Shower pan choices, installation, troubleshooting:

This article discusses the proper construction or installation of cement, pre-fab, or mortar-bed shower pans and shower pan membranes to build a leak-proof shower floor.

Recommendations for Constructing or Installing Bath Shower Pans

This article series discusses current best design practices for kitchens and bathrooms, including layout, clearances, work space, and accessible kitchen and bathroom layout, clearances, turning space, grab bars, controls, etc.

We include advice on choosing and installing kitchen countertops, cabinets, and kitchen or bathroom flooring, sinks, and other plumbing fixtures and fixture controls such as faucets. A list of kitchen and bath product manufactures and sources is included.

The fiberglass shower pan shown at left was placed and secured to the floor during bathroom construction, then protected from damage with cardboard pending installation of shower enclosure, plumbing, controls, and door.

As explained in Chapter 6 of Best Practices Guide to Residential Construction (Steve Bliss, J Wiley & Sons) :

A shower pan must be completely watertight and able to hold pooled water should the drain get clogged.

Most are built in place over a mortar bed with a waterproof membrane liner.

However prefabricated setting beds have also become available recently.

Guide to Using Prefab Cement Shower Pans

Our collapsing, leaking shower pan/floor installation (left) illustrates why site-built lead lined shower pans are a "lost art" and why most contractors opt for pre-fab shower pans of cement, fiberglass, or other materials.

For standard shapes and sizes, one option is to install a prefabricated pan made from 40-lb polystyrene foam coated with a reinforced cementitious coating that is ready to receive tile.

These range in size from 36x36 inches to 36x60 inches and come pre sloped with a built-in drain.

One unit, called Pro-Form (Bonsal American) is bonded to the subfloor with latex modified thinset, coated with a liquid waterproofing membrane, and is then ready to tile.

As long as the subfloor is sufficiently stiff to prevent flexing, these units should perform well with 4x4–inch tiles. Smaller tiles may exert too much of a point load for the underlying foam, while larger tiles can cause problems with the slope angle.

How to Install Prefab Plastic Shower Pans

A less expensive option is to combine tiled walls with a one-piece fiberglass or acrylic shower pan (not to be tiled). These are the same materials used in one-piece shower or shower-tub units. A few companies also sell stand-alone solid-surface shower pans.

Like other plastic units, these must be properly supported underneath to prevent flexing and cracking. Some require setting in sand, wet mortar, or plaster. In general, acrylic units cost more than fiberglass but are stronger and less prone to flexing and cracking.

How to Build Mortar-Bed Shower Pans & Install a Shower Pan Membrane

Built-in-place shower floors using a mortar bed and modern waterproofing shower pan membranes can provide many years of trouble-free service. For best performance use a heavy-duty sheet membrane, such as 40-mil Chloraloy (Noble Company), which is designed for use in shower pans and similar applications.

To guarantee that any trapped water will drain properly, the shower pan membrane is placed on a layer of latex-modified mortar sloped 1/4 inch per foot toward the drain.

Two-piece clamping-type drains are designed to seal to the membrane by compression between the upper and lower flanges (see Figure 6-41).

Figure 6-41

[Click any image or table to see an enlarged version with additional detail, commentary & source citation.]

A layer of sealant applied between the shower pan membrane and lower flange serves as backup waterproofing. Weep holes around the bottom of the drain, surrounded by pea gravel or pieces of broken tile, allow any water that accumulates to drain away (see Figure 6-42 below).

The shower pan membrane should run up all sides of the shower, at least 3 inches above the height of the finished curb.

Secure the membrane to the framing with galvanized staples or roofing nails along the top edge, being careful to make no holes in the membrane any lower than 2 inches above the finished curb.

At the inside wall corners, the extra membrane material is not cut, but pleated and folded over to lay flat against the framing. Avoid making wrinkles here or along the bottom of the pan.

At the curb, the membrane must be cut so it can fold over the top of the curb. Seal these corner cuts with either prefabricated “dam corners” or patches of membrane caulked in place with Nobleseal 150, a high-performance Kraton-based sealant.

