St. Louis County Department of Public Works
Division of Code Enforcement
HABITABLE RESIDENTIAL ADDITIONS
BUILDING PERMIT REQUIREMENTS
This guideline is intended to provide the homeowner/contractor with the basic information needed
to apply for a building permit to construct most simple residential room additions. For larger more
complex additions having several rooms and for additions including kitchens or basements, it is
recommended that the homeowner/ contractor also obtain a copy of St. Louis County's "SingleFamily Dwelling Checklist" to aid in the preparation of plans required for submittal.
1.
Fill out and sign application for a building permit.
2.
Submit four (4) separate copies of your plot (site) plan showing the following:
An accurate, legible drawing, drawn to scale that clearly depicts the dimensions and
angles of the property boundary lines.
The location of all building setback lines and easements.
The size and location of all existing structures on the lot (including the new
addition), the dimensions of the addition, and its distance from the lot lines and from
adjacent structures on the lot.
Grade shall be noted to slope away from foundation a minimum of a 6” drop within
the first 10’ or to a swale. Indicate present and proposed finished grades at each
corner of the addition in relation to the established first floor level. Direction of
drainage shall be indicated with arrows on the site plan.
Show location of existing on-site sanitary sewage disposal system and well if
applicable.
A wall of a room addition that is less than 3’ to the lot line shall be a one hour fire
rated exterior wall with no openings.
3.
Obtain zoning approval from the Department of Public Works, if an unincorporated area, or
from municipality. In municipalities site plans must be marked "Approved" and Municipal
Approval Form submitted with application.
4.
Submit four (4) separate complete sets of detailed building construction plans drawn to
scale and containing the following:
Foundation Plan @ 1/4" = 1'-0"
Floor plans @ 1/4" = 1'-0"
Building Elevations @ 1/4" = 1'-0"
Wall Section(s) @ 3/4" = 1'-0"
Other Sections & Details @ 3/4" = 1'-0"
Note: Include at least four (4) feet of the existing house on both the floor plans and
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elevations. Identify each existing room by name, locate existing door and window openings,
and indicate any changes needed to the existing house and house wall as a result of the
proposed addition.
The plans for an addition or an aggregation of additions must be professionally sealed by a
Missouri Licensed Architect or Professional Engineer where the total floor area exceeds 50
% of the existing total floor area or where the total area of the addition(s) exceeds 1000
square feet. The total floor areas shall include all finished space. All plans required to be
sealed by this criteria, shall be dated and bear an original embossed or inked seal and
original signature of the Missouri Registered Architect or Engineer on the cover sheet of
each set of plans (four sets required) submitted to this office. All other sheets within the
sets of plans must also be sealed with an original seal or a mechanically reproduced seal.
The plans shall include the name, address, and phone number of the Architect or
Engineer.
Include one of the following in your plan submittal depending on choice of floor and/or roof
framing systems:
(1)
If by conventional method, indicate size and spacing of floor joists, rafters, ceiling
joists, and/or ties on the sections and details included in the plans submitted.
(2)
If by the "truss" method, submit four (4) copies of the engineer's sealed truss plan
which can be obtained from the lumber dealer or the "truss" fabricator. Trusses to
comply with AFPA NDS-05 and TPI 1-2002.
5.
If a pre-fab fireplace or wood burning stove is to be installed include a section drawing at
3/4" = 1'-0" scale in your plan submittal and also provide one (1) copy of the manufacturer’s
installation instructions. (The unit shall be certified or tested by a nationally recognized and
approved testing agency and bear that agency's label.)
6.
If the finished area of the addition exceeds 25% of the finished area of the existing house
the following must be provided with your submittal:
Four (4) copies of the heating and air conditioning plans for the addition (separate
system) or for entire house including proposed addition (combined system).
Two (2) copies of heat loss/heat gain calculations for the addition (separate system)
or for the entire house including proposed addition (combined system).
7.
When the existing house is served by a septic or other on-site sewage disposal system,
new bedroom additions, or any habitable room addition which could be converted to use as
a bedroom, requires that the adequacy of the septic system to handle the additional
potential load, be verified by the Plumbing Inspection Section. Refer to separate handouts
regarding rules, regulations and procedures for septic systems.
8.
All plumbing and electrical work must be performed in accordance with St. Louis County
Codes and Ordinances by licensed master plumbers, licensed electrical contractors, or a
pre-authorized homeowner who by examination has demonstrated the knowledge and
ability to perform the work. All mechanical work must be performed by a licensed
Mechanical Contractor (bonded and insured) authorized to do mechanical work.
Homeowners may perform their own mechanical work within their own dwelling with no
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requirement to be registered or licensed.
9.
It is the applicants’ responsibility to check with other agencies or jurisdictions concerning
their requirements that may be affected by the proposed addition. Contact the appropriate
agencies such as the Highway Department, Fire Department, Municipality, Sewer District,
Subdivision Trustees, etc.
10.
Issuance of a building permit for the project does not authorize construction access to the
work site. If the existing driveway entrance to the site is unavailable for construction
access, the owner/contractor shall apply for a permit to construct a temporary entrance
from the owner of the Right-of-Way.
