I know the Basilica of the Nativity in Bethlehem quite well, although I haven't been there for over 30 years. It was very common in early centuries for large basilicas to have wooden ceilings. It turns out that the one at Bethlehem is one of the oldest. This interesting article is from vaticaninsider.
An Italian study carried out on the Basilica’s wooden beams has revealed that the cedar was carved between the 6th and 7th centuriesGiorgio BernardelliMILANIn the next few days, as is the case every year, all eyes will be on the Basilica of the Nativity in Bethlehem. But the deeper the studies on this ancient church go, the more surprises it seems to have in store. This is what transpires from a report published yesterday in the last edition of the Journal of Cultural Heritage and on Terrasanta.net.The report presents the results of a long study carried out on the Basilica’s ceiling; the part of it that is in worst condition and is in urgent need of restoration. The good news is that the website of the Custody of the Holy Land states that the work “should in all probability begin next spring.” This is important because every time it rains, water leaks into the building and risks causing some serious damage.
Aside from this, the article contains some interesting information about the tattered wooden trabiation which needs repairing. The study led by the scientific team coordinated by Professor Claudio Alessandri, a professor in the department of Engineering at the Italian university of Ferrara and carried out in collaboration with the National Research Council of Italy and Trees and Timber Institute (CNR-IVALSA), has revealed that at least part of the wooden ceiling is made of cedar beams that date back to sometime between the 6th and 7th centuries. This would therefore have been the wood used in Byzantine times to rebuild the Constantinian basilica which had stood there previously. This dated back to the 4th century and was destroyed by the Persians. The discovery indicates that those beams are among the most ancient in the entire Mediterranean. This confirms the uniqueness of this Christian church, which was proclaimed a UNESCO World Heritage site last year.
The existence of beams this old does not, of course, mean that the ceiling was never once restored in fourteen centuries. Indeed, a close analysis of the wood showed that not all the beams are made of cedar, some are in larch and others in oak. But while oak is indigenous to the region, larch is not. Historic documents show that this type of wood came from the Eastern Italian Alps. This confirms another historical fact relating to the Basilica: the larch, which was needed for the restoration work that took place in the 15th century, was donated by the Republic of Venice.
The wood used on the Basilica’s ceiling reveals one other detail regarding the long history of this building, which stayed in tact for so many centuries. It turns out that the oak beams used for the Basilica’s restoration in 1848 in fact come from Anatolia. This too was a gift: it is the same wood used to build the small Muslim aedicules dotted around the Hagia Sofia Basilica in Istanbul. In an interview with Terrasanta.it, the CNR’s Dr. Mauro Bernabei, said “the Ottoman administration of the time promoted the restoration of a Christian Basilica using the same wood as that which was used to build Muslim places of worship: I see this as a tiny symbol of dialogue and peace, linked to the Basilica of the Nativity…”