweight, recycled aluminum are durable,
low maintenance, and designed to withstand
extreme temperatures. This makes them ideal
for rooftop locations that are subject to extreme
winds, sun, and weather. These aluminum
planter cubes can be painted using an industri-
al-strength powder-coating technology devel-
oped with modern aesthetics in mind. Powder
coating is a dry finishing process that is applied
electrostatically and cured under heat, creating
a more resilient finish than conventional paint.
The process does not emit any volatile organic
compounds (VOCs) into the air and allows the
aluminum planter cubes to be coated with any
RAL paint code color. (RAL is a color-matching
system used in Europe to define paint, coat-
ings, and plastics. RAL is an abbreviation for
the Dutch institute that administers the color
standard.) The aluminum planter cubes typi-
cally contain 20 percent recycled content, are
100 percent recyclable, include drain holes and
irrigation sleeves, and are made in the United
States. They come in a variety of size and color
choices, providing a number of design options
for landscape architects.
Wood planters provide another material
option for introducing plants onto a rooftop
garden or a ground-level exterior space. Ipê
wood planter cubes and ipê wood planter cube
tops offer a selection of modular design options
to incorporate seating, storage, and planters
into a ground-level or rooftop space. With the
long-lasting durability of dense hardwoods,
these wood planters and tops can withstand
harsh environments. The warm wood tones
and varied grain provide a natural comple-
ment to wood decking. The wood planter cubes
may have a polyurethane lining and drainage
holes, making plant care and maintenance easy.
Custom sizes and species are available as well.
Modular planter cubes may be used as planters
or with an ipê top for seating and/or storage,
providing f lexibility of design options. Most
planters have drain holes and irrigation sleeves
that make caring for plants or vegetables con-
venient. As a storage unit, they can be used for
seasonal items like cushions or throw pillows.
Lightweight aluminum trays expand the design
options for rooftop environments. Used as a con-
tainment system for architectural rocks or other
deck elements, the low-clearance aluminum trays
integrate seamlessly with the modular planters
and wood tiles, providing designers with a palette
of materials for designing rooftop environments.
Many aluminum trays are corrosion resistant,
made in the United States, and available in a vari-
ety of standard and custom size options that offer
modular integration with a pedestal deck system.Shown is thermally modified white ash
decking board.Photo courtesy of Thermory USA