What is a shower tray upstand, and do I need a seal kit?
Why silicone alone at the tray-to-wall joint is a single point of failure, what an upstand and a seal kit each do differently, and when you can and cannot add one.
- Difficulty
- intermediate
- Time
- 25 min
- Read
- 4 min
Short answer
An upstand is a raised lip moulded into the tray that the tile finishes in front of, so water is thrown back into the tray instead of relying on the silicone. A seal kit is a strip fixed to the wall before tiling, with one leg buried behind the tile and one turned down into the tray, so it still works when the silicone has failed. Both are fitted before tiling — neither is retrofittable without taking tiles off.
The joint where a shower tray meets a tiled wall is the wettest joint in a house and, in a great many bathrooms, its entire waterproofing is one bead of silicone applied by somebody in a hurry. When that bead cracks, or is stretched by a tray that moves, the water goes straight down behind the tray where nothing stops it and nothing dries. Upstands and seal kits both exist to make the silicone the second line of defence rather than the only one. The cross-section drawing shows all three arrangements together.
Step by step
- Understand what happens with silicone alone.Tile finishes above the tray, the gap between is filled with a bead, and every drop of water running down the tile arrives at that bead. It works while it is perfect. The moment it cracks, ages, is stretched by a moving tray or was applied over a dirty joint, water passes it and enters the void under the tray. Nothing under there sheds it and nothing dries it.
- Understand an upstand.Some trays are moulded with a raised lip, typically twenty to thirty millimetres, along the edges that meet a wall. The tile is set to finish in front of the upstand, not above it, and the silicone bead sits at the top of the upstand. Water running down the tile now lands on the front face of the lip and is thrown back into the tray. The bead becomes a backup.
- Understand a seal kit.A proprietary strip or trim fixed to the wall before tiling. Its lower leg turns down into the tray; its upper leg is buried behind the tile adhesive and covered by the tanking. Water that gets behind the tile at any point is intercepted and returned to the tray. This is the only one of the three that is still watertight when the visible silicone has failed completely.
- Work out which you have.Look at the joint. If the tile bottom edge sits above the flat of the tray with a bead in between, you have silicone only. If there is a visible raised lip on the tray with tile in front of it, you have an upstand. A seal kit is invisible once tiled, so if you did not fit it and the bathroom is not new, assume you do not have one.
- Be realistic about retrofitting.Neither can be added without removing at least the bottom two courses of tile, because both have to sit behind the tile. Anything sold as a retrofit upstand is a surface-mounted trim siliconed on top, and that is a third silicone joint rather than a second line of defence. It is better than nothing and it is not the same thing.
- Get it into the plan if the tiles are coming off anyway.If you are retiling, replacing the tray, or dealing with a leak that has already got behind the tiles, this is the moment. The cost of a seal kit is trivial next to what a repeat leak costs, and the labour is already being paid for.
- Do not treat either as a substitute for tanking.A seal kit protects the tray junction. Tanking protects the whole wall. In a shower area, tile onto a suitable board and tank it, then fit the seal kit at the tray, then tile, then seal. They are layers, not alternatives.
- Seal the finished joint properly regardless.Whichever arrangement you have, the visible joint still gets a proper sanitary silicone bead: joint cut out completely, dry, tray loaded with a person standing in it if it is a tray that moves at all, one continuous pass, tooled once.
Common mistakes
- Tiling down over the top of an upstand — It defeats the upstand entirely. The tile has to finish in front of the lip so water lands on the lip's face, not behind it.
- Treating a stick-on upstand trim as equivalent to a seal kit — It is a second silicone joint on the surface. It helps cosmetically and it is not a concealed drainage path.
- Fitting a seal kit and skipping the tanking — The kit handles the tray junction. Water getting through grout higher up the wall goes into the board and past the kit.
Questions people ask
Is a tray with an upstand worth paying more for?
Yes, if you are buying a tray anyway. It removes the most common bathroom leak path for very little extra, and it is only available at the point of purchase.
Can I fit a seal kit to an existing shower?
Only by taking the lower tiles off. Anything else is a surface trim. If the lower tiles are coming off because of a leak, fit one while they are off.
Which matters more, the upstand or the tanking?
The tanking, because it protects the whole wet wall. But the tray junction is where the water concentrates, so a tanked wall with a bare silicone tray joint still has one weak point.