Repair Leaky Floor Pan
This section is designed to detail the method for replacing only the shower pan where it is not desirable or practical to replace the entire shower. Details of tile setting are omitted as they are covered in the section on Showers and Tubs and "Bathtubs".
The leaking shower pan membrane may be made of any of the materials listed in the section on Showers and Tubs. The first step to always consider is determining exactly what is leaking. Be sure that a pan replacement is necessary and the problem cannot be fixed with a less expensive plumbing job.
In the case at hand, we see a shower built in the 1950's. This leaking pan may have gone undetected for years and probably did. This was due to this residence having a raised foundation that resulted in the leaking water simply draining under the house. The problem was discovered by the owner crawling under the house investigating an unrelated problem.
We can see, however, from the clearly evident crack in the shower floor that something was wrong and further investigation was required.
Be sure to wear appropriate safety devices. In the following example a dust mask, hearing protection, gloves, and safety glasses were necessary. Pick a grout joint that is at least 3"-6" above dam height to begin cutting the tile and substrate (mortar in this case).
Tile Doctor Tip: The reason for the minimum 3"-6" height is that the replacement pan is required to be at least 3" above dam height to meet current industry standards. Remember to think ahead. The new shower pan will extend 3" above dam height. There will also need to be room for fastening the reinforcing wire covered later in this section.
Cut all the way around the installation horizontally being sure that the depth of the cut is sufficient to cut the reinforcing wire in the mortar. Be sure not to cut the tile above the joint, as they will remain when new mortar and tile are installed.
Carefully remove the tile and mortar below the kerf using a hammer and pry-bar. Sometimes it is necessary to use only the hammer and simply break out the tile and mortar. This is especially true with the mortar shower pan.
This process exposes the wall studs and sub-floor beneath the shower pan. It is now possible to determine why the pan was leaking. Basically the shower pan had totally disintegrated. There were factors that caused this situation that are avoidable by following current industry standards.
The reasons for the shower pan failure were:
The pan was constructed of an asphalt-impregnated paper, not three layers of hot tar and 15lb roofing felt reinforced at the corners.
- There was no pre-sloping on the floor beneath the shower pan.
- The shower pan material did not extend 3" above dam height.
- The pan and reinforcing was stapled through the top of the dam.
- The weep holes in the two-piece shower drain were completely blocked with mortar.
- There was no blocking behind the pan against the wall studs.
- There was no reinforcing wire in the shower pan mortar bed.
Tile Doctor Tip: The seven points mentioned above are key elements that can spell the success or failure of shower pans that are used in tile lined showers. This applies to hot mopped pans or the flexible membrane pans currently in industry use.
In this particular job it was necessary to replace the entire shower as the walls and tile bond had completely failed.
Once the old material is removed, the necessary repairs are made to any damaged structures. Refer to Replace Water-Damaged Sub floor for more on that topic. Once the framing has been repaired, the plumbing is replaced.
At this point, a new shower pan membrane properly installed over a pre-sloped floor. The new shower pan membrane is water tested for 24 hours as detailed in the section on Showers and Tubs.
At this point, the new shower pan membrane is drained and should be protected while reinforcing wire is attached to the studs and backing without stapling through the membrane.
New wall mortar is applied using a sort of template that will act as a screed to cut the mortar to the necessary depth to allow new tile to be installed. The idea of the template is to keep the new mortar on plane with the old mortar with sufficient depth to allow thin set and new tile to be installed on plane with the existing tile.
Once the wall tile is reinstalled, the floor mortar is installed with the necessary reinforcing while the weep holes are kept open with crushed tile or small stones. The floor is then tiled.
The tile is grouted and the necessary joints are left open for sealant instead of hard grout. These joints are filled before or after the grouting.