Stained grout is what you see. The waterproofing is behind the tile. Cement grout is not a waterproof membrane. Regrout when the field is seated and the damage stays in the joints. Stop when tiles sound hollow, the wall flexes, or the adjacent room shows staining.

What regrouting can and cannot do

Regrouting can refresh color, replace crumbling joints, and reduce water sitting in open lines. It does not repair rotten framing, saturated drywall, or a failed pan. New grout over a wet cavity can trap moisture.

Corners and fixture edges are usually caulk, not grout. Do not grout a change-of-plane joint.

Three different surface clues

Mildew in grout: cleaning may handle light spotting if the wall is solid. Mildew that returns through the joint after cleaning is a moisture-path clue. It is not a ranked “most common complaint” statistic.

Hairline grout cracks: settling, mix, or movement. Small cracks can still pass water.

Hollow or tented tile: the bond has failed. Do not start a DIY kit. That is tile repair.

Older San Diego showers were often set on moisture-resistant drywall rather than a modern membrane. That construction history is real in many mid-century tracts. It does not prove your wall is green board. Use the tap and press tests.

Fresh light grey grout being floated into shower tile joints with a rubber float

Sanded, unsanded, color, sealer

Manufacturer joint-width rules still apply: sanded grout is generally for wider joints; unsanded for narrow ones. Confirm on the bag. Color on the bag is not the cured color. A test patch is the only visual check. Sealer on cement grout is a product step, not a timed 48-hour rule unless the label says so.

DIY kit versus a pro quote

Hardware-store kits exist. They are not automatically safe. Grout removal dust, blade slip, and a misread hollow tile are the usual failures. Fix Pro San Diego does not publish a materials total, a DIY hour count, or a county grout price range.

Ask a matched professional for a written scope: spot joints, full enclosure, or tear-out if the substrate fails.

A five-minute inspection before anyone buys a bag

  1. Tap every tile. Hollow or clacky marks belong on tape.
  2. Press corners, faucet wall, and lowest courses. Flex is a stop.
  3. Confirm corners are caulk, not hard grout.
  4. Check the room on the other side of the valve wall for stains.

If the shower fails those checks, skip the kit.

Confirm current CSLB and local permit rules for the proposed contract. Check a contractor on the CSLB site before you hire. A shower rebuild is a different request from joint-only grout.

Call (858) 400-4611. Fix Pro San Diego matches you with licensed, independent local pros. It does not regrout showers.