Upgrading non-traditional housing
Early non-traditional or system built housing was not built to today's thermal standards and some prefabricated units were only ever intended to be temporary accommodation which, while much appreciated at the time, were not intended to have a long life.
Common issues and queries you can face

Concrete decay
These are often concrete structures which show signs of decay after a long period of time.

Movement
System built prefabricated units are often subject to relatively high building movement. Due to the construction methods this movement often continues throughout the life of the property, driven by thermal cycles.

Condensation problems
Low thermal resistance of the wall construction often means that these properties are plagued by condensation problems. Where a steel frame was used with a mixture of steel cladding and masonry, condensation is a big problem and in the extreme can cause failure in the steel structure.

Uneven surface for rendering
These construction methods often feature infill panels. These may not offer a flat, in-plane surface suitable for traditional rendering.