I’ve read a few news articles that proclaimed charitable donations to Notre Dame may not be enough to cover the cost to rebuild the damaged cathedral roof. One article on Bloomberg news stated, “The cost might well run as high as 8 billion euros”.

I think it’s time some news sources engage with a professional architect, engineer and cost estimator before writing these articles. 8 billion Euros is enough to spend an astronomical amount to repair the damage!

One World Trade Center is the most expensive building built in the U.S. It cost $4 billion. It measures 3.5 million square feet (SqFt).

Some sources are saying the Notre Dame cathedral roof repair may cost more than $8 billion. The Notre Dame roof, as closely as I can determine from online data of the building, measures about 50,000 SqFt.

Just think about that.

I’m stretching my thought process to come up with a rough estimate that would cost as high as $250 million. Frankly, my rough estimate is quite a bit lower than that, and that would still be far more costly per SqFt than the most expensive building in the U.S.

I haven’t yet seen an architect / engineer estimate of the total area of the roof. I traded some emails with an architect who thought total area was 25,000 SqFt. I searched online and come up with potential area of roof at 50,000 SqFt. Here I’m using 50,000 SqFt.

I have not seen any other realistic cost estimates. But, the most expensive roof covering and roof structure I’ve ever estimated was less than $100/SqFt (in 2019 dollars).

My order of magnitude estimate (OME) (very general), for a unique, complex structure and premium roof covering could be $500/SqFt. Portions of this roof need to be quite ornate and also the estimate must include a ceiling structure. For a historical and rare roof plus inside work let’s double that estimate to $1000/SqFt. That’s 10x the cost of the most expensive roof I’ve ever estimated / built.

$1 billion would provide for $20,000/SqFt.

$8 billion would provide for $160,000/SqFt!

Even if my OME is 10x too low and I make a 10x adjustment, cost would then be $10,000/SqFt for a total cost = $500 million. That’s 100x more expensive than the most costly roof I’ve ever estimated. Frankly, I can’t come up with any conceivable scenario where it could cost that much.

footnote: 8 billion Euros is currently about $9 billion US dollars