Modified and connected foam wall structures and methods for making them are described. The wall structures include a frame, a foam panel attached to the frame, a foam layer disposed in a cavity defined by the frame, and a structural adhesive. The structural adhesive may be disposed in at least one of: (A) an aperture located within the foam layer, and (B) an aperture located between the foam layer and a frame member. In some cases, a cured structural adhesive is located between connecting members of adjacent foam wall structures.