The disclosure describes, in part, techniques for designing, fabricating and installing structural caps with a core and composite sleeves to be coupled to structural members of a foundation, such as an installed radial array of batter angled micropiles. These structural caps with sleeves are lightweight and, thus, more portable to difficult-access sites. Once at the sites, operators may fixedly couple these caps to the micropiles or other structural members to form a foundation for a structure to be installed at the difficult-access site.