The property of osmotic swelling of a hectorite clay suspension in water is exploited for dispersing it in a polymeric foam matrix. This green route eludes the surface modification of clay as well as the mediation by organic solvents for clay dispersion during foaming. The route follows the initial swelling and partial delamination of clay galleries by water molecules, followed by further dispersion in an oligomeric isocyanate foaming component, before conducting reactive foaming. A nominal mass fraction of clay provides an effective barrier, restricting the gas phase mass transport in the foam. Electron microscopic investigations show that clay particles are preferentially located on the lamellar part of the microscopic foam cell, rather than on plateau borders.