Oxford Dining Hall Beam
Nickels holding up a dollar. Hurry up and wait. If it were not for the last minute, nothing would get done.
These phrases are to be avoided in scheduling construction projects. The Critical Path Method (CPM) is an algorithm for scheduling a set of project activities. Think about a wall of movable Post-it Notes representing all the activities in a project (including submittals, approvals, fabrication duration, deliveries, construction, and installation for each trade). Each Post-it Note contains details as to the activity’s duration and the activity’s predecessor. It is often the case where dozens of activities are all waiting for the same predecessor activity, such as the delivery of an item. These predecessor activities become critical. Aligning these critical activities is the value of CPM. The activities along the critical path have no float time and create scheduling milestones. A Gantt chart is a bar chart with the activity line items displayed as duration bars along a timeline and can provide a visual representation of the CPM.
A mantra of construction scheduling is the 7 Ps - Prior Proper Planning Prevents Pitifully Poor Performance (with variations of Pitifully). When learning about scheduling in college, one of the best examples I heard of Prior Proper Planning involved the repair of timber beams in an old building.
New College, founded in 1379, is one of the oldest colleges in the 39-school confederation of the Oxford University system in England. The great dining hall of New College is similar to the dining hall of Harry Potter’s Hogwarts (without the floating candles). As the story goes, in the 1860s, substantial insect damage was discovered in many of the two-foot square, forty-five-foot long oak beams of the dining hall roof framing spanning the width of the building. At the suggestion of a Junior Fellow, the College Council called the College Forester in the hopes that any of the endowed forests scattered across the country would have mature oaks to harvest for new beams. The College Forester discovered that when New College was founded, a grove of oaks had been planted to eventually replace the large timber beams of all the college’s buildings and that generations of College Foresters had been waiting 500 years for the request. Quite a representation of Prior Proper Planning. The question remains if new trees had been planted in the 1860s after the harvested trees were made into beams.
In my search for the details, I reached out to New College. No original building accounts survive for the medieval dining hall. In 1533, the interior and roof framing had been altered by the installation of a ceiling and wall paneling. In 1786, the ceiling was reconfigured to be flat, again altering the roof framing. Because very little trace of the medieval timbers in the dining hall remained at the time of the 1863 restoration, the new roof structure was redesigned in a form that was sympathetic to what the original might have been. The timber for the new roof of the dining hall came from a forest that was acquired by the college in 1441, seventy years after the original construction of the dining hall. The official response from New College is that the story is a myth.
However, as it takes hundreds of years for oaks to mature fully, it could be said that any managed forest has Prior Proper Planning at its core when its trees are planted and coppiced. For centuries, the large wood masts of ships were harvested via forest management. So even though the replacement beams of the New College dining hall roof are a myth, the truth is in the intention of the story. Planting trees a century ahead of time follows the Prior Proper Planning Prevents Pitifully Poor Performance mantra, and is a great example of the Critical Path Method of scheduling.
About the Author
Mr. Centurelli provides consultations in the areas of structural analysis, including root cause, scope of damage and value of loss of residential and commercial property. You may contact Tony for your forensic engineering needs at firstname.lastname@example.org or (860) 285-8000.
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