Tub and Shower Installations

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Tub and Shower Installations
                         CITY OF NEWARK, CALIFORNIA                                                   BUILDING INSPECTION DIVISION
                         37101 Newark Boulevard, Newark, CA 94560-3796 • 510-578-4261 • Fax 510-578-4307 • e-mail: building.inspection@newark.org

GENERAL
Building permits must be obtained prior to installing or making major repairs to bathtubs, shower stalls,
and tub/shower combinations. Permits can be obtained at the Building Inspection counter located at
City Hall. The Building and Plumbing Codes set forth minimum standards for the installation of tub and
showers. The most common of those standards are included below.

PEST CONTROL REPORTS
Often, repairs to existing showers are a result of a pest control investigation. If a pest control report was
written for this work, provide two copies to the Building Inspection Division when applying for a
permit.

TUB ONLY INSTALLATIONS
The installation or replacement of a bathtub without a shower needs a single plumbing inspection only.
Enclosures, waterpoof wall surfaces, shower curtains and doors are not required by code provided the
bathtub does not have the ability to be converted to a shower.

GENERAL SHOWER ENCLOSURE STANDARDS
There are a number of size, configuration, and construction standards for showers which are listed
below:
• Minimum interior dimension = 30"
• Minimum interior area = 1,024 square inches
• Waterproof wall finishes must extend a minimum 70" above shower drain.
• Shower heads must discharge below the top edge of waterproof wall finish.
• Control valves must be of the pressure balance or thermostatic mixing valve types.
• Hinged shower doors must swing outward.
(See Figures B and C for additional detail.)

TUB/SHOWER STALL WINDOWS
The glazing in all windows located within a tub or shower enclosure and having a sill which is less than
60 inches above the drain shall be tempered glass. Sills shall be sloped to drain back into the shower
stall as shown in Figure A.

WATERPROOF WALL FINISHES
The materials most commonly used for shower walls are ceramic, marble or synthetic tiles, factory built
one-piece fiberglass units, and job-assembled fiberglass panels. The installation standards for each type
are provided below.

FACTORY BUILT ONE-PIECE FIBERGLASS UNITS
Factory built one-piece showers or tub/shower combination units must be installed following the
manufacturer’s printed instructions. Generally, factory built one-piece units can be installed directly to
unfinished framed walls without any backer boards (see Figure F).

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JOB-ASSEMBLED FIBERGLASS PANELS, MARBLE, OR ONYX
Factory built and job assembled fiberglass, stone or acrylic panels must be installed following the
manufacturer’s printed instructions. Generally, backer boards are not required by code (see Figure E).

TILE INSTALLATIONS
Ceramic, synthetic, and natural stone tiles are installed over an appropriate backing. Such backing can
be either a job built mortar bed or commercially available backer boards.

Mortar Bed: For mortar bed installations use water resistant gypsum board (green board) as a backer
board. The backer board must be covered with one layer of 15 pound asphalt impregnated felt. Metal
lath or 18 gauge stucco mesh must be nailed over the felt. Self-furring lath with integral building paper
can also be used. All fasteners must penetrate framing members. A mortar base is then applied forming
the mounting surface for the tile (see Figure J).

Cementatious Backer Board: (Two examples of commercially available cement board are DurockTM
and Wonder-BoardTM.) Framing must be covered with one layer of 15 pound asphalt impregnated felt.
Over the felt, fasten one layer of ½" thick cement board to the framing with 1½" galvanized roofing
nails or manufacturer approved corrosion resistant screws, no more than eight inches on center. All wall
joints and corners are covered with two inch wide vinyl coated glass fiber mesh tape and the tape is
embedded in bonding mortar (see Figure G).

Fiberglass Faced Water Resistant Gypsum Backer Board: (An example of a product is Dens-
ShieldTM.) This product consists of a water resistant gypsum core with glass-fiber mat facings. The
exposed side is additionally surfaced with a factory applied acrylic based coating. The board is ½"
thick. Boards are installed with the uncoated side toward the wall framing. Boards are attached directly
to the framing with 1¼" long Type W screws spaced 6" on center. Vapor barriers are not installed
behind this board. All wall joints and corners are covered with two inch wide glass fiber mesh tape and
the tape is embedded in adhesive (see Figure D).

Water Resistant Gypsum Board, aka “Green Board”: This product is not approved as a backing
board for shower enclosures using thin set tiles (see Figure H).

