This monograph contains an investigation on corrugated paper honeycomb as a lightweight core material in environmentally friendly load-bearing sandwich elements. In the first part of the text, analytically and experimentally determined honeycomb material properties, such as thermal conductivity, elastic moduli as well as shear and compressive strengths, are presented. The second part is concerned with an environmentally friendly cementitious impregnation, which renders the paper honeycomb water- and fire-resistant and improves its mechanical properties in compression and shear. The third part features a comparison between measured and predicted buckling strengths of sandwich members with corrugated paper honeycomb cores. In the final section of this publication, structural applications for impregnated and unimpregnated honeycomb in buildings are suggested.