For additional information regarding the criteria in this handout, please contact:
Contact
(314) 615-5184
(314) 615-7155
(314) 615-3763
(314) 615-5485
General Information
Permit Processing
Zoning Review
Building Plan Review
Right-of-Way Owner
State
County
Municipality
(888) 275-6636
(314) 615-8517
Municipality
Refer to the attached drawings and the following listing of common code requirements pertaining
to most simple residential room additions:
FOOTINGS
BEARING ON UNDISTURBED SOIL
2000psf BEARING CERTIFIED BY A MISSOURI
1
PROFESSIONAL ENGINEER
Framed Wall
Framed Wall
w/Brick Veneer
Framed
Wall
Framed Wall w/Brick
Veneer
1 Story slab on Grade
12”
12”
12”
12”
1 Story w/Basement
21”
24”
16”
18”
2 Story slab on Grade
15”
21”
12”
16”
2 Story w/Basement
24”
30”
18”
23”
3 Story Slab on Grade
23”
32”
17”
24”
3 Story w/Basement
27”
36”
21”
27”
1. Documented by a letter/statement sealed by a Missouri Professional Engineer.
The foundation wall shall set in the middle of the footing. The footing thickness shall be a
minimum of 6 inches but not less than the distance the footing extends horizontally past the
face of the foundation wall.
The bottom of all footings must be a minimum of 2'-6" below finished grade and bear on
undisturbed soil or prepared fill.
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FOUNDATION WALLS
Minimum 8" thick keyed to footing and extending minimum 8" above finished grade.
1/2" round anchor bolt, placed a maximum of 6'-0" o.c. and at corners or ends, set a minimum of
7" into concrete required for anchoring of sill plates (2x4 minimum) around entire foundation with
1½” washers and nuts for a room addition serving a one and two family dwelling.
Exception: Use 2”x2”x3/16”square washers in lieu of 1 ½” round washers for anchor bolts
securing a portal panel.
One should use 3”x3”x0.229” square washers for a room addition serving a townhouse (3 or more
attached dwellings). All sill plates shall be grouted level or have sill sealer with approved shim
materials and methods.
CONCRETE
Minimum thickness of concrete floor slabs supported directly on the ground is 3-1/2". The slab
shall be placed over a minimum 4" base course of gravel or crushed stone and a 6 mil.
polyethylene film vapor barrier.
Exception: The 4” base course of gravel or crushed stone is not required when the base of
the slab is above the outside grade.
Minimum compressive strength of concrete shall be:
2500 psi - floor slabs
3000 psi - foundation walls and footings
3500 psi - porches, walks, patios and steps
Concrete for all foundation walls, porches, walks, patios and steps shall be air-entrained.
STRUCTURAL FRAMING
Indicate size, weight and spacing of all steel beams and columns. Indicate size, fiber stress, type
and grade of lumber of all wood beams and columns. Identify interior bearing wall locations.
Indicate direction of floor joists, size, spacing, fiber stress, type and grade of lumber shown.
Exterior wall framing to be constructed in accordance with the following Table. The grade of studs
shall be standard grade or better.
STUD SIZE
(inches)
2x4
2x6
a
Laterally
unsupported
stud height (feet)
10
10
Maximum
spacing when
supporting roof
and ceiling only
(inches)
a
24
24
Maximum
spacing when
supporting one
floor, and roof
and ceiling
(inches)
a
16
24
Maximum
spacing when
supporting two
floors, roof and
ceiling (inches)
--16
Maximum
spacing when
supporting one
floor only
(inches)
24
24
Roof structure spans a maximum of 32’
WALL BRACING FOR LATERAL WIND FORCES
Alternative Foundation Systems
In the case of a room addition that does not have its exterior walls prescriptively connected to a
continuous perimeter footing and foundation (such as an addition built on a post and pier system),
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four sets of structural details and one set of structural calculations (all properly signed, sealed and
dated by a Missouri Registered Design Professional) must be submitted to address how the lateral
wind loads from the room addition are transferred to and resisted by the foundation elements.
New Walls Of The Room Addition
New walls of the room addition shall be braced against lateral wind loads in compliance with:
a. the attached “Room Addition Bracing Guideline for One and Two Family Dwellings”; or
b. Section R602.10 of the 2009 International Residential Code (a compilation of the major
points of this is contained in the Appendix A1 Wind and Seismic Bracing Guideline For One
and Two Family Dwellings and Townhouses found under the “Guides” link at:
www.stlouisco.com/pubworks); or
c. accepted engineering practice, which must be demonstrated with four sets of structural
details and one set of structural calculations (all properly signed, sealed and dated by a
Missouri Registered Design Professional) in accordance with the 2009 International
Building Code and its referenced standards.
Existing Wall Opening Alterations With The Construction Of An Adjacent Addition
As part of the construction of a room addition adjacent to an existing building, any existing
openings in the existing building that are not having their opening widths increased may have their
heights altered (e.g. window openings may be changed into door openings with the removal of the
knee walls). Additionally, the following opening alterations will also be accepted in the existing
exterior walls of the existing building without requiring a structural justification of the altered wall’s
ability to resist lateral wind loading:
a. a single new opening, or an accumulative width of multiple new openings, totaling 6’ or less
in width may be created in any of the braced wall lines (see below) of the existing building;
or
b. a single new opening, or an accumulative width of multiple new openings, exceeding 6’ but
less than or equal to 20’ in width may be created, if the opening(s) width is less than 50%
of the applicable braced wall line (see below).
