How to fix grout that won’t set?

[Kirrily]

 

The grout in my shower was cracked so I’ve attempted to regrout. I removed the old grout, aiming to remove around half the depth. However, in some sections as I got deeper, the old grout started coming out like wet clay and came out right down to the screed (The shower floor consists of large tiles on top of screed, on top of the waterproofing).

Initially the exposed screed seemed very damp, like wet sand but since I’ve left it sitting for a while it seems to have dried out at least somewhat. 

The problem that I have now is that when I apply the new grout, it doesn’t set. It seems to be okay when applied to the sections with a few mm of the old grout remaining, but where it’s applied on top of the screed, it’s stays wet. I even tried to apply a very thin layer of grout on the screed and that won’t dry out either. 

I thought perhaps I could apply a hair dryer onto the areas of screed before the grout to give it longer to set before it sucks up more moisture from underneath. Another option maybe to apply grout sealer onto the exposed screed as a barrier before applying the new grout?

I’m in Canberra, so the weather might not be ideal. It’s quite cold in the bathroom. However, I did apply new grout to the shower walls and that set very quickly. Maybe I need to wait a few months for the screed to dry out completely?

Any ideas?

[EricL]

Hello @Kirrily 

Welcome to the Bunnings Workshop community. It's wonderful to have you join us, and thank you for sharing your question about fixing your grout.

Your analysis of the situation is quite correct, moisture trapped under the tiles and in the screed is preventing the grout from curing properly. Now you might be wondering, how come my wall grout cured straight away? That's because the moisture in your wall has gone down the wall and into your substrate.   

In order to accelerate evaporation, I suggest using a dehumidifier, please note that the basin waste must be covered, the floors emergency drain must be taped up and the shower waste covered as well. Keep your doors and windows closed. The dehumidifier will not draw in all the moisture in the room including the trapped moisture in the substrate.

When the substrate is dry enough you can then begin grouting. Generally, the common method of drying out your shower is to open the doors and windows to allow air circulation to carry out the moisture in the room. However, cold humid days will prevent the moisture from drying up.

Let me call on our experienced members @Adam_W and @homeinmelbourne for their recommendations.

If you need further assistance, please let us know.

Eric