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Track record
spurs tilt-up growth in Atlantic Canada
By Andy Bateman,
Engineering Editor
From its early beginnings
in Nova Scotia in the 1970Ís, tilt-up wall panel construction has become
the construction method of choice for concrete buildings in several
Atlantic provinces, thanks to recent opportunities in school construction
and the spur of a competitive marketplace.
Experience
gained by a handful of Halifax and Dartmouth-area companies in tilt-up
design and construction has provided the base from which tilt-up's popularity
has extended into other areas of Nova Scotia as well as New Brunswick,
Newfoundland and Prince Edward Island. Its development in Nova Scotia
received a major boost in the late 1990's with the successful completion
of fifteen schools within very tight time frames. These schools, designated
P3 (Private Public Partnering) are owned and operated by the private
sector and leased back to the provincial government. The 1998 contract
called for twelve fully-equipped schools to be ready for occupancy in
just nine months, including both design and construction. Tilt-up proved
to be unique in its ability to meet this time line. Up to that point,
brick and block construction, together with a few examples of precast
concrete, had been the common methods of school construction, all requiring
between one and two years to build and equip a school. Following this
success, six more schools plus an addition to a seventh school were
built in record time across Nova Scotia in 2001, ready for the first
day of classes in September and despite one of the worst winters for
20 years. This marked the first time in the province's history that
any government owned school had been built using tilt-up construction.
John
Connely, marketing director of the Atlantic Provinces Ready Mixed Concrete
Association (APRMCA), estimates that some twenty-five schools have been
completed in Nova Scotia using tilt-up construction. The schools are
among an estimated 400 buildings that have been completed in Atlantic
Canada in the past thirty years covering a wide range of use and occupancy.
Applications have now expanded beyond low-rise industrial to include
nursing homes, theatres, retail developments and a five-storey, award
winning apartment building. Connely also cites the early competition
between tilt-up contractors as a key factor in its development, with
contractors such as B.D. Stevens Limited, J.W. Lindsay Enterprises Limited
and Rideau Construction Inc., all now drawing on a wealth of experience
and expertise to develop new tilt-up applications.
 Tilt-up
concrete method being used to construct a new building for solar panel
manufacturer Helio Research at the Burnside Industrial Park in Dartmouth,
N.S.
Speedy construction
Tilt-up is certainly fast. Aggregates & Roadbuilding
visited a commercial project in Halifax consisting of a 1 858 m2 single-storey
retail building having a job completion schedule of just three months.
From the first day of pouring concrete, the floor slab was completed
within one week, the walls all cast and tilted into place within one
month and the roof structure completed one week later. Another project,
this time a 929 m2 job in Moncton , N.B., was completed in a similar
time frame of just thirteen weeks.
These experienced contractors emphasise that
careful planning of wall panel casting layout and lifting sequence is
essential to take full advantage of the tilt-up's potential. A well-planned
job will fully utilise crane time, capacity, and reach to minimize the
number of crane moves and avoid any time-consuming multiple lifts of
individual panels. Panel size is only limited by the cost and availability
of suitable cranes, with the tallest panel cast to date in the region
being 27.92 m high. Connely points out that the construction sequence
of a tilt-up project is the reverse of a conventional building so that
the installation schedule for underground items such as storm and sewer
connections has to be adjusted accordingly. On a pre-engineered job,
for instance, the floor slab is often placed after the building's shell
is complete, unlike tilt-up where the floor slab is placed immediately
after the footings to provide the necessary casting surface for the
wall panels. Once on site, double checks on the accuracy of line and
level, thorough cleaning of the floor slab before panel casting, checks
on the accurate fit and location of joist pockets, and the precise placement
of lifting and bracing inserts are just some of the elements of a safe,
fast, quality job.
Curved wall panel construction is demonstrated by J.W. Lindsay Enterprises
Ltd. for the Helio Research building.
Mel Fiander, APRMCA president, points out that
no special materials or equipment are required for tilt-up. The concrete
typically used for wall panels is a conventional 28 MPa mix that meets
class F2 exposure requirements. The floor slabs mix can incorporate
40 mm aggregate to help reduce shrinkage and thereby minimise curling
and cracking of the concrete. In designing the floor slab, the overall
objective is to provide a smooth and uninterrupted casting surface having
a minimum of joints and visible surface cracks. As a result, sawed joints
are avoided wherever possible and there are recent examples of slabs
being completed with a jointless finish. Both wall and floor panels
are reinforced, with the structural section of wall panels typically
175 mm thick to withstand the lifting stresses encountered during construction.
