Born in Mainz, Johannes Krahn studied architecture from 1923 to 1927 at the Technische Lehranstalten Offenbach.

He continued his studies 1927 to 1928 at the Kölner Werkschulen as Meisterschüler of Dominikus Böhm, who interested him in building churches.

[3][4] His church building St. Wendel, Frankfurt (1957) has been compared to Le Corbusier in terms of materials and flow of light.

[2] In 1965 Krahn created a variation on the interplay of stonemasonry, glass and concrete of St. Wendel in St. Martin, Idstein.

Among his last projects was in 1974 the design of St. Aegidius in Bonn-Buschdorf [de], realized after his death by his son Johannes Krahn in the firm Krahn-Lorenz-Sauer, Frankfurt am Main, in 1978 to 1980.