Interior Finishing of Underground Areas

Article Type: 
Thursday, January 26, 2006

Summary & Standards
last revised Jan 27, 2006

Underground Finishing Summary below provided for general information purposes; current GHI rules supercede any abbreviated guidelines
GHI rules §X.B.7
  permit request type I, II
  neighbor consent not required
  Board approval boiler room renovation only
Prince George's Cty
City of Greenbelt
permit required
direct egress to exterior is required

Interior finishing of underground areas (boiler rooms, townhouse basements, masonry basements) requires careful consideration of construction details, to avoid future problems with water infiltration, fungal growth, and indoor air quality. This plan relies upon an interior perimeter drain and sump pump to eliminate infiltrating groundwater by drawing the level down to the perimeter drain, and minimizing moisture migration through living space walls by waterproofing from the exterior. The following details are required based upon use of the area:

  Boiler room living space Townhouse, masonry basement
detail above grade below grade below grade
6 mil polyethylene vapor barrier lapped 6" min at all seams and onto vertical walls, leakproof basement access door required required
perimeter drain at the designated elevation, forming a complete circuit inside the exterior walls, draining into a sump pit; sump pump expels water to exterior required just below the vapor barrier required just below the bottom of the floor support structure required below level of basement slab
venting for area below living space per code if crawl space, powered ventilation if storage  
waterproof exterior walls   required down to elevation of perimeter drain required down to elevation of perimeter drain