A braced wall line is typically a straight wall but could include some offsets. A single offset of 4
feet or less or multiple offsets of 4 feet or less each (as long as the sum of all the offsets is 8 feet
or less) may all be part of single braced wall line. (See Figure1)
Opening alterations other than those described above require the submittal to demonstrate the
altered existing braced wall line is adequate to resist the lateral wind loads in the same manner as
is required for new walls in the New Walls Of The Room Addition section above. If accepted
engineering practice is the method chosen, the Missouri Registered Design Professional may
substitute a properly signed, sealed, and dated structural certification to accompany the structural
plans in lieu of the usual structural calculations. Such a certification must unequivocally state that
the affected existing wall lines, with the proposed modifications shown on the plans, will comply
with the lateral bracing provisions of Section R602.10 of the 2009 edition of the International
Residential Code OR Section 2305 of the 2009 edition of the International Building Code.
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Existing Stories With Vertical Additions Constructed Above Them
Vertical Additions are largely beyond the intended scope of this guide for simple additions, but
when an addition is constructed on top of an existing story of frame or partial frame construction
(as opposed to full masonry or concrete construction), the submittal must demonstrate that
existing story is adequate to resist the increased lateral wind loads in one of the manners required
for new walls in the New Walls Of The Room Addition section above. If accepted engineering
practice is the method chosen, the Missouri Registered Design Professional may substitute a
properly signed, sealed, and dated structural certification to accompany the structural plans in lieu
of the usual structural calculations. Such a certification must unequivocally state that the existing
stories, with the proposed addition associated modifications shown on the plans, comply with the
lateral bracing provisions of Section R602.10 of the 2009 edition of the International Residential
Code OR Section 2305 of the 2009 edition of the International Building Code.
Vertical additions will typically also require other structural issues beyond wall bracing to be
addressed, such as the adequacy of existing footings, foundations, headers and/or other framing.
Addressing these issues typically must be in the form of properly signed, sealed, and dated
structural plans as well as either calculations or a structural certification from a Missouri
Registered Design Professional.
Figure 1
ROOF FRAMING
For conventional framed roof systems, indicate size, spacing, fiber stress, type and grade of wood
for roof rafters and ceiling joists. Indicate roof pitch. Show rafter and ceiling joist framing layout on
plans.
Trussed roofs and/or floors shall have sealed truss plans indicating spacing and roof pitch for
each span utilized. Include girder trusses if utilized. Show truss framing layout including girder
locations on the plans. All trusses shall comply with TPI 1-2002.
All roof framing shall be designed to support the following minimums:
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Top chord of trusses
or roof rafter:
Ceiling joists or
Bottom chord of trusses:
Snow Load 20 lb. per sq. ft.
Dead Load Use actual dead load.(Note: Dead load must include
2 layers of roofing membrane
Use a live load of 20 lb. per sq. ft when there is a possibility of
attic storage. Attic storage shall be addressed where a 42” high, 24”
wide rectangle can be placed perpendicular to the rafter/ceiling joists
or trusses. Use 10 lb per sq. ft. live load where there is no attic
storage. Dead load—use actual dead load.
Note: The live load design on the ceiling joist or bottom chord of a truss shall not be required
if all of the following conditions are adhered to:
a. Attics with drywall ceilings below that are accessed only by a 22" x 30" scuttle
opening without a pull-down stairway.
b. Warning signs attached to the trusses on each side of the scuttle opening at
least 36" above the bottom chord and within 18" of the edge of the opening. The
signs shall be constructed of metal or other approved durable materials suitable
for the location and be a minimum of 40 sq. inches in area with 3/4" minimum
high letters on a contrasting background that reads “WARNING-TRUSSES NOT
DESIGNED FOR ATTIC STORAGE”.
c. Attic areas over garage areas with drywall ceilings shall also be provided with a
horizontal railing attached to the trusses on each side of the scuttle opening at
least 24" and not more than 36" above the bottom chord. The railing is intended
to be an obstruction to easy access for storage and shall be constructed of either
1x4's, 2x4's or 3/8"x 6" plywood. It may be shop or field applied.
Where trusses or rafters are spaced 24" o.c., roof panels shall be a minimum of 15/32” thick
sheathing without edge support or a minimum of 3/8" thick (minimum 24/0 span rated)
sheathing with edge support. Edge support shall be tongue-and-groove edges, panel edge
clips (at mid-point between each support) or 2x lumber blocking.
ROOFING
Class A, B, or C roofing shall be required where the edge of the roof is less than 3’ to the
property line.
Underlayment for asphalt shingles:
Slopes of 2:12 to less than 4:12 shall be protected with two layers of underlayment.
