underbuild

verb2

1. •
   To perform insufficient construction on a building or in an area; build below a specified requirement or standard.

   • Appellee was obliged to overbuild, rather than underbuild, the appellant's telephone line for the distance of these six spans for the following reason [...] — 1903
2. •
   To build beneath another structure; provide a foundation or support for; undergird.

   • The two eastern arches have been underbuilt for the sake of strengthening them. — 1900