The curb takes more water and more foot traffic than almost any other part of the shower, and it is where sloppy waterproofing shows up first. Here is how pros build a curb that stays dry under tile for the life of the install.
Foam Curb or Lumber: Pick Your Base
Prefabricated foam curbs have taken over for a reason: they are straight, dimensionally stable, and ready to waterproof out of the box. Lumber curbs need wrapping and furring and can twist as they dry, telegraphing cracks into grout lines. If the shower system offers a matching foam curb, use it. Find curb and pan components in the shower systems collection.
Anchor the Curb Without Breaking the Seal
Bond a foam curb to the subfloor with thinset or the system adhesive. If mechanical fasteners are required at the ends, seal every penetration with sealant and a patch. A screw through an unsealed curb face is a slow leak with a warranty claim attached.
Seal the Three Critical Joints
- Curb to pan: band the joint continuously, with preformed corners at both ends
- Curb to walls: carry the wall waterproofing down over the curb ends
- Top of curb: waterproof across the top so standing splash cannot find the core
Use the sealant and banding from the waterproofing collection that matches your board system, so every layer bonds to the next.
Slope the Top Toward the Shower
Pitch the top of the curb slightly inward so water sheds back into the pan, not onto the bathroom floor. Set the tile on the curb top with full coverage, no spot bonding, and finish the outside edge with a metal trim profile instead of a raw cut.
Shower Curb FAQ
How tall should a shower curb be?
Follow your local code and the pan manufacturer's spec. The common target is a curb that holds the pan's water level with margin, typically a few inches above the drain plane.
Can I skip the curb entirely?
With the right recessed pan and drainage plan, yes. That is a curbless build, covered in the curbless shower guide.
Why is my curb grout cracking?
Movement. Either the curb base is flexing or the tile was spot bonded. Rebuild with a bonded foam curb and full thinset coverage.
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