What is the divot method?
The divot method is a way to utilize a regular three piece clamping drain with a topical waterproofing product. Topical waterproofing includes sheet membranes such as Schluter Kerdi and liquid membranes such as Laticrete Hydroban or Custom’s Redgard.
What you need to know:
If you are familiar with waterproofing a shower floor with Schluter Kerdi, or any other topical membrane, including liquids, you know that you need a topical drain. These differ from a regular clamping drain because they do not have an integrated weep system.
Don’t have any idea what that means? Then you need to do more research before you attempt to build and waterproof a shower floor. Seriously. You need to know what you are working with before building a waterproof box (your shower) inside of a wooden structure (your house) and expecting it to prevent damage that could compromise the structure (your bankruptcy). You can start with my free waterproofing manual. It will give you good overall information on the various waterproofing methods.
A clamping drain has integrated weep holes below the barrel, or central, part of the drain. Any water that does not go into the top of the drain (the strainer, the portion you see) will make its way down to the weep holes and into the pipe. A topical drain channels all water into the top of the drain. If you DO know what that means, then I’ll explain how you can use a 3-piece clamping drain with a topical waterproofing membrane. That’s what you’re here for, right?
The way to use a clamping drain with a topical waterproofing membrane is with what is called the ‘divot’ method. The divot method is a way to tie the weep holes in the drain, which are BENEATH the top of the deck mud, into the waterproofing on top of the shower floor.
The ‘divot’ is exactly what it sounds like – an impression around the drain. The sides of this impression slope from the top of the shower floor (where the waterproofing is installed) down into the weep holes of the clamping drain. By tying the waterproofing of the surface membrane into the waterproofing down the sides of the divot and into the weep holes any water not entering the top of the drain will run down into the weep holes. This divot, once waterproofed, is filled with deck mud.
The shower floor utilizing the divot method will look something like this horrible graphic here:
And here’s what it looks like with a liquid membrane as the waterproofing.
If you are using a sheet membrane it is best to use what is called a ‘hat’. This is a membrane material formed in the shape of a…wait for it…hat! A sombrero, specifically…
It comes without the hole in the center, you need to cut the hole to fit against the outside of the bolts in the lower flange of the drain.
This is installed with thinset, just like the kerdi membrane, and once cured forms a waterproof seal from the surface down into the weep holes. One of the most common products used for this is the Nobleflex drain flashing (the gray things in the photos above). It is available in five sizes, the two most common being ¾” or 1 ½”. This indicates the depth of your mud bed at the drain. So if your mud deck is 1 ½” deep at the drain, you need the 1 ½” drain flashing.
You can use nearly anything to form the divot in the mud. A small frying pan, a mixing bowl, if using a hat you can place it down there and just pack mud around it. Anything that will form that impression will work just fine. I highly recommend the drain flashing tool. It is that pink foam thing you see in the photo below. It works really well.
You can also use a liquid membrane if you are using a sheet membrane over the floor. You just paint the liquid from the weep holes up the sides of the divot and onto the surface of the sheet membrane.
Whichever method you choose you need to ensure that your waterproofing is installed directly up against the outside of the bolts in the lower flange of the clamping drain and is then sandwiched between the upper and lower flanges exactly like a regular membrane would be. This way water will flow from the surface membrane down into the divot and into the weep holes. You want a continuous layer of waterproofing from the surface of the shower floor all the way into the weep holes.
The graphic below shows an exploded view on the right and the way it all fits together on the left. See how the membrane is sandwiched between the upper and lower flange? Like that.
Once the waterproofing is completed you need to place something around the drain flange to ensure that deck mud does not block the weep holes. Pea gravel works very well, as does a ‘weep hole protector’ (it’s that clear thing you see in the photo below).
Once that is in place just fill the divot with deck mud flush to the top of the shower floor and tile directly over it up to the drain. DO NOT waterproof over the top of the deck mud filling the divot! That seals up the weep holes and defeats the entire purpose of all this work.
The short list of steps necessary for the divot method:
Assuming you already have the basics down as far as creating a shower floor for tile (click that link – it’ll give you the overview), there are only a few differences. If you read through that link above, the one for the regular shower floor (traditional liner method), the main difference is that you only need a single slope, or the preslope. Once created your topical waterproofing will be installed directly to that.
Before you begin packing mud for your shower floor you need to have the drain installed with only the lower flange of the drain assembly. You then place your divot ‘form’, whatever you’re using to form the divot – pan, mixing bowl, the pink foam divot tool I mentioned above, etc. – over the lower flange in order to pack mud against it to form the divot.
Then just pack all the mud in there as you normally would for the preslope (in the link above). Be sure to pack it well against your divot form so that once cured the walls of the divot are solid.
Once the deck mud is cured, remove your divot form carefully. It is usually better to slowly twist it back and forth out of the divot rather than trying to pull it straight up. You should have a (fairly) perfectly formed divot around the lower drain flange.
Pretty, isn’t it? 
Then…
If you are using a topical liquid as your waterproofing:
Just paint the waterproofing liquid with the required thickness over the entire shower floor, including down into the divot and ONTO THE LOWER FLANGE OF THE DRAIN, up to the opening.
Once you have the required coatings and they are cured, install the top half of the drain flange, put your weep hole protection in there (pea gravel, weep protector, etc.), insert the threaded ‘barrel’ portion of the drain then fill the divot with deck mud flush to the top of the shower floor.
If you are using a sheet membrane as your waterproofing with the drain flashing:
Cut out the hole in the flashing (hat) to fit snugly against the outside of the bolts in the lower drain flange. Install a silicone bead around the outside of the bolts onto the lower drain flange. Comb thinset from the perimeter of the drain flange, up the sides of the divot and out onto the shower floor enough to reach the edges of the flashing once installed.
Place the flashing (hat) down onto the drain, press firmly around the flange in order to embed it into the bead of silicone. Embed the rest of the flashing into the thinset around the drain, up the sides of the divot and out onto the shower floor. Install the upper flange of the drain assembly and tighten down the bolts.
Install your sheet membrane onto the shower floor and over the edge of the drain flashing, all the way up to the very top edge of the divot (where it meets the shower floor).
Once finished place your weep hole protection into the divot around the drain flange (pea gravel, weep protector, etc.), insert the threaded ‘barrel’ portion of the drain then fill the divot with deck mud flush to the top of the shower floor.
If you are using a sheet membrane on the floor with a liquid waterproofing for the divot:
Begin by installing the sheet membrane over the shower floor up to the very top edge of the divot where it meets the shower floor. Once that’s installed paint your waterproofing membrane from the very edge of the drain opening on the lower flange all the way up the divot and onto the membrane on the shower floor a minimum of four inches around the outside of the divot. Repeat with as many coats as needed to achieve the required thickness of the liquid membrane.
Once you have the required coatings and they are cured, install the top half of the drain flange, put your weep hole protection in there (pea gravel, weep protector, etc.), insert the threaded ‘barrel’ portion of the drain then fill the divot with deck mud flush to the top of the shower floor.
These are the very basic steps for utilizing a three piece clamping drain with a topical waterproofing. I can answer any specific questions below, because not every project is going to be so basic and every installation will have different aspects. I obviously can not cover every scenario in one blog post, but I will help if you ask a question in the comments.
If you need instructions on the rest of the steps for your shower installation with topical waterproofing membranes just head on over to the Library and pick up one of the manuals for your specific shower. We have every waterproofing type in there and each manual is detailed from the start of your project to the finish.
With, of course, some horrible humor and adult beverages thrown in. Because when you’re building a shower – you absolutely need both!
