1 November 1996
recommended by EPA.
9. DESIGN REQUIREMENTS.
a. New Construction. Design requirements consist of passive barriers to seal radon entry routes and
active sub-slab suction systems to remove radon gas from the soil under floor slabs and around below grade
walls. The objective of both passive and active design strategies is to reduce radon entry to interior spaces.
Specific design requirements, based upon facility priority and potential radon concentration, are listed in
table 1 by letter codes. The letter codes are described below and indicated on the details shown in
Table 1. Design requirements for radon prevention
0 to 4 pCi/L
4 to 8 pCi/L
8 to 20 pCi/L
20 to 200
over 200 pCi/L
(0 to 148
(148 to 296
(296 to 740
(740 to 7400
(1) Passive Barriers, Letter Code A. Passive barriers are required for facility priorities 1 through 4
and for all potential radon concentration levels. Passive barriers include 6 mil polyethylene sheet in crawl
spaces and under floor slabs on grade, capillary water barrier below floor slabs on grade, dampproofing or
waterproofing and protection board on below grade walls, sealants in all joints in floor slabs, below grade
walls and around all pipe and conduit penetrations. Provide solid courses in hollow masonry walls to
prevent gas passage through the internal voids. Joint sealants will be selected and installed according to
TM 5-805-6 and CEGS-07920. Polyethylene sheets will be lapped 12 inches and sealed with adhesives or
pressure sensitive tape and sealed at foundation walls with mastic. Capillary water barrier will be according
to CEGS -02221 except that capillary water barriers will be installed without regards to site conditions.
(2) Sub-slab Suction Systems, Letter Codes B, C, and D. Sub-slab suction systems consist of 4-
inch diameter perforated PVC pipe laid in the capillary water barrier below floor slabs which are used to
create negative pressure fields under the floor. Provide a suction stack connection, using non-perforated
PVC pipe, stubbed through the floor slab and capped. The suction stack should be near the middle of the
under slab pipe run and be located where it can be extended through the building roof with minimum
changes of direction. Requirements for letter codes B, C, and D are identical except for the spacing for
under slab pipe runs. In structures with basements or other below grade spaces, connect the sub-slab
piping to the foundation drainage system so that the negative pressure field is extended to the earth side of
below grade walls. Where the foundation drainage has gravity outfall, provide an interior suction stack and
a water trap. Where foundation drains discharge to a sump, seal the sump cover and prove a suction stack
connection to the sump; large buildings will require additional suction stacks remote from the sump.
Building sites with seasonally high ground water may require a high water sensor at the suction stack
connection to shut off the suction fan. Radon gas is water soluble. It is reasonable to assume that a