On August 19, a large 400 ton crane arrived on site. Over a period of four days the crane lifted more than 120 concrete planks into position. The planks form the new church sanctuary floor. The resulting floor, gently sloped for better visiblity, is now evident to those watching the construction cam. After grouting the seams between the planks, the next step will be to pour a smooth concrete top layer across the entire floor.
A very large crane, dubbed “Big Grizz II”, rolled onto the site last Thursday. The mobile crane, which is road capable, took a half day to setup. The crane, worth more than $4 million, travels with other trucks that carry the necessary counterweights, pads and outrigger accessories necessary to do the job. Once fully assembled, the crane boom was easily able to handle the job. The boom reached the farthest corners of the church (~130′) and was able to lift the heaviest planks, which weigh 16,000 pounds each (8 tons)!
Using computer controls, the experienced crane operator carefully lifted the planks off a parade of large flat bed trucks that delivered 5 to 15 planks each. The planks, some as long as 45′, were carefully lowered to two waiting trades people who guided the planks into position. Each plank rests on a steel beam and/or ledge in the foundation wall. Using extremely long pry bars, the workers slid the planks snugly up against one another.
Our planks were poured off-site to our exact specifications. Each 12″ thick plank is a hollow core design. That means there are openings inside the concrete that run the length of the plank. The planks also have steel rebar inside the concrete, near the bottom of each plank, to add additional strength. Each plank has a slight camber, or curvature, that counter balances the load that will be placed on top.
The planks are joined together with steel clamps and cement grout. Each plank is slightly beveled along their length. Even though the bottom of the planks are touching, this “V” shape between the planks allows cement grout to be placed from on top. This cement locks together the planks and also secures the “C” shaped steel clamps that are placed between many of the planks.
The past week has seen above average temperatures for late August in Michigan. The team has diligently put the new floor in place under difficult circumstances. For the rest of this week a different crew of cement workers will prep and pour (weather permitting) the remaining lower level ramps and stair well floors. Then, the final step will be to pour a 2-3″ topping over the entire main sanctuary floor. This will provide the smooth finished floor surface onto which tile and carpet can be laid.
A 400 ton crane, Big Griz II, arrived on site. As it says: “Cranes are cool!”
One truck after another arrived with the ~120 concrete hollow core planks.
Most of the planks were lifted directly from the trucks, with lines on both ends.
The crane towers above the site as it positions the first plank in the floor.
The crane operator guides the planks over and between the steel columns.
The expanded town square and organ chamber are completed first.
Workers who make the final placement talk by radio with the crane operator.
The view from the back narthex doors looking towards the front chancel.
The hollow core openings and steel rebar (double dots) are visible on each end.
The chancel is to the right, looking south into the sanctuary.
The shorter planks form the ramp and aisles on each side of the sanctuary.
A pot of cement grout is lifted by crane to the workers below that fill the seams.