# Sec. 4-250. Foundations; Section R-404, Foundations and Retaining Walls

Codified through Bill No. CB-018-2026, adopted May 12, 2026, effective July 24, 2026. Source: Municode, Supplement 2026 Update 2. Editorial notes and legislative history omitted.

## Sec. 4-250. Foundations; Section R-404, Foundations and Retaining Walls

Prince George's County, Md., Code § 4-250 (2026)

(a) The following amendments, additions, and/or deletions are made to Section R-404 of the International Residential Code:

  (1) Section R-404.1.1, Design Loads. In addition to other applicable loads, the basement walls shall be designed for the at-rest pressure (lateral soil load) as described in Table 1610.1 of the 2021 International Building Code.

  (2) Section R-404.1.2, Design of Concrete Masonry. Design of concrete masonry unit (CMU) walls shall conform to the Building Code Requirements for Masonry Structures (ACI 530/TMS 402) Chapters 1, 2 and 3. Minimum horizontal joint reinforcement consisting of not less than two continuous wires each with a minimum cross-sectional area of 0.017 square inch (9 gage) shall be provided in horizontal bed joints spaced not more than every second course vertically. For basement walls subjected to lateral earth pressure, minimum vertical reinforcement shall consist of one No. 5 rebar (ASTM A615 grade 60) spaced not more than sixteen (16) inches (for nominal 8", 10" or 12" walls). Cells having vertical reinforcement shall be filled with concrete or masonry grout meeting the requirement of ASTM C476. Vertical steel reinforcement shall be placed not more than 2 inches from the inside face of the walls.

  (3) Section R-404.1.3, Design of Concrete Walls. Design of concrete walls subjected to lateral earth pressure shall conform to the Building Code Requirements for Reinforced Concrete (ACI 318) Chapter 10. Minimum reinforcement in each direction shall not be less than that required by Chapter 7 (i.e. for ASTM A615 grade 60, No. 4@14" for 8-inch thick, No. 4@12" for 10-inch thick, and No. 4@10" for 12-inch-thick wall). For design of concrete walls subjected to lightly loaded lateral earth pressure (4 feet or less of unbalanced backfill) or concrete walls with insignificant stress components (for example, stresses reduced by mean of wall stiffeners) the ACI 318 Chapter 22 may be used to determine the amount of reinforcement required. Engineered wall design is acceptable for wing walls per ACI-318 code.

(b) For walls that are proposed to serve as floods walls, the permittee shall secure approval from the US Army Corps of Engineers prior to submittal to Prince George's County for building permit. The applicant shall submit evidence of approval.

(c) The following requirements shall be met for retaining wall permits, not including cantilevered retaining walls for basements, which are covered by the 2021 IBC, Chapter 18.

  (1) The Height of a retaining wall is measured from lowest ground elevation on the lower or bottom side of wall to the highest elevation on the top of the retaining wall structure, at any given cross section of the wall.

  (2) Soil investigation is required at a minimum rate of one soil test boring per 100 linear ft of the retaining wall length.

  (3) Timber retaining walls are not allowed.

  (4) In general, on residential developments, the height of retaining walls shall be minimized preferably to less than 6 feet, for ease of maintenance. This also applies to the cumulative height of tiered retaining walls.

  (5) Retaining walls shall be located on common homeowner or business park association parcels, to the maximum extent practical. Retaining walls shall not be located in the public storm drain or storm water management easements. Retaining walls shall not be located in the County public road right of way, except for abutment walls for bridges.

  (6) For Segmental Retaining walls (SRW) including Mechanically Stabilized Earth Walls (MSEW) higher than 2 feet, and other proprietary products, the applicant shall include in the permit submittal the manufacturer's information and specifications, and a valid evaluation report from a DPIE approved listing agency. The permittee shall submit an acceptance letter for the geotechnical aspects only of the wall design from the Geotechnical Engineer of Record (GER) if the GER is not the wall designer.

  (7) Declaration of Easements for Retaining Walls

    (i) Retaining walls and tiered walls with a cumulative height of 6 feet or greater are required to have a permanent easement in front of and behind the wall. The easement dimension shall not be less than 10 feet wide on the low side of the wall.

    (ii) On the high side of the wall, the easement shall contain the select backfill zone, including soil reinforcement including geogrids, tiebacks, anchors, and footings.

    (iii) The easement dimension on the high side of the wall shall not be less than 10 feet wide.

    (iv) Grading and retaining wall permit plans shall reflect the limits of the retaining wall easements and the horizontal extent of soil reinforcement, footing, and select backfill zone.

    (v) The following site elements shall not be located inside retaining wall easements:

      (aa) Buried utilities (except as noted in (9)(aa) and (9)(bb) below

      (bb) Building additions

      (cc) Porches

      (dd) Structures

      (ee) Pools

      (ff) Decks

      (gg) Stormwater management devices and storm drain pipe

      (hh) Trees

    (vi) The following site elements are permissible inside retaining wall easements:

      (aa) Storm drain outfall pipe located perpendicular to the wall, if there is no alternative but to penetrate through the wall. The storm drain shall have a drop manhole on the high side of the wall, and the storm drain pipe under the footing of the retaining wall shall be encased in an outer pipe sleeve that is at least 12 inches larger in size than the conveying storm drain pipe.

      (bb) Storm drain inlets and pipes necessary to capture the swale immediately above the wall. These storm drain systems must be designed shallow enough to be built above the soil reinforcement (not deeper than 2 feet).