The thickness of the floor slab is adjusted to suit local ground conditions
and the slab usually contains chaired wire mesh in the upper 25 per
cent to further control cracking. Concrete pumps are often used to access
both the floor slabs and wall panels and where floor slab space is at
a premium, the panels can be stack cast up to six deep. Here, successive
panels are cast on top of the previous panel once its concrete has reached
the required minimum strength, usually after a curing period of just
24 hours. The panels are then tilted and lifted into position after
a four to five day curing period. If a project schedule dictates working
through the winter months, curing is aided by building polythene sheeting
and wooden frame shelters over the slabs and space heating with propane.
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| Only
part way through the next day, the building takes shape as a Demag
AC 180 crane lifts the wall panels into place. Three of the wall
panels will also contain integral solar panels. |
Looking forward, tilt-up's future seems assured as new applications
and creative designs continue to appear. Lindsay's Enterprise's Laurence
Smith has found that tilt-up projects are moving away from its warehousing
base and going to structures with architectural features such a curves,
cornices and wider openings. According to Thane Stevens of B.D. Stevens,
virtually any building can now be completed using tilt-up and points
to the Bedford Baptist Church as a recent example. Here, the company
used tilt-up to complete an addition with a floor area of 1 95 m2 and
panel area of 465 m2. The panels included triangular tilt-up roof wall
sections and a cast-in 13 mm face brick external finish designed to
match the existing building. 
Patton apartment
building in Truro, N.S. built in 1994 by B.D. Stevens Ltd. At 18 m,
it is the tallest tilt-up building in Atlantic Canada. In 1996, it received
the Tilt-Up Concrete Association's Achievement Award. Photo
by John Connely
Contractors are also refining the construction
process to shave more time off tilt-up's already impressive completion
schedules. At the South Colchester School project in Brookfield, N.S.,
Rideau Construction utilised a Manitowoc 4000W crawler crane to tilt
and lift wall panels weighing up to 40 tonnes each. The crawler crane
was used in preference to a mobile crane following its successful performance
on the recently completed Shanex Health Care Management in Sydney N.S.
At 20 000 m2, the Shanex facility is the largest tilt-up project ever
completed in Cape Breton. Rideau's Donald MacDonald noted that the crawler
crane provides far more flexibility in terms of casting bed locations
and allows old casting beds to be reused. In addition, wall panels can
simply be carried to their proper location instead of the multiple pick-ups
sometimes required by a static crane. Finally, the crawler crane speeds
up panel completion by allowing more panels to be under construction
at any given time.
 Ecole
Beaubassin, built by Rideau Construction Inc., is one of 25 schools
in Nova Scotia built using the tilt-up method.
Where the building application calls for insulated walls, sandwich panel
systems are popular, and eliminate the need to add conventional insulation
after the wall is in place. The Owens Corning PinkCore XPS rigid foam
insulation and connector tie system, for instance, was utilised by Rideau
at both the South Colchester School job and the Shanex facility. Here,
the sandwich panel consisted of a 150 mm thick reinforced structural
component, connected to a 52 mm thick (R10) Type IV extruded polystyrene
insulation, and a 52 mm thick exterior concrete lift incorporating architectural
reveals (grooves) and coloured surface coatings. This design has eliminated
moisture transfer and the resultant potential for mould growth, while
providing effective sound insulation and a stable internal temperature.
Another popular, new tilt-up forming technique utilises Eco-Block Insulated
Concrete Forms (ICF's), with the panel from one side of the Eco block
system embedded in the plastic concrete of the wall panel. These expanded
polystyrene (EPS) forms have furring strips every 203 mm to allow the
attachment of wood or aluminium siding, brick, stucco, and stone on
exterior surfaces, or drywall or plaster on interior surfaces.
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What
is tilt-up?
Atboro House, designed
by Ruitenberg Inc., and built by J.W. Lindsay Enterprises Ltd.,
features 60 tilt-up concrete wall panels including some curved
panels which is unusual for tilt-up. The project is located alongside
Highway 111 at the south end of Burnside Industrial Park, Dartmouth,
N.S.
Tilt-up
is a construction method where the walls of a concrete building
are cast as horizontal panels at the jobsite, typically using
the finished floor slab as a working surface. After a specified
curing period, these wall panels are then tilted and lifted by
crane into their final position in the structure. Once in position,
the panels are temporarily braced until they are tied into the
building's roof and floor system and become an integral part of
the completed structure.
Most of the work on a panel is completed
while it is in a horizontal position, including the addition of
reinforcement, boxing out of openings for windows and doors, and
the addition of architectural features such as reveal lines. Bond
breaker is applied to the floor slab, prior to pouring the panel,
to prevent any sticking between floor slab and panel.
