Homing in21 March 2019
Julian Champkin looks at how diferent approaches to house building—both innovative and traditional—have driven different approaches to lifting materials around the world.
More than half the housebuilders in the UK increased the rate at which they built new homes last year and predict a further rise over the next 12 months; even so, they expect to fall short of the government’s target of 300,000 per year. So says a survey for consulting company McBains.
There are variants of this story of housing shortage and demand around the world. Year-on-year construction activity in China grew 6.1% in Q4 2018: not the doubledigit growth we once used to see but still not small; in the US, too, house-building is booming.
One building method that may be gaining ground, in part because of these shortages, is modular building, otherwise known as offsite construction or, in the old days in the UK, as pre-fab housing. In Asia and in the UK governments are encouraging it on grounds of speed, economy and as a response to a shortage of skilled labour.
Nor is it as weather-dependent as traditional bricks-and-concrete construction: since it needs only a few days on site rather than many weeks, frost or rain is far less disruptive. Advances in materials have vastly improved the quality of such homes to equal or exceed those of brick-built homes. Factors that have held back prefabrication in the UK in the past were that mortgage lenders were unwilling to lend on such houses and insurers were unwilling to insure them. Both of these are now being addressed.
Indeed one UK insurance company, Legal & General, has set up its own factory, in Leeds, which delivered its first units in December 2018 and which it says will produce 3,500 modular houses a year— which will equal or exceed the output of familiar leading house building companies.
Lifting requirements for modular houses are slightly different. Whole buildings, or sections of buildings, are ready-assembled in a factory and transported by truck to the site, where they need to be lifted into place.
Telebooms so far seem to be the crane of choice for the task. Construction company Richard Kölch & Sohn used two Tadano all-terrain cranes on a project in Germany, though only one was needed at a time. The elements of the house— nine pieces of ready completed wall and roof sections— were transported from factory to site in a five-hour journey on a ‘road train’, a two-axle truck plus a three-axle trailer. The final access road to the residential area was too narrow for this, so the company’s brand-new Tadano ATF 60G-3 transferred the pieces of the house onto a small three-axle truck with a superstructure custom-designed to take modular house components.
Each section presented a load of between 3t and 4t; the maximum size was 11m x 3m, and a 5.1t counterweight was used. Kölch is intending to use its ATF 60G-3 mainly as a ‘taxi crane’ for jobs in the construction of pre-fab houses.
At the site itself a slightly larger Tadano ATF 90G-4, with 90t capacity and 50m reach, placed the elements directly onto their final positions.
In Britain, Ilke Homes has opened a factory in Knaresborough, Yorkshire, to produce eight homes a day, each ready-fitted with bathrooms and kitchens. Outside walls can be finished (again at the factory) with stone or brick sections to fit in with local styles. One such house was recently temporarily erected, as a demonstration show-house for delegates to a conference for property professionals, in Manchester’s Barbirolli Square.
A 150t teleboom operated by Ainscough was used for the job. The home was fully-assembled and ready to live in within one day. “This type of construction is a game-changer,” says Gary Rathburn, manager of Ainscough Crane Hire’s Manchester depot.
Self-erectors have been taking over some house-building business in recent years, especially in older cities where space is at a premium. Liebherr’s L1 series is an example: “They are ideal for single dwellings because they don't need much space and are very easy to assemble, directly next to the building,” says Hans-Martin Frech, marketing director at the Liebherr Biberach factory. “The slewing radius of the L1-24 is just 1.9m, and its footprint can be reduced to less than 4m, which means that there is often no need to close roads. For an apartment block, the K series is the better choice because of its longer jib and bigger lifting capacity.” The Liebherr 81 K.1, for example, has a maximum radius of 48m and capacity of 6t. But even the L1-24 can have a reach of 27m, so if access is limited it is well able to lift materials over the top of a building to the other side. “Both crane types have higher capacity than knucklebooms or aluminium boom truck cranes,” says Frech. Both have fast erection times.
The L1 can be erected by a single person without difficulty. The K series needs only a very small rigger team.
And for urban and residential areas Liebherr’s MK series of mobile self-erecting tower cranes is also being used for house-building and gives the added advantage of electric power on the crane.
The carrier has a normal diesel drive-engine, but once on-site, the electric powered crane gives not only economy but also zero emissions and almost-noiseless operation, which can allow longer periods at work. “Users understand this more and more,” says Frech.
“The MK cranes combine the mobility and flexibility of a mobile crane with the range and speed advantages of a tower crane.”
Aluminium-boom cranes have been widely used in Europe for many years. After some time, their virtues are now being appreciated in the UK as well. Klaas and Böcker are the main manufacturers.
Alan Crane is sales director of Kranlyft, UK distributors of Klaas cranes, and he is vocal for the benefits of aluminium for housebuilding.
“Aluminium boom cranes originally had one main purpose, which was roofing” he says. “When they first came to the UK they were used for a wider range of jobs, but now probably roof trusses are their main application, because that is what they are meant for. Indeed Klaas came from a housebuilding background and the design of all their cranes stems from that.”
“For example, there is a framework on the side of the crane that can carry a roofers’ platform, or an additional slung basket, or an attachment for skips.”
Klaas make both truck-mounted aluminium-boom cranes and trailer cranes. “The most popular trailer crane is the 1.5t K23-33 TSR,” says Crane. “It has self-levelling outriggers. On-site it is drivable very very accurately by remote control, it can fit into really tight spots and can be fully extended, to 34.1m, in three to four minutes.
