Should I regrout or reseal my shower, or does it need rewaterproofing?

Tiles and grout are not the waterproofing. The membrane beneath them is. Grout is porous by nature, and a properly built shower assumes water will get through it and relies on the membrane to catch it and drain it to the waste.

Regrouting is likely to be enough when

• The problem is cosmetic, with staining or crumbling in the joints.
• There is no sign of water outside the shower enclosure.
• The tiles are firmly bonded, with no drummy or hollow sound when tapped.
• The shower is relatively young and was built with a compliant membrane.

It is probably the membrane when

• There is damp, staining, bubbling paint or lifting flooring in the adjoining room.
• Skirting boards near the shower wall are swelling or discolouring.
• Tiles sound drummy across an area rather than at one edge.
• It has been regrouted before and the problem returned.

Why the honest answer is expensive

Rewaterproofing a shower means removing the tiles and the screed to get to the membrane, so it is effectively a small rebuild. That is exactly why the cheaper recommendation is tempting, and why a repeated regrout that has not held is money spent twice. Waterproofing defects are among the most common causes of residential building complaints in Australia, which is a reasonable indication of how often the underlying work was inadequate to begin with.