The clay ovens and leather tanneries appear to date from the 12th-16th Centuries.
Housing developers called county historians after they found mortar and flint footings for wooden buildings.
Andrew Tester, project officer for Suffolk County Council, said: "We know a lot about the centre of the town, but not about this part."
The precise location of the site is not being publicised to protect the dig.
The Warren Map of 1740 showed the area to be fields - so this is the first evidence of previous development.
They think these were to store lime putty which was used to create mortar, plaster and lime-wash for building.
Mr Tester said: "It's very exciting. Hopefully we'll be able to find more of these barrel wells and find out definitively what they were used for."
Around 50 cattle horns have been found.
They were probably a waste product of the leather industry, although they were used as drinking vessels and as an alternative to glass in lamps when cut thinly.
Mr Tester said most big houses would have had an oven for malting barley for brewing.
"Water was less appetising whereas beer is naturally sterilised, so it was good for you," he said.
The archaeological team expects to spend a month at the site before the housing developers begin their work.
Items such as coins and buckles will be removed, but the clay ovens will be filled in and built over.
Alongside the clay ovens, the archaeologists have found a series of sunken barrels.
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