Figure 6-42

Kitchen and Bath Product Manufacturers, Sources, Associations

• Bonsal American www.bonsal.com Setting compounds, grouts, preformed shower pans, curbs, and niches. Also, distributor of backerboards, isolation membranes, and other tile-setting products
• Color Caulk, div. of Roanoke Companies Group www.colorcaulk.com Color-matched caulking
• Custom Building Products www.custombuildingproducts.com Elastomeric and liquid-applied membranes, self-leveling underlayments, setting compounds, and grouts
• Laticrete International www.laticrete.com Trowel-on membranes, self-leveling underlayments, setting compounds, grouts, and sealants
• Noble Company www.noblecompany.com CPE sheet membranes, trowel-on membranes, clamping ring drains, and preformed slopes, niches, and curbs
• Mapei www.mapei.com Trowel-on and sheet membranes, self-leveling underlayments, setting compounds, grouts, and color-matched sanded caulks
• Custom Building Products www.custombuildingproducts.com Wonderboard cement backerboard, Easyboard cement and polystyrene lightweight backerboard, and Rhinoboard fiber-cement backerboard
• Georgia-Pacific Gypsum www.gp.com/build Denshield gypboard backer with glass-matt facing
• James Hardie Building Products www.jameshardie.com Fiber-cement backerboard
• National Gypsum www.nationalgypsum.com Permabase lightweight cement and polystyrene backerboard
• Schluter Systems www.schluter.com Kerdi tile membrane goes directly over drywall or other substrates
• T. Clear Corp./Fin Pan Inc. www.finpan.com Util-A-Crete lightweight concrete backerboard
• U.S. Gypsum www.usg.com Durock cement backerboard
• W. R. Bonsal www.bonsal.com Extruded polystyrene backerboard with fiberglassreinforced cement facing

-- Adapted with permission from Best Practices Guide to Residential Construction (Steve Bliss, J Wiley & Sons) .

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2020-03-19 - by (mod) - don't confuse shower pan liners & membranes with peel-and-stick flashing membranes

Richard:

Thank you for the comment.

Indeed it's important to distinguish between peel-and-stick flashing membranes used on building exteriors and shower pan liners and membranes as they are different products with different requirements.

If you have an application that needs to hold standing water I'd recommend either using EPDM (rubber roofing) outdoors, or if protected by a finish surface, a shower pan liner rated for that use.

Indeed flashing membranes like those described at FLASHING MEMBRANES PEEL & STICK, aka "peel and stick membranes," are intended for use on buildings in areas that drain water away such as around windows and doors and as a sloped roof underlayment or valley liner.

Most of those products are not intended for use in showers as a shower pan liner and will fail in that location.

However there are a number of shower pan liners intended specifically for that use, typically 40 mil PVC membranes that are set in place, folded up at edges and corners, and where needed, adhered in place using a special PVC cement such as that provided by Oatey.

Examples of Shower Pan Liners and similar products that can tolerate standing water include:

BetterBath RV Shower pan liner membrane
Compo-Tite shower pan liner
Goof-Proof Waterproofing sheeting
Kohler K-8458 shower pan liner membrane
NobleSeal thinset TM shower pan liner
Oatey No. 41620 40 mil PVC shower pan membrane liner - shown below
Oatey "Perfect Brown" shower pan liner
Schluter Kerdi shower pan liner
Wal-Rich shower pan membrane

And there are paint-on waterproofing pan liner materials such as

Laticrete HydroBan waterproof membrane

Here is Oatey's PVC adhesive for shower pan liners

On 2020-03-19 by Richard McLauchlan

Shocked to discover many peal stick membranes (none torch on) are not designed warrantied to hold standing water! sill pan protection not

This Q&A were posted originally at FLASHING MEMBRANES PEEL & STICK

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Continue reading at CERAMIC TILE FLOOR & WALL or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• BATH & KITCHEN DESIGN GUIDE - home
• CERAMIC TILE FLOOR & WALL
• FLASHING MEMBRANES PEEL & STICK
• SHOWER PAN INSTALLATION & LINERS
• SPAS WHIRLPOOLS SOAKING & JETTED TUBS
• TILED WALKING SURFACE SLIP HAZARDS

Suggested citation for this web page

SHOWER PAN INSTALLATION & LINERS at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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