Apply a 19” strip of underlayment felt parallel with and starting at the eaves, fastened
sufficiently to hold into place. Starting at the eave, apply 36” wide sheets of
underlayment. Successive 36” wide sheets of underlayment shall overlap the previous
36” wide sheet by 19”. All underlayment shall be fastened sufficiently to hold into place.
Slopes equaling or exceeding 4:12 shall be protected with one layer of underlayment.
Underlayment shall be applied shingle fashion, parallel to and starting from the eave
and lapped 2”, fastened sufficiently to hold in place. End laps shall be offset by 6’. All
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underlayment to be a minimum of Type I per ASTM D226-06 or Type I per ASTM
D4869-05e01(Type I is commonly called No. 15 asphalt felt.)
Indicate corrosion-resistant flashing at all wall and roof intersections, changes in roof slope or
direction, around all roof openings, intersections with chimneys, intersection of exterior walls
and porches and decks, etc. Valley flashing shall be installed per R905.2.8.2
Built-up membrane roof slope is 1/4:12 with approved low-slope roof covering materials. A
Coal-Tar built-up membrane may be installed on 1/8:12 slope.
Mineral-surfaced roll roofing shall conform to ASTM D 224, D 249, D 371, D 3909. It shall not
be installed on roof slopes below 1:12.
SMOKE DETECTORS AND CARBON MONOXIDE DETECTORS
AC powered, U.L. listed smoke detectors with battery backup shall be placed throughout the
dwelling unit as noted below unless already existing. All detectors within the dwelling shall be
interconnected and hard wired so that the activation of any alarm will sound all alarms throughout
the house.
Exception: Detector locations in existing areas shall not be required to be interconnected
and hard wired where the alterations or repairs do not result in the removal of interior wall
or ceiling finishes exposing the structure, unless there is an attic, crawl space, or basement
available which could provide access for hard wiring and interconnection without the
removal of interior finishes.
Smoke detectors shall be placed in the following locations:
Floor levels with bedrooms: A smoke detector is required in each bedroom and one
centrally located detector is required outside of a group of bedrooms in the hall way.
Floor level without bedrooms: A smoke detector is required adjacent to the stair.
A Carbon Monoxide alarm complying with UL2034-2008 shall be installed outside of each
separate sleeping area in the immediate vicinity of the bedrooms in dwelling units within which
fuel-fired appliances are installed and in dwelling units that have attached or basement garages.
WALLS
Approved water resistant gypsum backer board is required in bathtub and shower compartments.
Interior finish materials shall not have a flame spread rating exceeding 200.
Brick veneer and masonry walls require corrosion-resistant corrugated sheet metal wall ties
minimum 22 ga. by 7/8" wide at 24" o.c. vertically and 24" o.c. horizontally (maximum) and shall
support no more than 2.67 square feet of wall area (2 square feet maximum on an addition
serving a townhouse). 1" minimum air space between brick and sheathing required. Brick veneer
anchors around openings larger than 16” in either direction shall be spaced a maximum 3’-0” o.c.
maximum around the perimeter of and within 12” of the opening. Brick veneer walls require
weepholes at least 3/16" dia. spaced less than 33" apart.
Weather- resistant sheathing paper (Asphalt saturated felt 14# per square otherwise known as
Type I felt, Tyvek, Typar, or other approved weather resistant material) shall be installed under
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all siding and brick/stone veneer listed in Table R703.4
INSULATION
Indicate type, thickness and "R" values of all insulating materials.
Foam plastic insulation shall be separated from the interior of the building by 1/2" gypsum
wallboard.
FIRE BLOCKING
Top and bottom of all conventional, double stud, furred spaces, and staggered stud frame
walls are to be fireblocked vertically at the ceiling and floor levels and horizontally at intervals
not exceeding 10’.
Fireblocking required at all soffits and dropped ceilings.
Fireblocking required between stairway stringers at the top and bottom of the run. Enclosed
accessible spaces under stairs shall have walls, under stair surface and any soffits protected
on the enclosed side with ½ “ gypsum board.
Fireblocking required around vent, pipe, and duct penetrations of ceilings and floors.
Fireblocking required at the dwelling unit separation line of the cornices of two family dwellings
and townhouses.
All spaces between the chimney and the floors and ceilings the chimney passes through shall
be fireblocked (1’’ depth of batt or blanket of mineral wool or glass fiber supported by strips of
metal or metal lath).
ATTIC AND CRAWL SPACE ACCESS
A 22" x 30" minimum access opening required for attic areas which have a clear height of over 30".
A 16" x 24" minimum access opening is required for crawl spaces.
LIGHT AND VENTILATION
Glass area in habitable rooms shall not be less than 8% of floor area served. One-half of this area
must be available for unobstructed ventilation with screens included.
All bedrooms and basements with a partial or complete finish must have one window for
emergency escape meeting the following minimums:
Maximum height to clear opening: 44"
Minimum clear height: 24"
Minimum clear width: 20"
Minimum clear opening area: 5.7 sq.ft.
Exception: Windows less than 44” above the exterior ground may have a minimum
net clear opening of 5.0 sq.ft. The emergency escape window shall be operable from
the inside without the use of special knowledge, tool or extra force, beyond that
required for normal window operation.
Compliance with the above must be indicated by one of the following methods: (Simply showing
the rough frame opening for windows is specifically not acceptable.)
