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such a respected architect and had performed so
well on other projects for the wool guild that he
clinched the commission. In 1420 his audacious
design was approved on condition that he share
the plans with his rival Ghiberti.
Sabotage and Success
That same year a memorandum was drawn
up listing the project’s structural principles.
Brunelleschi confirmed the dome would have
a double shell, and he included the dimensions
of the structural rings. He stressed once again
that he would build it without any external sup-
port, but exactly how remained unclear. Today
no documentation survives that explicitly ex-
plains his engineering behind the dome. Much
of what is known comes through observation
and analysis of the finished work.
Early on in the construction of the dome,
the disappointed Ghiberti and his faction used
various stratagems to sabotage Brunelleschi’s
proposal. They accused him of deviating from
Fioravante’s original project and of committing
structural errors in the building work. They even
grew so desperate that they complained that the
dome’s design made the cathedral interior too
dark. None of these controversies succeeded in
holding back the project, though. After the base
of the dome reached the agreed-upon height
in 1426, approval was granted for the work to
continue without any supporting structures.
In 1429 cracks caused by the weight of the
dome were beginning to appear in the cathedral,
but Brunelleschi fixed them with reinforcements
of iron and wood. Slowly, layer by layer, the dome
rose, with no need of any scaffolding. Drawing
on his experience, Brunelleschi designed hoists
to facilitate the work. These involved innovative
uses of cogs and shafts, and they were equipped
with various speeds and a reversible gear. Years
later, Brunelleschi’s devices would be studed and
sketched by another brilliant Renaissance mind,
Leonardo da Vinci.
Brunelleschi had a radical
proposal: He would build
the dome without using any
support systems at all.