      (cc) Sheds

      (dd) Fences - fence posts shall be located a minimum of 3 feet from the face of wall.

      (ee) Patios

      (ff) Pergolas

      (gg) Benches

      (hh) Sidewalks

      (ii) Trails

      (jj) Signage

      (kk) Landscaping (not including trees)

      (ll) Private roads and parking lots — guardrails and traffic barriers shall be provided and located between the wall and the roadway, a minimum of 3 feet from the face of the wall.

    (vii) Above features in (9)(cc, dd, ee, ff, gg, hh, ii, kk and ll) are only allowable within retaining wall easements if the Declaration of Easement language obligates the owner/maintainer of these features to remove and replace these elements, as may be required for wall maintenance or reconstruction.

    (viii) The retaining wall Declaration of Easement shall specify maintenance responsibility.

    (ix) The Declaration of Easement shall restrict future construction of unacceptable elements.

    (x) Retaining walls that span across multiple residential lots shall be maintained by the Homeowner's Association.

  (8) Retaining wall plans shall show wall drainage systems and select backfill behind the wall, filter fabric between the select backfill and adjacent soils, structural elements, and reinforcement type and size.

  (9) Retaining walls shall be designed to meet the minimum safety factor of 1.5 against sliding and overturning.

  (10) Retaining wall plans shall show in site plan view, wall profile view, and wall sections the extent of select backfill, soil reinforcement, filter fabric, and other pertinent information. The design professionals (structural, civil, geotechnical) shall fully coordinate select backfill and soil reinforcement with all site features.

  (11) Retaining walls shall be located with the toe of the wall a minimum of 25 feet from creeks, streams, and swales, as these locations have the potential for eroding and undermining retaining wall structures. The design engineer shall submit a scour analysis for streams and swales in close proximity to retaining walls. If the scour analysis requires, the retaining wall permit documents shall be designed with a foundation system capable of withstanding the scour, for example deep foundation system and/or armoring of the stream, as required.

  (12) Segmental retaining walls (SRWs), including the leveling pads, shall not be placed below the 100-year floodplain elevation, due to concerns with scour and migration of soil backfill.

  (13) For retaining wall permits, a global stability analysis shall be signed and sealed by a licensed geotechnical engineer and must be provided for the following conditions:

    (aa) Walls with cumulative height taller than 10 ft;

    (bb) Walls with cumulative height taller than 6 ft and with back slope steeper than 3 horizontal to 1 vertical;

    (cc) Walls on or adjacent to unstable soils, such as over-consolidated clay; or

    (dd) When deemed necessary by DPIE or the Geotechnical Engineer of record (GER).

    (ee) The retaining wall calculations shall achieve a 1.5 minimum factor of safety for global stability.

    (ff) The global stability analysis is also required for a series of tiered retaining walls, for which the cumulative height of all walls exceeds the heights described in (17) above.

  (14) Retaining walls shall be drained by a system that includes:

    (aa) Perforated drainage pipes at the toe of the wall. Toe drainage pipes shall be connected to a solid storm drain or discharge to grade;

    (bb) An upright drainage layer behind the wall façade that ties into the toe drainage behind the wall bottom. This drainage layer can consist of gravel or a prefabricated geo-composite if recommended by the design engineer;

    (cc) Filter fabric between the gravel and soil; and

    (dd) Perforated two (2)-inch minimum diameter PVC weep holes, through the wall, for the entire length of the wall, and at a maximum spacing of 20 feet.

  (15) Within the select backfill zone, the upper soil layer shall consist of 4 inches of topsoil and 12 inches of impervious clay soil or an impermeable geo-membrane below the topsoil. The purpose of this is to limit surface water infiltration into the select backfill zone of the retaining wall.

  (16) To prevent surface storm water from flowing over the top wall of wall, a swale is required immediately behind the wall. The swale may be located at least 12 inches behind the high side of the wall, with a depth of at least 6 inches. The swale shall have 4 inches of topsoil at the surface and 12" of impervious lean clay soil or an impermeable geo-membrane below the topsoil. If the length of land adjacent to and perpendicular to the wall is negligible, for example less than 5 feet wide, such that surface sheet flow down the slope and towards the wall is minimal, then the swale above the wall is not required. All concentrated flows shall be intercepted into a storm drain system and conveyed thru the wall.

  (17) If the groundwater elevation is 2 feet or less below the retaining wall leveling pad or is expected to rise seasonally to the bottom of the leveling pad or higher, a blanket drain is required below the retaining wall, near the bottom of the leveling pad.

  (18) If an identified water source such as groundwater or springs are located on the high side of a retaining wall, a drainage blanket and chimney drains at least 6" thick are required. The drainage blanket shall extend laterally from the wall to the chimney drain at a rising slope of 3%. The chimney drain shall rise to the elevation of the groundwater source, and shall have a heel drain pipe with a minimum four (4) inch diameter at its bottom. Blanket and chimney drains are also required if surface drainage runoff or subsurface water may otherwise flow to the wall, which frequently comes from unconfirmed or unidentified water sources. The blanket shall extend back from the wall to cover the entire select backfill and to reach the possible water source. The chimney height shall be seventy (70) percent of the wall height, with a heel drain pipe.

  (19) Soil reinforcement and/or other slope stabilization measures, such as caissons, piles, piers, deep dynamic compaction, or other means shall be shown to scale on the site grading plans in profile and plan views.

  (20) Retaining walls that retain multiple lots shall pass final inspection successfully before structures on all retained lots can receive final inspection.