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1.
A window schedule showing net window opening, net glass area and window type
and keyed to specific location in the normal manner, or
2.
Net opening, net glass area and window type may be shown at each location on the
plans, or
3.
A specific manufacturer and its sizing Code Number may be indicated at each
location on the plans.
Indicate clear opening height above the floor level and size of all windows on elevation drawings.
Attic and enclosed rafter space ventilation (net free) area is to be at least 1/150 of the area
served. Two remote vents required for each Attic/space (minimum).
Exception: Required ventilation area may be reduced to 1/300 where a vapor retarder
having a transmission rate not exceeding 1 perm is provided on the conditioned side of
the insulation, or if the gable or ridge vents are located in the upper 1/3 of the attic or
enclosed rafter space and provide 50% to 80% of the required vent area with the
balance of the required vent area is supplied by eave or cornice vents. A 1’’ clearance
between the top of the insulation and the bottom of the roof sheathing is required when
ventilation is provided by eave or cornice vents.
Foundation crawl spaces are to have a minimum clear height of at least 18" and shall be
provided with vent openings located within 3’ of each corner. The total vent area shall be at
least 1/150 of the area served.
Exceptions:
1. When an approved vapor barrier is provided over the surface of the ground the
required vent area may be reduced to 10% of the above and the vents may have
operable louvers.
2. Clear height may be reduced when preservative-treated or naturally durable wood is
used for the framing and subfloor.
Enclosed attic, rafter and crawl space areas may be ventilated by a mechanical exhaust and
supply air system of .02 cfm/sq. ft. of horizontal area. The ventilation systems shall operate
continuously. The floor of the crawl space shall be covered with a Class I vapor retarder. The
exterior walls of the crawl space shall be insulated to R-5. See the Insulation Section of this
document for restrictions on exposed insulation.
Unfinished basements and utility rooms require natural ventilation (net openable area) at the ratio
of 1% of the square footage floor area served. Mechanical ventilation with outdoor air (not
recirculated air) in accordance with the mechanical code may be substituted at a rate of .05 cfm/sq.
ft. of area.
SAFETY GLAZING:
Glazing installed in the following locations shall be tested and labeled in accordance with
CPSC 16 CFR Part 1201 Standard as a Type I or II category (glazing in sliding doors; any
glazing exceeding 9 square feet in area required to be safety glazing in accordance with one of
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the six categories listed below; and all glazing in doors and enclosures for hot tubs, whirlpools,
saunas, steam rooms, bathtubs, and showers shall be a Type II category and noted as such
on the Architectural plans):
As an option, one may use glazing tested in accordance with ANSI Z97.1 in hazardous
locations other than in enclosures for hot tubs, whirlpools, saunas, steam rooms. bathtubs, and
showers. Type B glazing may be used in lieu of Type A for panes 9 square feet or less in area.
Type A is required for all sliding glass doors and glazing exceeding 9 square feet in a
hazardous location.
Indicate size of all windows, bottom edge of window height above the floor, and the horizontal
distance from the edge of a window to a door where safety glazing might be required by the
following conditions. Glazing in the following locations shall be safety glazing:
1. Glazing in doors and any portion of a building wall or fence enclosing bathtubs, showers, hot
tubs, whirlpools, saunas, steam rooms, spas, indoor or outdoor pools which is located 60” or
less, measured horizontally, from the water’s edge and less than 60" vertically above a
standing surface.
2. Any glazing material adjacent to a door if the nearest vertical edge of the glazing material is
within a 24" arc of either vertical edge of the door in a closed position and if the bottom edge
of the glazing material is less than 60" above the floor.
Exceptions:
a. Where there is an intervening wall or barrier to prevent a person from striking the
glazing while approaching the door.
b. Glazing adjacent to a door serving a closet or storage area 3’ or less in depth
c. Decorative glass
d. Glazing in walls on the latch side of and perpendicular to the plane of the door in
a closed position.
e. Glazing that is adjacent to the fixed panel of the patio doors.
3. Safety glazing is required for fixed or operable panels that meet all of the following:
a.)
individual pane greater than 9 sq. ft. and;
b.)
bottom edge less than 18" above floor and;
c.)
top edge more than 36" above floor and;
d.)
walking surface within 36" horizontally
Exceptions:
i. Decorative glass.
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ii. 1 ½” protective bar is placed 34’’ to 38’’ above the walking surface. The bar
shall be capable of withstanding a 50 pounds per linear foot load without
contacting the glass.
4. All doors
Exception: Decorative glass
5. Glazing in hand or guard rails
6. Glazing adjacent to stairways, landings, and ramps within 36’’ horizontally of the walking
surface and less than 60’’ vertically above the plane of the walking surface.
And
Glazing adjacent to stairways within 60’’ horizontally of the bottom tread in any direction
when the exposed surface of the glass is less than 60’’ above the tread nosing.
Exception: The glazing is protected by a guardrail or a handrail, including
balusters or in-fill panels complying with the provisions of Sections R301.5 and
R312 and the glazing is located more than 18’’ horizontally from this guard or
handrail.