And, since it is a trailer crane, it has very small axle loadings.” Among Klaas truck-mounted models the K750 can lift 1t at 14m and 0.5t at 21m, with 360º rotation. “Again it has low axle loadings and outrigger point loadings, so hirers like them: they do not damage things as an all-terrain would,” says Crane.
Mounted on a Mitsubishi Fuso carrier it weighs less than 7.5t, which means that in the UK it can be driven without an HGV licence.
“We are expecting that many operators will replace existing truck cranes which fail the new MOT regulations with these,” he says.
The biggest of the range is the K103 RSX, which has a 3t capacity with an option for 6t.
This again has the working range to pass a load over the top of a building; its control system allows for two remote stations, so one operator can stand one side of the building to send the load up, and when it passes out of his line of sight he can hand control to a colleague on the other side for lowering it.
The other big name in aluminium boom truck cranes is Böcker. After 50 years in the crane business, Alan Stowell retired – then got bored and came out of retirement and bought himself another crane to serve house-builders again. It is a Böcker AK35/3000 on a MAN carrier.
“It is a great concept, a unique bit of kit,” he says. “It is light weight, the boom is aluminium, not big heavy steel, and has that extra bit of length that makes the difference.” (The Böcker AK35/3000 has maximum extension of 35m.) “It is ideal for roof trusses. The remote control is one of the things that does it for me. You can be up on the roof with everybody and few words need to be spoken, because you don’t need a banksman, you can control the crane from up there. That eliminates an awful lot of risks.
“It is so narrow on the slew; that in London is ideal because there is no need for road closures while you are working. You do not have two or three metres out at the back with the counterweight on it; the Böcker has just half a metre.
And the outriggers can be on the pavement side of the job, so you are just 2.5m wide, and that again is brilliant for London.”
“I can lift more than 1t at 12m. Occasionally I have thought of moving up to the Böcker 44, which does 1t at 22m, which would give more scope; but then it is human nature to always want the one that is just that little bit bigger and really there hasn’t been a job in the past two and a half years that the 35 could not do.”
They handle roof trusses differently in America. Straightboom truck cranes are the machines of choice. Mike Heinrich is director of sales at National Cranes, the boom-truck division of Manitowoc. “Two forms of them are commonly used,” he says. In standard configuration the boom is mounted behind the cab and facing rearwards during travel. In tractor-mounted configuration the boom is similarly mounted but faces forward, over the cab roof, during travel. National’s 680-TM has a 24.4m (80ft) five-section boom; its capacity is 18.1t (20 USt). “It will commonly arrive at a site not only loaded with ready-made roof-trusses resting near-vertically on a frame on the flat-bed, but towing a 40ft trailer similarly loaded behind it. The aim is to transport all the trusses for the house in a single load,” says Heinrich.
In many parts of the States the service goes further. To avoid double-handling the straight-boom does not unload its trusses to the ground. “It lifts them directly to roof-plate level” says Heinrich, “where the construction people can attach them straight away.
It is a standard service offered by truss-makers and expected by construction companies. The truck-boom cranes are owned and run by the truss manufacturers, not the construction people.”
Delivering direct to the roof-line assumes that the construction has got to the roof plate-readystage; and it is not universal. “It varies from place to place, even places not far apart. In Northern California it is standard. In Southern California it is not, and trussmakers unload to the ground and are not expected to get them any further. In Chicago both systems operate.”
“In Seattle, in the Pacific Northwest, you would use a 900A series 800e in Standard configuration. This has a 31.4m four-section boom. For a larger house, people might use the NBT40-1; this puts up wall sections as well.
“Demand for all these is generally steady but cycles with housing demand and the general economy” he says. “At present the housing shortage, especially in boom states such as California, is acute: employers are moving into the state and finding that they have to erect housing for their employees.
Accordingly, many are building multilevel apartment units, rather than single- or two-level houses, as the quickest and easiest way of doing it; bigger cranes are accordingly needed.
The NBT30H-2 is one of National’s biggest, with a 30USt capacity and a four-section 110ft (33m) boom.”
Outrigger designs can be A-frame, mounted behind the cab, or vertical. “The A-frame gives more flexibility in tight situations, such as in remodelling existing houses where trees and neighbouring properties can be in the way.”
As European-style use of aluminium booms is making headway in the UK, so Europeanand UK-style use of knucklebooms may be penetrating the US.
Palfinger’s PK 34002 SH knucklebooms have what they call HPSC-Plus Load detection system.
The cargo load on the truck can itself act as a counterweight while unloading the first elements of it, so load-chart reach for the earlier stages of unloading can be greater.
In practice, an operator filling in a construction trench on a building site would unload to the furthest distances required first, while his truck still has plenty of load onboard, then as his truck empties would cover the nearer sections of trench.
Eikenhout is a family-owned roofing supply company in Grand Rapids, Michigan, and until recently relied exclusively on telescopic handlers to deliver roofing shingles on-site. They then experimented with truck-mounted knucklebooms; and have now invested in a larger truck-mounted Palfinger PW310 knuckleboom with fly-jib. “With a bigger crane we have gained jobs, like three storey apartment buildings, that we otherwise would not have been able to complete,” said Erik Brooks, Eikenhout’s vice president of operations. “In comparison to my old telescopic handler, the knuckleboom offers more flexibility and maneuvreability because you have better access to the roof,” says his chief crane operator.
The tasks are similar worldwide. Preferences differ; but then why should they not? It makes for diversity and a more interesting world.