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Nickel alloy and stainless steels replicate the past for the future
By Carrol McCormick
Nickel Magazine, December 2007 -- Increasingly, nickel alloys and
stainless steels are being used in high-profile roof replacement jobs. In many instances, these materials
help to preserve the original aesthetics while providing additional benefits such as workability, resistance
to corrosion, wind uplift resistance, perforation resistance and low metal run-off levels. Three examples
illustrate these advantages: the Parliamentary Library and Notre Dame Cathedral Basilica, both of which are
in Ottawa, Canada, and Saint Raphael’s Cathedral, in Madison, Wisconsin, U.S.A.
Parliamentary Library
The only structure of the original Canadian parliament buildings to survive a fire in 1916, the
Parliamentary Library is a superb example of the Victorian Gothic style. It opened in 1876 after 17 years of
construction and was first restored after a fire in the dome in 1952.
A second, stone-by-stone restoration was completed in 2006 after four years of work. The original slate
roof had long been replaced by copper. The other original roofing materials were 0.48- and 0.70-millimetre
(mm) galvanized iron, from the 1850s, and 567-gram sheet of lead-coated copper (weighing 6.09 kg per square
metre), which had been installed during fireproofing in 1953.
In the recent restoration, copper was used to cover 3,250 square metres of the roof, with sheet lead
applied to the lantern deck roof.
“We decided on a nickel/copper alloy (N04400),
which we use quite a bit,” says conservation architect Spencer Higgins. Higgins and architects from two
companies: Ogilvie and Hogg and Desnoyers Mercure & Associés, chose 0.46-mm-thick N04400
(Monel®) because of its workability and roll-form capability. The material (which contains 66% nickel) had to
be beaten out to form complex curves. “Monel is quite easy to work with,” notes Higgins.
About 1,390 square metres of dull-matte N04400 were used to replace both the galvanized iron and lead-coated
copper. The greyish alloy is similar in colour to the original materials and forms an effective contrast with
the copper roof. It’s also close to copper in galvanic potential. Although the desired service life for the
roof is 50 years, Higgins says the life span of N04400
is in fact nearer to 400 years.
Sheet metal restoration specialists at Markham, Canada-based Heather & Little Limited installed the N04400
using brake-formed double-locked flat seams, soldered joints, and N04400
attachment clips and nails. Roof structures clad with the N04400
include the lantern walls, upper flying buttresses and pinnacles, buttress cap flashing, main roof ribs and
cornice, and lantern window exterior cladding.
As well, 110 square metres of 1.2-mm S31600 stainless steel were used to fabricate built-in stainless rain
gutters.
Notre Dame Cathedral Basilica
By the time 44 years of construction ended in 1885, the Notre Dame Cathedral Basilica, built in the
neo-Gothic and neo-Classical style, had risen to the status of cathedral, then basilica. The church is the
oldest one in Ottawa still in use, and it is the seat of the city’s Catholic archbishop.
The 55-metre-high steeples were originally clad in tin-plated metal dating from the 1840s. The metal had
been repaired over the years with galvanized iron and given several coats of silver-coloured paint. As part
of a restoration that began in 1999, the original cladding was removed and replaced with 2,800 square metres
of embossed, low-lustre-finish, 0.46-mm-thick S30400,
also known as Ezeform-35. This sheet metal, which was designed specially for roofing, blends with the
Cathedral’s stonework and will never produce rust stains on the stonework. Moreover, its colour is faithful
to the silver appearance of the steeples’ original cladding.
S30400
proved economical for various reasons, says Edward Cuhaci of Edward J. Cuhaci and Associates Architects Inc.
“How it was processed and its thin gauge makes it soft and pliable, and it can be cut with tin snips, which
was important owing to the intricate detailed components of the steeples. It’s also stronger than galvanized
steel, aluminum or copper in the same thickness.”
Other benefits include: chemical resistance to atmospheric pollutants including acid rain; cracking
resistance to thermal stresses; abrasion resistance to snow and ice; low metal release to the aqueous
environment and impact resistance to falling ice. As well, because stainless steels do not require a
protective coating, their use does not involve the release of the volatile organic compounds used in
paints.
Stainless steel has high tensile strength and ductility, which allow the use of light gauges (making it
all the more economical). What’s more, it isn’t affected by the corrosive alkaline action of mortar or
masonry and is compatible with aluminum and other building metals.
Stainless has a thermal expansion comparable with copper and is easily formed and soldered, either in the
shop or in the field.
Adds Cuhaci: “No maintenance is required for stainless steel and its durability is unsurpassed. As a roof
covering, it’s fire-retardant, retains its strength at high temperatures and has a high melting point.”
Saint Raphael's Cathedral
Fireproofing is a key consideration for replacement roofing materials.
In December 2004 Heather & Little Limited completed the construction of a new spire for Saint
Raphael’s Cathedral, located in downtown Madison, Wisconsin, U.S.A. The cornerstone of this church was laid
in 1854. It was ready for use in 1862 and the bell tower and original 35-metre spire were added in 1885. In
March 2004, the cathedral was gutted as a result of arson.
The original roofing on St-Raphael’s Cathedral was wood shingles -- later replaced by painted galvanised
iron. This was the new “original” with which candidate replacement roofing materials were compared; wood
shingles are unacceptable for flame spread and serviceability requirements.
“We will always explore in-kind replacement or rehabilitation of the historic material first. However,
weight restrictions, flame spread rating and roofing technology are three significant drivers for change,”
explains Kelly Thompson, principal architect with Facility Engineering Inc., in Madison, the project designer
of record.
Along with copper, Heather & Little Limited used about 650 square metres of 0.46 mm, S30400
stainless steel with a 2B finish, a durable and aesthetic match to the iron, to re-clad the rebuilt spire’s
belfry area, clock faces, cornice, finial and roofing.
As a testimony to S30400’s
flame spread resistance, Kelly notes, “The spire performed perfectly during the fire. Damage to the
architectural metals was limited to some scorching and water damage.”
Carroll McCormick is a Montreal-based freelance writer.
Photos: Heather and Little Limited
Cameron Forbes, Vice President
Heather & Little Limited
3205 14th Avenue
Markham Ontario
L3R0H1
North America toll free: 1-800-450-0659
Phone: +1-905-475-9763
Fax: +1-905-475-9764
Spencer Higgins
Spencer Higgins, Architect Incorporated
Phone: 416-922-7507
301 - 10 Alcorn Avenue
Toronto, Ontario
CANADA
M4V 1E4
Tel: +1-416-922-7507
Fax: +1-416-922-1681
Edward J. Cuhaci
Edward J. Cuhaci and Associates Architects Inc.
171 Slater Street
Suite 100
Ottawa, Ontario
K1P 5H7
Tel: +1-613-236-7135
Fax: +1-613-236-1944
Facility Engineering Inc.
101 Dempsy Road
Madison, Wisconsin
53714
Tel: +1-608-240-9110
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