The following products and uses are specifically exempt from the standard for architectural
glazing in hazardous locations:
1.
Louvered windows and jalousies 3/16’’or greater in thickness and no longer than 48’’.
2.
Openings in doors through which a 3 inch diameter sphere is unable to pass.
ENERGY CONSERVATION
Typical sections through the building must be provided indicating the type, thickness and "R" value
of insulating materials. "U" values of the windows, doors and skylights must be specified.
Design requirements by Accepted Practice Method: (R-values indicated must be obtained by the
insulation material used, not by the total system).
Roof/Ceiling
Min. R-30
Frame wall & band joists
Min. R-13
Floor over unheated crawl space
Min R-19
Finished Basement Walls
Min. R-13 (full height)
Unfinished Basement Walls
Min. R-5
Exception: Unfinished basements may have up to a maximum of 20% of the total
basement wall area exposed above the outside finished grade/ground level as uninsulated concrete foundation walls. The foundation wall area above the outside
grade/ground level that may be un-insulated is determined by the formula .20 times
the basement wall height of all walls (including insulated exterior frame walls for
walk-out basements and walls common to both basement and attached garages)
times the perimeter of these basement walls. In unfinished areas the basement
foundation wall insulation shall extend down to the basement floor slab or to a
minimum of 24 inches below outside finished grade when the grade is above the
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floor slab elevation.
Slab-on-grade floors:
Min. R10 when there is no ductwork in the slab
Min. R15 when there is ductwork in the slab
The insulation shall be along the perimeter of the foundation wall downward from
the slab a minimum distance of 24" or horizontally under the slab for a minimum of
24".
Windows and doors
Max. U-Factor of 0.40
Mechanical supply Ducts outside the building thermal envelope shall be insulated to a
minimum of R-4
An energy calculation verifying overall envelope compliance shall be provided if any one of the
exterior envelope components listed above is not met.
DOORS
Locks with thumb turns on the inside are permitted. Inside key operation is permitted provided the
key cannot be removed from the lock when locked from the inside.
Minimum width of an interior egress door leaf is 28" (2'-4" door leaf).
EXTERIOR STAIRS & STAIR/PORCH LANDINGS
All doors require a 3’x 3’ landing a maximum of 1.5” below the door threshold. The landing is
typically the deck or porch surface.
Exceptions:
1. A landing serving the primary means of egress (main entry door) of the house shall be a
maximum of 7 ¾” below the door threshold as long as the door, other than the exterior
storm or screen door, does not swing outward over the landing.
2. A landing serving a door not considered a primary means of egress (i.e. kitchen door
leading to a deck) may be placed at the bottom of a stair consisting of four risers or less
(8 ¼” maximum per rise) as long as the door, other than the exterior storm or screen
door, does not swing outward over the stair.
Minimum clear width of stairways is 36".
Minimum headroom clear height of stairways is 6'-8" measured vertically
Note number and size of stringers (2 x 12's minimum) and material used for treads. Stairs
shall be designed for a 40 psf live load or 300 lb. concentrated load on 4 sq. inches at mid
span of a tread; whichever produces the greater stress and deflections.
Maximum riser height is 8 ¼" and the minimum tread depth (measured horizontally from tread
nose to tread nose) is 9". A ¾’’ tread nosing is required on stairways with solid risers.
Exception: Nosing is not required where the tread depth is 11’’
Stair winders must have 9" minimum tread depth at a point not more than 12" from the narrow
end and be at least 6" in depth at the narrow end.
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Indicate at least one continuous handrail on stair plan and section at 34’’ to 38" above nosing
for stairs with 4 or more risers. The handrail ends shall return to the wall or newel post.
Handrails (and other projections below the handrail) shall not project more than 4 1/2" into the
required stairway width.
Handrails (and other projections below the handrail) shall not project more than 4 1/2" into the
required stairway width.
Guards along open-sided stairs with a total rise more than 30’’ shall be a minimum of 34’’in
height above the leading edge of the tread and minimum of 36" in height at the stair landings.
Minimum 36" high guards shall be provided along balconies, areaways, mezzanines and opensided walking surfaces where the difference in floor levels is more than 30’’
Open guards shall have intermediate vertical balusters spaced less than 4" apart.
Exception: Openings on the side(s) of a stair shall have balusters spaced less than
4 3/8” apart.
DECKS
For larger exterior decks obtain St. Louis County "Building Permit Requirements For Sun-Decks"
for additional information and details that need to be included on the plans.
PRE-FAB FIREPLACES
Combustible trim and mantels attached to the fireplace face shall be a minimum of 6" from the
opening. Combustible material within 12” of the fireplace opening shall not project more than 1/8”
for each 1” distance from the opening.
Hearth sizes:
Solid fuel with 6 sq.ft. of opening or more = 1'-8" minimum, and 12" each side.
Solid fuel with less than 6 sq.ft. of opening = 1'-4" minimum, and 8" each side.
Gas fired - per manufacturer's installation instructions.
Chimneys shall extend above the roof that they penetrate a minimum of 3'. Chimney outlets shall
be 2' higher than any portion of the building within 10' horizontally.
Indicate chimney locations on the exterior elevations.
