British English has many harsh words for rough work done where proper work was possible.
Cowboy builder: A builder who does poor, dishonest work. Other tradesmen of this kind are called cowboys too.
A botch job: Work done badly and carelessly.
Jerry-built: Built cheaply and badly.
Shoddy: Badly made, or done with little care.
To cut corners: To do something in the easiest or cheapest way, at the cost of quality.