How to regrout my shower and address moisture under tiles?

Question

We have some old grout in our shower floor that is not in very good shape. I set about re-grouting it by scraping out the old grout. In one small section, when I got down through the grout, there was wet, sandy grout and a small amount of water. The tiles feel solid and don't sound hollow underneath. The wet part is confined to about 3-4 cm of grout, and doesn't appear to have spread. The shower has not been used for a week.
My questions, is it normal to have a small amount of water underneath the tiles of a shower? From looking at construction diagrams it appears that it's normal to have a small amount of moisture below the tiles but above the waterproof membrane that naturally finds its way to 'weep holes' in the sides of the drain. Should I be talking to a tiler and get the whole thing ripped up? or just dry it out, re-grout, and seal it myself? Obviously the second option is cheaper but I don't want to be ignoring a potential big problem.

MitchellMc · Accepted Answer

Welcome to the Bunnings Workshop community @JMcE. It's fantastic to have you join us, and many thanks for your question about re-grouting a shower.

You're correct that this moisture should be sitting above the membrane layer and is of no real concern. As you mentioned, dry out the area and re-grout it. Don't forget the area down the bottom of the image to the left, there's a gap there too.

It's likely just residual moisture sitting on the membrane. Grout is not waterproof, so some moisture seeps through it and is captured by the membrane. Due to the gap, you just have a bit more sitting there than normal.

Unless water is escaping into the adjoining rooms, I don't think there is any cause for concern or need to rip all the tiles up.

Here's a helpful guide: How to grout tiles.

Please let me know if you have any questions.

Mitchell