The firm has dominated the annualised rankings of contracts won for more than a year but this month slid down the table to fifth slot.
Laing O’Rourke has taken its place at the head of the league, chased closely by Morgan Sindall and BAM.
Mace takes the prize for most work won in May after confirming a £330m deal with Land Securities for the Victoria Circle project in London.
Among the other big jobs secured last month, Shepherd won a £65m deal for developer Kitewood to build 460 flats & 4 shops at Capitol Way in Edgware.
BAM Nuttall has a £75m job for SSE to build a substation in Moray.
United House took the £60m scheme to turn the Alfa Laval Site on the Great West Road into housing for Carlton Properties and Farrans landed a £40m school project in Ellon for Aberdeenshire Council.
The tables can be found in the Contracts Spy section of the website listed at the top of this page.