If you’ve been to an old city like New York, DC, Chicago, etc, you’ll see lots of very tall buildings made with bricks. These buildings seem to be very straight and square even though they are dozens of stories high. How did the bricklayers keep everything so straight and square as the building went that high? Anyone who has done something like build a brick wall or column knows that it’s pretty easy for things to get sloped or twisted as the bricks are laid down. You have to do something like hang a string and use levels along the way to ensure the structure stays nice and straight. That works for things that are just a few feet high, but I can’t see those tricks working on a 500’ building. Hanging a string that blows in the wind and using 6’ levels aren’t going to cut it for that height. What tricks did those bricklayers use to ensure the building ended up straight from the ground to the top?
You’d be astonished as to how well a skilled user can use things like plumb bobs, water levels, transits, and bubble levels, and by the kind of precision you can achieve with analog instruments.
They might have a brick skin but they will be steel skeletoned, that was how it became possible to construct very tall buildings.
Optical surveying levels were good enough.
I can remember not too long ago (in the 1990s) walking past skyscraper construction sites in Chicago and seeing workers using plumb bobs and bubble levels. It’s amazing what a skilled craftsperson with good tools can do.
Traditional masonry construction lets you put essentially one row of stone or brick on at a time. A mason is always checking the set in relation to the courses immediately below and adjacent, and overall checking is also carried out using a variety of plumb bobs and squares. You start right so you can finish right.
The first skyscrapers - castles and cathedrals - benefited from a class of literate, rationally inclined polymaths who travelled extensively to learn from each other when that was definitely not the norm.
You can get a excellent sense of medieval and pre-modern building technology in the finer details of Pieter Breughel’s Tower of Babel, although its the least straight and square building ever envisaged.
At the time a tapering tower would have also been understood as being an even harder and far more complex challenge to build outside the straight line or regular geometry. Engineering forces were understood by training and rules of thumb, but it required so much over-engineering to cover possible unconsidered stresses, which made buildings far more massive and chunky, which in turn added unknown stresses …
Of course, the ones that fell down aren’t around to demonstrate that it doesn’t always work. For older works, the famous flying buttresses of Notre Dame were not in the initial design, but were added as the weight of the vault started to force the walls outward. The Leaning Tower of Pisa was altered several times in construction to try to bring it to vertical with little success.
The tallest brick building is only 214ft tall. The Monadnock building in Chicago.
It is quite a remarkable building. But its six foot walls at the base are an indication of the limits of using brick.
Brick is heavy and it becomes uneconomic to build higher.
So the engineers would never get the chance of trying out that 500ft plumb-line.
Taller buildings became possible once the steel makers perfected the Bessemer process for the mass production of steel and it became cheap enough to use as a building material. I guess a steel frame is easier to measure than a pile of bricks.
That’s because the bricks are a façade; they’re not load-bearing. Remove them, and the building still stands. (On further thought, I suppose it’s not completely true that they’re not load-bearing: the bottom bricks still have to support the weight of all the bricks above them.)
But it wasn’t always that way. In some (old) buildings, the walls are “pure” brick, and hence load-bearing. There’s a restaurant near me that was built in the 1880s, and the walls are made with two or three columns of brick.
The ability to create level building sites and structures goes back a long way.
Then, laborers excavated and leveled the foundation. No one is sure of the exact method, but they were extremely exact – the base of Khufu’s pyramid is level to 2 centimeters (less than an inch).
There is a YouTube channel called Cutting Edge Engineering Australia where the guy does videos of him working in his machine shop solo and working on heavy equipment repairs. It is not construction like the OP is asking about but he needs to do precision work and I only ever see him using analog tools. Some of the tools are high precision calipers and stuff like that but still…doing it all by hand. Yet, he achieves amazing precision (e.g. using a blow torch to heat something so it expands and then putting something inside it so when it cools that item is now firmly locked in the piece…I get the physics but there is not a lot of room for error there but he manages it).
The gravitational field of the Earth is really very consistent. (You need very sensitive tools to measure variations, and variations in direction are even more subtle.)
So any device that provides a measurement based on the gravity field is starting from a very good base.
Plumb bobs and water filled tubes remain accurate over large distances. You can level over a huge area to an accuracy of a few millimetres with a tube full of water. And if you hang a plumb bob off the top of a building the only thing that will stop it measuring to a few millimetres over the entire height is wind loading on the line.
In principle a tall building will be ever so slightly wider at the top, but that is being slightly silly. Similarly, levelling ground with a water filled tube gets you a surface matching the curvature of the Earth. Unless you are building a gravity wave detector you mostly don’t care, or you actually need that curvature.
It does seem like magic the first time you ever get to think about it, but that’s how the metal rims on wooden wagon wheels were made [among other things], so a pretty mundane technology not so long ago.
Not sure which Egyptian pyramid they’ve determined it was used on, but at least one of the biggies was probably levelled by creating a large pond, and then the top of the water was used as the datum and they would remove all stone to X.XXX cubits below that plane [accuracy to the thousandth of a cubit - that’s how good they were].
It’s also surprisingly easy to get a square structure to actually have a square base. Measure the diagonals. If they are equal, it’s square. That’s it.
The Great Pyramids also have a bit of an oddity that the ratio of the base perimeter to the height of the pyramid is highly precise multiple of π. Some people think this proves that the ancient Egyptians had some fantastic understanding of π to a much higher precision than anyone else (because aliens! or something). The truth is much simpler. It’s because if they were measuring in cubits, they just made a wheel that was a cubit in diameter and counted wheel rotations. We still use the same thing today. You can measure the length of the sides extremely accurately just by counting wheel rotations and you can make sure the base is square by measuring the diagonals with the same wheel.
I walk by that building quite often and I have been in it many times. Lovely building inside and out.
The walls at the base are very, very thick but it is not obvious unless you point it out to someone.
I have always been amazed at how clean the brick-work is.
I heard a rumor that a few other buildings like this were built and many years later were found to be super difficult to demolish (extremely robust).
As the wiki article explains, the south half of that building uses steel framing. A beautiful and fascinating building. Used to get my hair cut by a barber there.
Because an addition used steel that means the brick isn’t structural?
Indeed. Builders and masons had a history of many long centuries of honing their craft to get things plumb and level. And those who got it wrong, the building did not stand.
As mentioned, in the case of steel-framed brick-skinned skyscrapers, the “skin” would partly support itself and would commonly even be doing so one floor at a time, that wall being in turn held there by the steel/concrete structural members.
Hmmm… I think we’ve had enough good factual answers for a bit of levity in the answer to the thread tite…
