The Shower Curb is the First Line of Defense from Water Damage

The shower curb, while short in stature, has a very important job, it keeps the build up of water during normal and non-normal usage inside the shower area and out of the exterior bathroom. Typically, the minimum height of your shower curb is two inches above the shower drain, this protects from an overflow. Your design, structure, and completed shower curb will be dependent on a variety of factors.

Frame

The shower curb frame can be constructed of multiple 2×4 wood pieces to accommodate the entire entrance of the shower area. Pressure treated wood is a good choice for framework within the wet areas, but it has a high moisture content that will dry out and can be prone to twisting, therefore, you will need to determine if it is within the building code requirements in your area. Whether your bathroom is built on a raised foundation, second floor, or concrete slab, you can start the curb frame by screwing into place the first pre-cut wood piece, then each subsequent piece screwed into the previous until you reach your desired height. It is important to note that a 2×4 wood piece laying horizontally is 1/1/2 inches in height. Therefore, to reach a minimum height of 2 inches above the shower drain, you would need a total of ( 2 ) stacked 2×4 wood pieces to reach a total height of 3 inches, with 1 inch available for the installation of your pre-slope, top layer, and shower floor tile. There are also pre-manufactured shower curbs that can be purchased and modified to your exact shower area entrance dimensions. These pre-manufactured curbs offer a degree of simplicity for installation and protection from water seepage. Your preferences will dictate which option is best for you and the actual finish height, while also taking into account the finished tile over your shower curb.

Structure

While a solid wood frame will seem to be a solid structure for your shower curb, it still needs reinforcement to ensure the integrity of the entire curb serves it’s purpose of keeping water inside the shower area. There are many schools of thought as to how to provide structure to the shower curb, some are confident enough in modern building technologies to adhere backer board onto the curb as a final preparation for tile installation. Others fall into the more tried and true category of applying a cement coating using a mesh and a scratch coat. Neither is a wrong solution, but you need to understand how choosing one interacts with your entire shower pan installation.

Waterproofing

Before you provide structure to your shower curb, you need to apply your waterproofing method, sometimes called a water resistant barrier. Prior to starting your bathroom remodel, you chose a waterproofing method that consisted of a water resistant barrier that will be carried onto your shower curb. Water resistant barriers come in many forms and applications, under a standard waterproofing application, the shower curb is secured to the wood or concrete slab floor, then the water resistant barrier is applied inside the shower area, up and over the shower curb. The water resistant barrier can consist of a pan liner, which is made of a single PVC material, an asphalt and felt paper combination, which is often called a hot mop, or a sheet membrane, which is a material that is cut to size and at the joints they are mud packed. There is also a liquid membrane, which is painted or rolled onto the shower curb, but in this case you would need to have a paintable, preferably a flat surface already constructed, such as a backer board or cement over the curb.

Cement Over Curb

An application of cement over your shower curb is a very well respected and secure way of completing the structural integrity. Taking into consideration the waterproofing method that you have chosen and installed over the shower curb, a wire mesh is formed over the waterproofing and across the entirety of the curb. With the mesh formed over the shower curb, a cement scratch coat is applied to the mesh to form the exterior of the shower curb. The scratch coat commonly consists of deck mud or concrete, with a consistency of either peanut butter or easily balled up into your hand. This is going to be the base for your tile to be adhered to.

Backer Board Over Curb

Another option for completing the structural integrity of your shower curb would be to install backer board over the curb. By virtue of the installation process, using screws that pierce the water resistant barrier on the sides and on top of the shower curb, there is an argument that the waterproofing integrity has been compromised. While true, if just left as is after installation, in this case your waterproofing strategy will take this into account. First, if your choice as a base for your tile installation is going to be a backer board, then the most secure way to adhere it to the shower curb would be to screw through the water resistant barrier. The least amount of screws used on the interior of the shower curb the better and they should never be less than 2 inches from the height of the shower drain. Local building codes would determine what is an acceptable height. Where punctures have occurred in the backer board from screws that were installed, mud pack the openings with a thin set, deck mud, or silicone. You can further use a fiber mesh over packing and to further protect the exterior from water seepage, you can apply a liquid waterproofing membrane over these punctures

Since there are many components that make up a functional shower curb, looking at each in relation to your overall plan will help you making the best decisions during the construction of your bathroom remodel.

Kirb-Perfect® Shower Curb

Kirb-Perfect® is a stay-in plastic form designed to eliminate the possibility of any nails puncturing the liner on the top or inside walls of shower curbs.

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