All pre-fab metal fireplaces and stoves indicate manufacturer, make and model number directly on
the plan. Provide 1 copy of manufacturer's installation instructions and proof of testing by a
nationally recognized testing agency.
Gas fireplaces, gas logs, and gas room heaters shall be installed in accordance with Chapter
24. Combustion air shall be provided in accordance with Section G2407.
Factory-built or masonry fireplaces shall be equipped with an exterior air supply to assure
proper fuel combustion. The air duct serving the exterior air intake and the interior air outlet
shall be listed and installed in accordance with the manufacturer’s installation instructions for
both the factory-built and the masonry fireplace. The cross sectional area of the passageway
shall be a minimum of 6 square inches but not more than 55 square inches unless otherwise
noted in the installation instructions. The exterior air intake (covered with a corrosion resistant
screen of ¼’’ mesh) may draw air from a naturally ventilated crawl space or attic. The interior
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air outlet may be located in the back or sides of the fireplace chamber or within 24 inches of
the firebox opening on or near the floor. The interior air outlet shall be closable and designed
to prevent burning material from dropping into a concealed combustible space. Exterior air
intakes shall be installed below the level of the base of the firebox when the interior air inlet is
installed inside the fireplace chamber.
MINIMUM ROOM DIMENSIONS
Habitable spaces, hallways, corridors, bathrooms, toilet rooms, laundry rooms and portions of
basements containing these spaces, shall have a minimum clear height of 7'-0". All habitable
rooms, except kitchens, shall have an area of not less than 70 square feet and shall not be less
than 7’-0” in any dimension.
HEATING AND AIR CONDITIONING AND GENERAL MECHANICAL
For additions less than 25% of the size of the existing finished area of the house show how the
addition will be heated on the floor plan. Indicate duct extensions and diffuser locations (if
extending existing system), baseboard units, or other acceptable method of providing
heating/cooling.
Bathrooms and water closet compartments shall be provided with an aggregate
glazing area in windows of not less than 3 square feet with 1.5 square feet of
openable area.
Exception: An operable window shall not be required if artificial light
is provided and a 50 cfm exhaust fan (vented to the exterior) is
provided. It is permissible to discharge the exhaust to an attic gable
vent.
ELECTRICAL
Show location of all receptacles, lights, ceiling fans, exhaust fans and switches on the floor plan.
Identify all 240 volt receptacles/circuits. Indicate which light and/or receptacles are controlled by
switches.
Ground fault circuit-interruption protection shall be provided for all 125 volt, single
phase, 15 and 20 ampere receptacles installed in the following locations:
1. Bathrooms
2. Garages except ceiling mounted receptacle for garage door opener
3. Outdoors (including inside screened enclosures)
4. Unfinished basement areas and crawl spaces except for laundry circuit and
single receptacle dedicated to sump pumps.
5. Receptacles intended to serve kitchen counter top surfaces.
6. Receptacles intended to serve the counter top surfaces of a wet bar that are
located within 6'-0" of the outside edge of the wet bar sink.
Arc-fault circuit interruption protection shall be provided for all circuits supplying power
to bedrooms.
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Receptacles are required to be installed in the following areas:
1. In all habitable rooms except bathrooms so that no space along a wall is more
than 6'-0"from a receptacle. All wall spaces 2'-0" wide or greater require
receptacles. Fixed panels of glass doors, fixed room dividers such as free
standing bar-type counters or railings shall be included in the 6'-0"
measurement.
2. In hallways of 10'-0" or more in length. (Foyer is an entry hallway.)
3. Kitchen and dining area counter top receptacles shall be supplied by at least 2
different 20 amp circuits. Receptacles shall be installed so that no point along
the counter is more than 24" from a receptacle. All counter top areas 12" wide
or greater separated by sinks, ranges or refrigerators shall be provided with
receptacles. Receptacles installed face-up in counter work-surface are
prohibited. At least one receptacle shall be installed to serve each island or
peninsula counter space that is 24" x 12" or greater.
4. In bathrooms at least one wall mounted receptacle installed within 36" of each
basin.
5. Outdoor receptacles (weather-proof type) installed at the front and back of the
house, accessible to grade level and not more than 6'-6" above grade level.
6. At least 1 receptacle in laundry area supplied by a dedicated 20 ampere
branch circuit.
7. At least 1 receptacle in unfinished basement areas and the garage in addition
to the laundry receptacle.
8. Required receptacle outlets located in floors shall be within 18" of wall or fixed
room divider and shall be installed in boxes listed for the purpose.
9. An exterior receptacle is required to serve a balcony, deck, and porch. This
outlet shall be a maximum 6’-6” above the deck floor.
Lighting is required in the following areas:
1. At least 1 wall switched lighting outlet shall be installed in every habitable
room, bathroom, hallway, stairway, attached garage, detached garage (with
electrical power) and at exterior doors. Occupancy sensors may be used in
addition to a wall switch or be equipped with a manual override and be located
at the customary wall switch location.
2. At least 1 lighting outlet and one receptacle are required in each attic, crawl
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space, basement or utility room that is used for storage or contains heating,
air-conditioning or other equipment requiring servicing. The light switch shall be
located at the point of entry.
