by Katie Daniel | April 18, 2018 3:13 pm
By Nicole Laidler
Tilt-up concrete has been around since the turn of the 20th century, when architect-contractor Robert Aiken used it to construct several buildings in the American Midwest. In an early claim to fame, Thomas Edison employed the tilt-up method to build concrete houses in New Jersey, some of which are still standing today. (For more information, read christineadamsbeckett.com/2012/04/03/thomas-edisons-beautiful-failure.)
Tilt-up concrete fell out of favour during the Great Depression when putting people back to work was the priority, but regained popularity during the post-World War II construction boom. The development of mobile cranes and advancements in concrete also solidified its reputation as an efficient and low-cost building method. By mid-century, it was being used almost exclusively for warehouses and other big-box structures.
Tilt-up remains a good choice for large-box structures, but the method also offers the flexibility to deliver a wide range of complex and creative projects. Today, tilt-up represents about 10 per cent of the total nonresidential building market in the United States. No figures are available for the Canadian building market, but the Tilt-up Concrete Association (TCA) estimates that the industry as a whole is growing at around 20 per cent each year. (The Tilt-up Concrete Association [TCA] is the international nonprofit trade association for the global tilt-up concrete construction industry. It provides training, certification, and other resources for tilt-up construction throughout North America. To learn more about the association, visit www.tilt-up.org.)
Although fairly new to Ontario, more than 200 tilt-up projects have been completed across the province, including 37 school buildings, multistorey office buildings, warehouses in excess of 9290 m2 (100,000 sf), and the Toronto Premium Outlets shopping mall in Halton Hills, Ont.
The basics of tilt-up construction
Tilt-up construction is similar to a traditional barn-raising. Regardless of the project type, the process begins with the preparation of the jobsite and the pouring of the concrete floor slab. Footings around the slab are also installed in preparation for the panels.
The concrete panels are cast either on the floor slab or on an adjacent slab, depending on the building’s footprint.
Standard dimensional lumber is used to create panel forms, which act like a mould for the concrete by providing the panels’ exact shape as well as openings for doorways and windows. The steel grid of reinforcing bars is tied into the form, and inserts and embeds for lifting the panels and attaching them to the footing, roof system, and to each other are also installed.
Tilt-up panels are built from the outside of the wall to the inside of the wall, so any exterior cladding or formliners are placed on the slab before concrete is poured into the forms. Insulation is also encased into the building panels—a feature providing tilt-up buildings with true edge-to-edge insulation, thereby eliminating thermal bridging.
Complete buildings are often lifted in a matter of days. Panels are temporarily braced until the structural connections of the building have been completed.
The building is now ready for any exterior wall finishes such as sandblasting, painting, or staining, if required. Joints are caulked, with typical panel joints consisting of a 20-mm (0.78-in.) gap between panels filled with insulation, backer rod, and caulking to prevent water penetration. Any imperfections in the wall surfaces are patched. At this point, the roof system can be installed—trades can then begin their work inside the building.
Advantages of tilt-up construction
Although tilt-up requires careful front-end planning to ensure smooth co-ordination of the design with the construction process, it offers significant benefits to the finished structure.
Speed of construction
Since much of the tilt-up process—including the exterior, insulation layer, and structural layer—is completed simultaneously, the construction time of a tilt-up project can be reduced significantly. Another factor contributing to the speed of tilt-up construction is the fact 90 per cent of the work is completed at ground level, reducing the need for working at heights.
Tilt-up panels can be insulated using several different methods, depending on the project specifications and building energy codes. The most common method is the insulated sandwich panel, which can serve both a structural and thermal function. As the name suggests, a sandwich panel consists of two wythes of concrete—the interior loadbearing layer and exterior façade—with a layer of rigid foam insulation, typically extruded polystyrene (XPS), in between.
This combination creates an airtight envelope with a thermal mass, minimizing heating and cooling peaks inside the building. Smaller and less costly mechanical systems can often be used, resulting in significantly lower operating costs over the lifetime of the building.
As energy code requirements become more stringent and with heating and cooling costs typically representing around 30 per cent of a building’s annual operating costs, many are taking note of the energy-efficiency offered by tilt-up construction.
