Shower and shower pan construction is a typical concern for many.  We have received 13 home repair calls on this topic alone in the past month.  We have found that typically installers simply do not understand the installation practices.  This is a topic for homeowners to be concerned about.  The cause and effect if improper shower pans are shocking – especially the causes:

number 1 cause of shower pan failure :   improper wrapping of membrane over 3 1/2″ entrance curb

number 2 cause  :  improper bench seat installation

number 3 cause  :  improperly placed fasteners at pan perimeter (must be up 8″)

number 4 cause :  torn/punctured pan during tile/shower door installation

number 5 cause : clogging secondary drain at mud pan level (there is one in every shower pan drain system)

The proper procedure (as per NC and International Codes and Inspectors) :

Remove old shower pan if applicable (If new construction skip to #5 below)

1.  Remove tiles and dur-a-rock 12″ up from tile shower floor including curbing tile and 12″ above curbing tile (existing pan replacement)

2.  Remove shower floor tile, mud base and membrane to expose subfloor

3.  If subfloor is damaged it must be removed and replaced with 3/4″ cdx or treated plywood.  If not damaged then proceed to #4

4.  Install additional layer of 1/2″ or 3/4″ plywood on top of existing fastening with screws and adhesive to make shower floor rigid.  (This is a common practice for installers to simply leave 1 layer but we prefer 2 layers for obvious reasons)

5.  Install 2×4 blocking between studs on walls on edge to create a mini wall to allow control of mud pan and fastening of membrane

6.  use 2′ or 4′ level from adjustable drain top to walls in every direction.  Mark on walls the amount of slope desired (minimum 1″ of fall per 12″ of travel towards the drain: typical)

7.  Mark walls/blocking where your slope is to begin.

8.  Mix shower floor mud to consistency as directed on bags.  Pour mud pan directly onto shower floor plywood.

9.  Pull floor mud from drain towards marks on wall to achieve your desired slope.  Make sure that corners are cut in to accept both side angles and forms a valley type form.  This preslope does not need to be perfect as there are a few steps before prep is complete.

10.  After 24 hrs dry time have licensed plumbing contractor, familiar with shower pan installation, install the membrane pan.  You will notice that the membrane runs up walls 10″ around perimeter with corners overlapped and glued(not cut).  The membrane should run up and over the complete curbing system.  Patches need to be installed at curbing to wall transitions.  Ensure that membrane wraps around the framed opening above the curb which ties into shower walls and overlaps curb ends by a minimum of 6″ overlap each direction.  These overlaps must be glued using glue by the same manufacturer as the membrane.

11.  Fasten membrane 8″ up from pan(membrane) base on walls, around the framing openings on the outside of the shower and at the curb on the opposite side of the shower.  Use galvanized roofing nails to secure or manufacturer recommended fasteners.

12.  If replacing an existing shower pan, install dur-a-rock on walls and thinset joints using thinset and mesh tape.  If new shower then proceed to #13.

13.  Install drain plug and fill membrane shower floor with water to test for any possible leaks.  Leave shower floor membrane filled with water and, very important, CALL FOR ROUGH IN INSPECTION FOR SHOWER PAN.

14.  Remove water from pan after inspection and install the adjustable drain system.

15.  Install dissolving tissue paper or small pebbles around secondary drain system (weep holes) to avoid clogging.  This is extremely important as if you clog the secondary drain water will accumulate under the tile and either cause tiles to lift, allow mildew growth under tile and cause the grout in shower floor tile to lift continuously.

16.  Install additional floor mud coating over pan, which is now presloped,  to a thinner layer to parallel the pre slope.  Allow 24 hrs of dry time.

17.  Paint coating of “Red Guard” over entire shower pan mud coating and up walls to height of top of visible dur-a-rock (when replacing existing shower pan).  In new construction of shower coat all- walls, mud pan, curb, etc.

18.  Install shower floor tile and curbing tile.  Shower floor tile should be small enough to accept sloping and valleys.  Most manufacturers recommend 2″ tile.  In larger showers larger tiles can be used.

19.  Install wall tile which will be installed so that the bottom of the tile will cover the edge of the cut floor tile.  This will allow proper water channeling towards the drain.  In tile work always remember that it is best to mark on the walls and floor to ensure a successful outcome and overlapping tiles to avoid cut tile end visibility is common practice.  This will avoid sharp edges and a much better looking end result.

20.  Adjust the adjustable drain so the flat drain top is at the same height as the finished floor tile.  Grout shower floor and wall tile.  Remember to allow the tile to set 24 hours before any pressure or grouting is permitted.

21.  Install clear sealant to all 90 degree tile joints to allow for a long term beautiful project.  ie: wall to floor transition and wall to wall corners.

Note: Whenever installing a shower door it is always recommended to never install screws at base/threshold.  Instead use a silicone or urethane sealant.  Install bead of sealant, set threshold then smooth sealant for a cosmetically appealing caulk line.  The sides should be installed with screws.  Remember when drilling through the tile for the door side pieces(tracks) to fill drilled holes with sealant prior to installation so the holes will be sealed and compressed with sealant when the track is installed.

The effects of an improperly installed tile shower -pan(membrane), curbing, shower door, and adjustable drain system are endless.  They range from mold buildup and water accumulation which travel, over time, past the shower envelope to joist damage, girder damage, subfloor damage, shower framing damage and moisture into a crawlspace.  The most effective ways to prevent these from occurring are to have a qualified company evaluate or perform the tile shower installation and to obtain a plumbing permit which will consist of 2 inspections:  a plumbing rough in shower pan inspection and then a final plumbing inspection once all items listed above are complete.

We hope that this topic is helpful to homeowners and other home maintenance and home repair contractors and will alleviate many sleepless nights and many unnecessary dollars spent.

Tags: home, home repairs, new construction, structural issues

This entry was posted on Saturday, December 12th, 2009 at 12:27 pm and is filed under Home Repairs, New Home Builders, Wilmington NC. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.