In its simplest form, a completed tilt-up
building incorporates plain concrete wall panels into a box structure.
Beyond that, an almost infinite variety of concrete forming, insulation
methods, curves, surface treatments and architectural finishes
are now available. Overall, tilt-up is said to be a safe, fast,
simple and economical method of construction that has been extensively
used for one-storey buildings and successfully adapted to multi-storey
applications.
After its first recorded North American
application in Illinois in 1908, tilt-up became popular in the
mid-1970's for low-rise commercial applications such as warehouses
and distribution facilities. An estimated 200,000 buildings have
been completed to date in the United States and Canada market
using tilt-up construction methods, involving some 14 million
panels with a combined area of 47 million m2. This market is reported
to be running at 4,000 buildings annually, involving 15 million
m2 of wall and 1.5 million m3 of concrete. Overall tilt-up project
completion totals for 1998 were 38 per cent higher than 1997,
which were in turn 25 per cent higher than 1996. In terms of market
segments, about 65 per cent of the tilt-up applications are currently
for industrial/commercial or institutional (ICI) buildings, 25
per cent are for offices, and the remaining 10 per cent for other
applications.
In terms of size, tilt-up buildings typically
have floor areas ranging from 1000 m2 to 6000 m2, and 8 metre
high wall panels weighing between 20 and 40 tonnes each. Current
reported records for tilt-up projects stand at a project floor
area of 160,000 m2 and wall panels 27.92 m high. The overall panel
size record goes to panels with an area of nearly 169 m2 (9.14
m wide by 18.47 m high) and weighing 140.95 tonnes.
Today's experienced contractors have
built on these origins with tilt-up's portfolio now expanded to
including school, office, retail, government, institutional and
residential buildings as well as other applications. Here in Canada,
tilt-up's utilisation varies widely across the country and is
concentrated on the west and east coasts. At least 2500 tilt-up
projects have been completed in British Columbia since the 1970's,
mostly in the Lower Mainland, where tilt-up accounts for about
75 per cent of light industrial applications. Some 125 to 150
projects are now being completed in B.C. every year, with applications
now extending into two, three and four storey office buildings,
movie studios and multiÆstorey mini-warehouses. Local records
include a project with a floor area of 56 000 m2 and a number
of others with wall panels up to 18 m high. On the east coast,
over 400 tilt-up projects have been completed to date and tilt-up
is rapidly expanding into the other Atlantic Provinces from a
well-established Halifax and Dartmouth, Nova Scotia base. Alberta
has seen some use of tilt-up, with about 50 projects completed
to date although this number looks set to climb, given recent
renewed interest. Across the rest of the country, only a limited
number of tilt-up projects have been completed to date, particularly
in the populous provinces of Ontario and Quebec, although interest
levels are generally increasing here as well.
In addition to its speed of construction
tilt-up, is said to offer a number of other advantages compared
to other structural designs such a steel frame or brick and block.
Tilt-up produces a very tight structure and is popular in applications
where durability, security, and thermal performance are important.
Its solid concrete walls are load bearing, while the method also
provides the opportunity to integrate both the insulation and
surface finish into the wall panel as a composite (sandwich panel)
unit. After the structural work is complete, tilt-up offers numerous
ways to customize the final appearance of the building through
differing surface textures, panel design and colour variations.
Cost
The economy of tilt-up lies in its speed
and simplicity of construction and, according to the Portland
Cement Association, tilt-up construction results in the lowest
first cost in most cases. The method is said to offer overall
economy by utilising readily available local labour and materials,
while its speedy construction minimises delays and delivers early
occupancy. These immediate construction cost savings are supplemented
during the life of the building by reduced operations and maintenance
costs. The Tilt-Up Concrete Association reports that less heating
and air conditioning will be required for a tilt-up building as
the thermal mass in concrete reduces both heating and cooling
loads.
As a final bonus, the durability and
performance of tilt-up buildings is usually reflected in stable
long-term property values.
References
American Concrete Institute (ACI) committee 551, Tilt-Up concrete
construction. Atlantic Provinces Ready Mixed Concrete Association
(APRMCA), Tilt-Up construction project sheet. Tilt-Up Concrete
Buildings, Portland Cement Association. Tilt ÆUp Concrete Association.
WSB Engineering, Burnaby B.C.
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December 2002
issue
Aggregates
and Roadbuilding Magazine
4999 St Catherine Street West. Suite 315
Westmount, Quebec H3Z 1T3
Tel: (514) 487-9868 Fax: (514) 487-9276
EMail: rocktoroad@sympatico.ca
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