Tilt-up construction offers some sustainability advantages related to the materials employed. Concrete, ready-mix, and rebar are available locally, reducing carbon emissions for transport. Additionally, concrete and the wood used for panel forms are easily recyclable, which reduces the impact on local landfills.
Safety and durability
Since the building material is the same, a tilt-up structure provides similar resilience and durability to a structure constructed using precast or traditional site-cast concrete. These buildings can withstand earthquakes, wind, and rainstorms, and are virtually impenetrable to rodents and insects.
While tilt-up is most closely associated with warehouse and other industrial structures, it offers almost endless design possibilities.
As a fluid building material, concrete can easily be formed into curved walls or other unconventional shapes as designed.
Tilt-up also offers a wide variety of exterior finishes, allowing architects to design a visually distinctive building even when budgets are tight. Esthetic features can include staining or painting, exposed aggregate, textured surfacing, relief panels, embedded brick veneer, and almost limitless formliner options.
Tilt-up construction has been embraced south of the border and is quite prevalent on Canada’s East and West Coasts. Ontario, though, has been slower to adopt the method. One of the reasons is the misconception tilt-up processes cannot be done during the winter.
Last year, Tilt Wall Ontario won the 2017 TCA Achievement Award for Educational Buildings for its work on Ottawa’s Broadview Avenue Public School—a project that was successfully completed on a tight schedule throughout the winter months.
“When it comes to winter casting, we simply cure with ground heaters and curing blankets. Curing the concrete is actually easier to control during winter construction than it is in the hot summer sun,” explained Len Overbeek, co-founder of the installing firm, Tilt Wall Ontario.
The 6967-m2 (75,000-sf) elementary school consists of 117 site-cast panels of up to 100 m2 (1080 sf). Edward J. Cuhaci and Associates Architects employed a wide variety of tilt-up finish techniques to create a vibrant, attractive building that is suitable for an established urban neighbourhood.
Broadview’s exterior finishes include red brick veneer, colourful architectural forms, stain, and glass panels. Unique formliners also allowed the architect to incorporate children’s artwork and the handprints of all 950 students into the exterior design.
A method with few limitations
Virtually any size of building can be a tilt-up project. Buildings with footprints less than 55.7 m2 (600 sf) and exceeding 185,806 m2 (2 million sf) have all been constructed using the method—multistorey structures are very common. Panel size can be limited by the size of the jobsite and the cranes available for lifting.
Small building sites—such as in a congested downtown—can present a challenge since tilt-up requires adequate floor space or land for casting beds as well as access for cranes.
In Ontario, Overbeek said finding a design team familiar with the method can also be difficult. Proper upfront co-ordination is vital, since making changes to the panels once they have been cast is not simple. Considering project economics, factors that favor tilt-up construction are: its ability to deliver projects quickly, smaller construction crews, minimized long-term maintenance costs, and potential energy savings.
For the end user, the inside of a tilt-up concrete building feels just like its traditional counterparts—whether it is a school structure, office building, retail centre, place of worship, industrial warehouse, or personal residence.
|ONE ENTHUSIAST’S TILT-UP HOUSE|
|Last spring, Len Overbeek, co-founder of Tilt Wall Ontario, built a multistorey tilt-up house in Oxford County, where he now lives with his wife and children.From the outside, the 269-m2 (2900-sf) home is indistinguishable from a conventionally built residence. Inside, Overbeek incorporated several unique design elements including stamped and polished concrete. The front entrance hall features a painted finish that looks like marble.“Living here, you cannot tell it is a concrete home. The walls I painted look just like drywall,” said Overbeek.
Although the cost of a tilt-up home is around 10 to 15 per cent higher than a traditional build, Overbeek said the thermal mass of concrete and the home’s continuous insulation provide energy savings of around 30 per cent.
Lot size is one constraint to residential tilt-up construction, he explained, so the method is best-suited for custom homes rather than single-family suburban residences.
“Since I started working with tilt-up, I always thought that this is how I would love to build a home someday. Knowing the energy-efficiency, durability, and flexibility of concrete, there really was no other alternative for me,” he said.
Nicole Laidler has more than14 years of experience writing for a wide range of publications for corporate and nonprofit clients. Laidler holds an MA in journalism from Western University and is a member of the Canadian Association of Journalists and the International Association of Business Communicators. She lives in London, Ont., and can be reached at email@example.com.
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