Keen, who played a key role in Sir John Egan's client-led Rethinking Construction initiative, is to become deputy director of building at the group, which owns department stores and the Waitrose supermarket chain. He joins on 8 March.
Keen was trained as a quantity surveyor and has been with Tesco for nearly 10 years. He said he will relish the new challenges provided by working on a wider range of buildings and with a wider range of professions.
At Tesco, he liaised mostly with contractors, but at John Lewis he will also be expected to work with mechanical and electrical contractors and designers of in-store layouts. He will also gain experience of working in department stores as well as new-build.
Keen will work closely with John Lewis' director of building services John Carpenter, and with head of building Gary Matthews. He is expected to eventually take over from both of these.
His appointment will ease Matthews' workload, who has been suffering illness – although Matthews is likely to continue to work on large-scale, one-off projects, including the new John Lewis outlets at Bluewater in Kent and in Glasgow.
However, Keen will take on day-to-day work, liaising with outside contractors and consultants and taking responsibility for the 11 Waitrose stores that are due to start on site this summer.
Carpenter said Keen is expected to fit in well at John Lewis because some of the ideas he has introduced at Tesco, such as select lists of contractors, are already standard practice at the client.
He believes Keen, a promoter of prefabrication and integrated design and construction, will be able to help John Lewis on its tight city-centre sites.
His appointment was also motivated by John Lewis' aim of making greater use of prefabrication to counter potential skills shortages, improve the quality of production and to reduce noise on its sites, as parts have already been hammered together in the factory.
John Lewis works most closely with Bovis, Sir Robert McAlpine, Laing and Wates nationwide, and uses smaller firms, such as Geoffrey Osborne, for work in separate regions.
The client spends £150m a year on construction and owns £1bn of land and property. Its portfolio includes a hotel in the Lake District, a country club in Sussex and a castle in Dorset.