Skip Navigation
Page Background

Residential Code Requirements

This section contains general residential building code requirements. Please refer to the Building Codes for more detailed information. This information is intended as a guide and does not relieve the applicant from complying with all applicable code requirements.
New homes and existing homes undergoing additions constituting more than a 50% increase in square footage are required to install type NFPA 13D residential sprinklers. 

**Changes are effective 11/02/2020**

Design Loads - 2018 International Residential Code

  • Ground snow load - 25 psf
  • Wind speed - 115 mph
  • Attics with storage - 20 psf
  • Decks - 40 psf
  • Balconies - 40 psf
  • Rooms (other than sleeping) - 40 psf
  • Sleeping areas - 30 psf
  • Passenger vehicle garages - 50 psf (2000 lb point load over 20 sq. in area)
  • Handrails - 200 lb concentrated lateral load
  • Soil bearing capacity - 2,000 psf

Foundation Walls

  • Continuous wall footing is required except that one-story buildings may use piers
  • Foundation piers may be stone, brick, or concrete block
  • Accessory buildings less than 400 sf require footings a minimum of 12” below grade
  • Over 400 sf require footings a minimum of 30” below grade
  • Piers and all other footings must be placed below the surface of the ground and shall not be less than 30 inches (bottom of footing) and all joints must be securely cemented together

Mortar Mixture

  • Not weaker than 1-2-3 ½ and all mixture wet, but not more than 6-3/4 gallons of water to one bag of cement of 94 pounds


  • Shall not rest upon masonry within 8 inches of the ground
  • There shall interpose between the wood and the masonry a solid continuous layer of solid block or cement mortar at least 4 inches thick, or a hood along the edges of the masonry
  • No wood within 4 feet of the ground shall be allowed to come in contact with piping, or other objects unless they have been fitted with metal shields to block the shelter tubes of termites

Wood Framing

  • Must be spaced 16 inches on centers
  • Must be bolted to foundation with bolts of not less than one-half inch in diameter at 6 feet maximum centers
  • Minimum embedded to a depth of not less than 8 inches in placed concrete
  • Less than 15 inches in width of all wall supported thereon
  • Pressure treated joists < 18” to ground
  • Provide double joists under oversize bathroom tubs
  • Provide 15 ½ heel at roof truss bearings for R-49 insulation installation
  • Provide collar ties or structural ridge at framed roofs less than 3 ½ in 12 pitch
  • Deck construction must comply with all specifications provided in the Deck Construction Guide

Wood and Door Openings

  • Must be double studs
  • Must have double headers
  • All headers must be set on top of the studs, and must be set on edge
  • For all single window and door openings, not exceeding 48 inches, the headers shall not be less than double 2x4 supporting one floor or roof
  • For all twin openings not exceeding 72 inches, the headers shall not be less than double 2x6 supporting one floor or roof
  • All triple openings not exceeding 8 feet, the headers shall not be less than double 2x8, and not exceeding 10 feet, not less than double 2x10 supporting one floor or roof.  All headers must be braced at the top

Roof Framing

  • Roof sheathing panel nominal thickness from 3/8 inch to 7/8 inch. Reference: 2018 IRC Table R503.2.1.1(1)
  • Eave overhang shall not exceed 24 inches
  • Rake overhang shall not exceed 12 inches
  • A readily accessible attic access opening not less than 22 inches by 30 inches shall be provided to any attic area having a clear height of over 30 inches
  • Access to the attic opening containing appliances shall be provided by a permanent or pull-down stairway in all new construction

Moisture Protection (Foundation)

  • Subsoil drains are required for all dwellings with basements, cellars, crawl spaces, or floors below grade and must be located inside and outside of the foundation.  Weep holes are required with hollow block, maximum 48 inches apart
  • Foundation walls of habitable rooms located below grade shall be waterproofed with membranes extending from the edge of the footing to the finish grade line.  The membrane shall consist of either 2-ply hot mopped felts, 6-mil. Polyvinyl chloride, 55-pound rolls roofing or equivalent material. The laps in the waterproofing membrane shall be sealed and firmly affixed to the wall
  • An access crawl hole 18 “by 24” shall be provided to the underfloor space. Vents to be located per 2018 IRC, Section 408
  • Siding 6 inches minimum above finish grade.

Moisture Protection (Roof)


  • Ice barrier is required to be installed for new construction & re-roofing works with asphalt shingles, metal roof shingles, mineral-surfaced roll roofing, slate & slate-type shingles, wood shingles & wood shakes. Reference: 2018 IRC R905.1.2
  • Drip edge is required for new construction & re-roofing works, shall be provided at eaves & rake edges of shingle roof. Reference: 2018 IRC R905.2.8.5

One (1) hour fire resistance construction for walls

  • Structures less than 5’-0” from property line
  • Residential dwelling equipped with sprinkler system but less than 3’-0” from property line
  • One (1) hour fire resistance wall assembly;
  • 5/8 inch Type ‘X’ gypsum board each side of stud wall or equivalent
  • Shall be installed from the foundation up to the underside of roof sheathing