SHOWER PAN RECEPTORS
Shower pan receptors can be either factory built or site built. Bathtubs which have wall flanges can be
used as shower receptors. Self-rimming bathtubs which are placed on a platform cannot be used as a
shower receptor. All shower receptors must meet the following minimum standards:

•     All inside dimensions no less than 30". Bathtubs have an inside dimension of less than 30" but are
      excluded from this requirement. Standard 30" by 60" tubs can be used as shower receptors.

•     Shower receptors must have a floor area of no less than 1,024 square inches. Please note that a
      30 inch square (inside dimensions) shower has only 900 square inches of floor space.

•     Floor slope for drainage must be a minimum 1/4" to maximum 1/2" per foot.

(See Figures B and C for additional detail.)

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INSPECTIONS
For shower replacement projects which involve the installation of backer boards there will be three
inspections. For projects using factory built one piece shower units only two inspections are needed.

First Inspection: Made after all framing has been installed and/or repaired and before any backer board
or felt is installed. Any new piping or valve installations will also be inspected at this time. If a
site-built shower pan receptor is being constructed, it will be inspected during this inspection unless the
floor is being repaired. Plug the drain and fill the pan with water and let it sit until after the inspection.
If the floor is being repaired, it should be inspected along with the wall framing prior to the installation
of the site-built shower pan. The site-built shower pan will then be inspected during the second
inspection.

Second Inspection: Made after the backer board has been installed and all joints taped and sealed. For
mortar bed projects, an inspection is made after the vapor barrier and lath has been installed. For
projects using factory-built one-piece shower units this inspection is not needed.

Third Inspection: Made after all work has been completed.

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Tub and Shower Installations                     Page 4 of 5

                                                                                                    Min. inside
  Window w/ tempered glass
                                                                                                    Clear = 30"
                                                          Glassenclosure
              Flexible caulk

     Ceramic tile or other                                Waterproof                                       Fig
     waterproofmaterial.                                   wall finish                                      F

                                                                          enclosure = 70"
                                                                           Min. height of
           Slope to drain

               15#felt

    Backer board, Do                                                                               Drain
  not usegreen board                                       Curbheight
    under ceramic tile                                        3" to 9"

                  Figure A                                       Figure B (Section View)
            Window Sill at Shower                             Minimum Shower Dimensions

                                                               Ceramic or cultured marble
                                      Min. inside           tiles adhered to backer board
 Glassenclosure                       Clear = 30"
                                                                ICBO listed backer board
             Curb                                                  installedperapproved
                                           Min. 22"          instructions. Overlapflange

                                                              Shim so backer board can
                                                                      overlaptubflange
   Min. 1,024 sq. in. interior
 area measured fromface of                                 No 15# felt unless called for in
    wall or center of curb or               Outswinging       manufacturer'sinstructions
     face of glass enclosure                door
                                                                          Figure D
         Figure C (Plan View)                                   Tile on ICBO “Listed” Board
     Minimum Shower Dimensions                                                     (Dens-Shield,etc.)

    Full size plastic or fiberglass                         Greenboardoverlapsshower
   panels glued to backer board.                            flange. May need shimming
  Panels generally have no joints
                                                                         Shimif required
   except at inside wall corners.
                                                            Bottomedge of green board
                      Greenboard
                                                          shall be factory wrapped paper
     Bottomedge of green board                                              edge - no cuts
   shall be factory wrapped paper                                             Flexible caulk
                     edge - no cuts

              15# feltnot required                           Onepiecefiberglass/plastic
                                                                           shower stall

              Figure E                                                  Figure F
Single Piece Panels on Green Board                            One-Piece Fiberglass Shower
Tub and Shower Installations                                 Page 5 of 5

 Ceramic or cultured marble                   Ceramic or cultured marble
    tiles adhered to cement                    tiles glued to green board
                       board

Factory made cement board                         Water resistant gypsum
"Durrock" or "WonderBoard"                           board - Green board

15# felt or other ICBO listed
           water proof barrier

 Caulk for flexible water tight
                                                          Tub or shower pan
     joint - do not use grout

           Tub or shower pan

                 Figure G                                            Figure H
          Tile on Cement Board                                 Tile on Green Board
      (Example: "Durock" or "Wonderboard")                        (Not Permitted)

    Ceramic or marble tiles
       glued to mortar bed

   Mortar bed on metal lath

  15# felt or other approved
    water proof membrane

Caulk for flexible water tight
    joint - do not use grout

      Backer board, can be
    plywood or green board

                   Figure J
             Tile on Mortar Bed

                                              F:\Shared\PUBWRKS\BLDGINSP\BldgInspMasterDrawings\B-5 Drawing
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