Lighting in clothes closets:
1. The use of incandescent fixtures with open or only partially enclosed lamps and
the use of pendant fixtures are prohibited.
2. Fixtures may be located only where there are the following minimum
clearances to the nearest point of storage space:
- surface mounted incandescent fixtures - 12" minimum.
- surface mounted fluorescent fixtures and recessed fixtures - 6" minimum.
Electrical panels:
1. Electrical panels shall not be installed in bathrooms or clothes closets.
2. Lighting is required in the vicinity of the electrical panel.
3. Electrical panels in new construction shall not be installed in areas with less
than 6'-6" headroom.
4. A minimum clearance of 3’-0” deep and 30” wide is required in front of
electrical panels. Counters and cabinets cannot be installed under the electrical
panel.
Lighting fixtures above bathtubs:
No parts of hanging fixtures, track lighting and ceiling paddle fans shall be installed
within 3'-0" horizontally of a bathtub, measured from the outside edge of the tub and 8'0" vertically from the top of the tub rim.
PLUMBING
When applicable, show location of bar sink, lavatories, water closets, bathtubs, showers,
hose bibs and other plumbing fixtures on the plans. Show location of plumbing chases.
Show location of washer hose connection bibs and laundry standpipe for washer/dryer
area.
Gutters and downspouts required on roof overhangs less than 36"
Note:
The preceding requirements apply to most simple residential room additions.
However, the Plan Reviewer may determine that unusual circumstances dictate the need
for additional information on any particular project.
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ROOM ADDITION BRACING GUIDELINE FOR ONE AND TWO FAMILY DWELLINGS
OR TOWNHOUSES
The construction documents shall detail the locations and widths of all braced wall panels
in accordance with the following criteria:
1. The building exterior walls shall be sheathed with 7/16 inch or thicker plywood or
OSB wood structural panels. The wood structural panels shall be applied to all
exterior walls, gable ends, and band boards. All vertical joints between panels
shall be blocked. Horizontal joints in braced wall panels shall be blocked.
2. Braced wall panels shall be located in every exterior braced wall line in
accordance with the following criteria:
a. The outside edge of the first braced wall panel meeting the width established
in Table R602.10.10.3 shall be a maximum of 12.5 feet or less from each end
of the braced wall line. The outside stud of the first braced wall panels closest
to the ends of the braced wall line shall be secured with a hold-down device
securing the end stud to the foundation with a minimum uplift design value of
800 pounds.
Exception: The 800 pound hold-down device is not required when the
braced wall panel is placed at the end of the braced wall line and there is
a 24 inch wide full height sheathed wall placed 90 degrees to the end of
the braced wall line and panel.
b. The centerline spacing of braced wall panels in a braced wall line may not
exceed 25 feet.
3. Braced wall panel locations shall be shown on the floor plans or the elevation
views and meet the widths established in Table R602.10.10.3.
TABLE 602.10.10.3
SIMPLIFIED BRACING PANEL WIDTHS
8’ wall height
32”
16” d
WIDTH OF SOLID PANEL a, b
9’ wall height
10’ wall height
36”
40”
18” d
20” d
12’ wall height
Plywood/OSB Panel
3:1
48”
Simplified Portal Wallc
6:1
24” d
a. Linear interpolation is permitted
b. Wall height is the vertical distance from the bottom of the sole/sill plate to the top of the double top plate. An additional 2 inch (50.8
mm) variation in height is allowed for pre-cut stud framing.
c. The Simplified Portal Wall, if applicable, shall be constructed in accordance with the applicable detail in Figure R602.10.10.3. The
designer shall provide this detail on the construction documents.
d. The Simplified Portal Wall width assumes the beam is placed under the top plate of the wall. A smaller width may be calculated for a
lower top of beam height using the 6:1 height to width ratio.
4. The exterior wall corners shall be constructed in accordance with the applicable
detail in Figure R602.10.10.4.
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Exception: Braced wall panels located in accordance with Item 2.
5. When the perpendicular distance between the exterior braced wall lines exceeds
50 feet, the registered design professional shall include the following certification
on the drawings:
The interior and exterior wall configuration braces the structure in accordance
with or equivalent to the lateral bracing provisions of Section R602.10 of the
International Residential Code, 2009 edition or Section 2305 of the International
Building Code, 2009 edition.
6. Wall height may not exceed 12 feet (12’-2” actual maximum height). Walls
greater than 12 feet in height shall be designed and detailed by the registered
design professional to resist wind loads in both the longitudinal (racking and
parallel) and transverse (perpendicular) directions.
Exception: Structural calculations and details are not required in the following
situations:
a. Longitudinal structural calculations are not required when there are no
braced wall panels in that portion of a wall where the height exceeds
12 feet and that greater wall height segment is part of a prescriptive
braced wall line on each of the adjacent stories.
b. Transverse structural calculations are not required if the wall
exceeding 12’-2” complies with Table R602.3.1 of the 2009
International Residential Code (IRC).
7. Braced wall panel connections to floor and roof/ceiling assemblies shall comply
with Sections R602.10.6 and R602.10.7 of the 2009 International Residential
Code (IRC).
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