Sprinkler System

  • New construction, Demo and Rebuild structures
  • Additions constituting more than 50% increase in square footage inclusive of an unfinished basement

Accessory Dwelling Unit (ADU)

  • ADU without free-flowing access (i.e. case opening) from attached principal dwelling shall have a wall separation with minimum One (1) hour fire resistance construction
  • Access door in-between shall have minimum 45 minute fire resistance construction
  • One (1) hour fire resistance wall assembly;
  • 5/8 inch Type ‘X’ gypsum board each side of stud wall or equivalent
  • Shall be installed from the foundation up to the underside of roof sheathing

Plans on file (POF)

  • Requires a Maryland registered Engineer or Architect signed & sealed construction drawings 


One and Two Family Dwellings Code Requirements

Bedroom window

Minimum window required - 
Minimum net clear opening -

Minimum net clear opening height -

Minimum net clear opening width -

Maximum still height -

5.7 sq. ft

Minimum width -

3 feet

Minimum clear width -
Minimum headroom -
Minimum tread -
Maximum riser -

3 feet
6 ft 8 in
3/4 inches
GuardrailMinimum height + required at walk surfaces over 30-inches above grade or stairs with 4 or more risers


RailingMinimum height
(required at least one side of stair)
34 to 38-inches
PicketsMaximum clear spacing between pickets4-inches
Working space around electric equipment

Minimum width -
Minimum in front -

Ceiling height

Habitable rooms -
Other areas -
Under beams & ducts -

7 ft, 0 in
6 ft, 8 in
6 ft, 4 in

Non-absorbent gypsum baseboard around shower & bath areas

Emergency Escape
And Rescue Openings
At least one Emergency Escape and Rescue Opening is required for basement and habitable attic 
Fire stopping

All duct chases, bulkheads, laundry chutes, metal flues, tub traps, and all shafts at each floor

Fuse box

Do not locate fuse box in clothes closets

Smoke detectors

One (1) required on each level, plus one (1) in each bedroom and one (1) outside each sleeping area. Each shall have internal battery back-up plus being hardwired.

Exterior stud walls

2x4 or 2x6, P.T. sole plates in contact with masonry or concrete

Wall coverings

Drywall - ½ inch
Paneling -
(Maximum smoke density - 450
Maximum flame spread - 200

Habitable rooms

Minimum area -
Minimum horizontal dimension -

70 sq. ft.
7 feet
Garage SeparationAttached garage separation from residence and attic minimum 1/2" gypsum board.  Habitable rooms above garage minimum 5/8" Type "X" gypsum board.  
Non-combustible floor sloped to overhead door with 4" minimum elevation to residence floor.  
Minimum 20 minute or 1-3/8" solid wood door with self-closer.  No openings into sleeping areas.


































Table of Building Envelope Requirements*

Windows and Insulation 
Window U Factor0.35
CeilingR-49 (or R-38 uncompressed)
Exterior WallsR-20 with 2x6 stud wall
R-13 + R-5 with 2x4 stud wall
Floor over unheated space (i.e. crawl space or above garage)R-19
Basement Wall R-10 continuous insulation (horizontal + vertical) applied to exterior or interior walls or R-13 insulation required in all stud walls
Slab PerimeterR-10, 2 feet concrete slab / foundation (horizontal or vertical) or at exterior foundation perimeter (vertical)
Crawl Space WallR-10 or R-13
  1. This table is based upon the International Energy Conservation Code, published by the International Code Council.
  2. U-factors are MAXIMUM acceptable levels.
  3. Insulation R-values are MINIMUM acceptable levels.
  4. This table applies to single-family, wood frame residential construction. For steel framed wall construction or high-mass wall construction. Refer to Chapter 5 of the IECC.
  5. “Window” refers to any translucent or transparent material (i.e. glazing) in exterior openings of buildings, including skylights, sliding glass doors, the glass areas of opaque doors, and glass block.
  6. Window U-factor must be determined from a National Fenestration Rating Council (NFRC) label on the product.
  7. Window area % is the ratio of the rough opening of windows to the gross wall area, expressed as a percentage.  Up to one percent of the total window area may be exempt from the U-factor requirement.
  8. Opaque doors are not considered glazing (or windows) and must have a maximum U-factor of 0.35. One exempt door allowed.
  9. The code requires that windows be labeled in a manner to determine that they meet the IECC’s air infiltration requirements; specifically, equal to or better than 0.30 cfm per square foot of window area (swinging doors below 0.50 cfm) as determined in accordance with AAMA/WDMA 101/I.S.2 (ASTM E 283).
  10. R-2 shall be added to the requirements for heated slabs.
  11. Floors over outside air must meet ceiling requirements.
  12. R-values for walls represent the sum of cavity insulation plus insulated sheathing, if any.
  13. Prescriptive packages are based upon normal HVAC equipment efficiencies.

All Electrical, Mechanical, and Plumbing Construction must be done in accordance with the adopted Anne Arundel County Codes and subject to field inspection.