How did Notre Dame's wooden roof exterior last for 800 years?

I read that the exterior part of the wooden roof of the Notre Dame cathedral was the original from 800 years ago. I could see how internal structures might last that long but how can an an exterior, even with whatever liberal use of waterproofing materials I’m guessing they used, last so long?

The exterior of the roof was lead cladding, not wood. The lead sheeting protected the wood underneath.

Just like modern houses have a wood roof, protected by asphalt shingles or adobe tiles on the exterior.

CNN has a good piece about the roof:

Lead cladding has two definite advantages, provided that the dead weight is not a concern:

Lead’s toxicity helps to reduce the occurrence and growth of fungi and bugs that can lead to deterioration in timber.

Lead’s malleability makes it easier to ensure a properly weather-proof seal. A soldered or crimped copper-clad roof can still have small openings or splits and slates or tiles will all allow moisture to penetrate and work its magic on the wood.

There are two more advantages:

The lead frame and roof are fire-resistant.

The lead roof on the spire also provided lightning protection the the rest of the structure.

There’s lots of ancient wood around in Europe in old buildings. Basically if you keep it dry, and keep the bugs out, wood will last a very long time.

I also suspect that parts of it - perhaps all of it – have been repaired and replaced over time.

Certainly parts of it have been, but apparently quite a bit was documented as really being that old.

Dendrochronological analysis of the wood used in the central pillar of the Hōryū-ji pagoda in Japan, widely acknowledged to be the oldest wooden building existing in the world, estimates it to come from wood felled in 594 AD. The adjacent kondō building uses wood felled before 670 AD, and it’s estimated that about fifteen to twenty percent of the original seventh century Kondo materials is left in the current building.

Under good storage conditions, wood can last for a very long time. The oldest known wooden sculpture is made from a log about 11500 years old. It was preserved in a bog. Many wooded items from ancient Egyptian tombs both survive as well as maintain much of their paint and applied ornamentation.

The structural timbers made from a whole mature oak forest were original. But almost surely some parts and pieces of roof backing-boards and lead exterior cladding would have been patched up over time. Then the tall steeple only dated to the 1840s so it would be reasonable if putting that up would have required altering some of what was already there if only to anchor it properly and re-seal where it met the prior roofline.

Indeed. I used to work in an office that used to be a medieval barn (probably 13th or 14th century). We wanted to hang some lights from the original oak beams, but just could not get a drill into the timbers, they were tougher than concrete.

Much of the roof of Salisbury Cathedral, widely considered to be the pinnacle of early English church architecture and the largest and most complete 13th century stone building in Britain, is original and has survived 750 years of weather and neglect. Much of the oak used in the roofs of the eastern chapels, the earliest part of the cathedral, was felled in spring 1222 in woods around Dublin, making the roofs some of the oldest in Britain. Others came from local trees, cut down at the same time.

The cathedral’s own website has a good page (mostly in French) on the history of the roof, with lots of excellent photographs. One relevant point it makes is that only the wood in the roofs of the nave and the choir was medieval - the beams above the transepts were replaced in the nineteenth century by Viollet-le-Duc.

Thanks for the link which does have a lot of great photos. It’s very interesting to see how the wood roof support tied into the stone towers and seeing the vaulted ceiling below.


Even less than that. I know of some people who had the contract recently to dispose of a mining camp from the 1940’s; they said the fir use had hardened so much, you could not drive nails into it. I shudder to think of 800-year-old oak’s properties.