How to fix cracking grout between shower base and tiles?

Hi all,

About 12 months ago I got some tilers in to redo the grout for our shower. Slowly over the last 12 months the grout has cracked and has been crumbling away only along the bottom edge between the tiles and the shower base. Prior to the tilers fixing, the bottom edge was previously grout as well.

I have read opposing advice online regarding regrouting vs using silicone to repair. At the time, the tiler said that there was a lip on the edge of the shower base behind the tile that would prevent any water getting into the wall cavity. Even if this were the case, surely this cracking should be repaired?

Any advice on the best method to repair is appreciated! Thanks!

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Jason

Hi @dyfuse,

Let me tag our resident Bunnings D.I.Y. expert @EricL to assist you as soon as possible.

Other experienced members like @MikeTNZ, @TedBear and @Jewelleryrescue might also like to add their thoughts in the meantime.

Jason

EricL

Hello @dyfuse

It is a bit concerning that the grout has deteriorated this fast. Generally speaking, the grout usually lasts longer even when exposed to heavy moisture. If the shower regrouting is still under warranty, I suggest calling the tilers back to repair the damage.

If they insist on using grout again, I propose sealing it up using Dunlop 250ml Grout Sealer. This will extend the grouts service life and prevent it from being contaminated by moisture. However, if you are given a choice, I recommend using Selleys 300g White Wet Area Waterproof Silicone Sealant. It is much more tolerant of temperature and moisture change in the bathroom.

If it is out of warranty, I suggest having a look at this guide and try to apply the silicone yourself- How to silicone seal a bath. The technique used is applicable to your current project. Please note that the old grout will need to be removed before you apply the silicone seal.

If you have any other questions we can help with, please let us know.

Eric

Jewelleryrescue

Hi @dyfuse

I Think @EricL will work well but a sealer solution to the base might last longer and resist future movements.

The base will naturally move and flex everytime you use it basically too much movement for grout to cope with as you discovered. The reason you mainly need to repair it is that the crack is a haven for mold spore growth. and moisture can get behind the tiles and loosen the glue eventually. Unless my eyes and monitor are missleading me I am seeing a purple tinge on the joins which will be a type of fungi out of the million plus species so please start hitting that area with exit mold tpye products, The best way to kill mold spores is with a steam cleaner if you have one the high heat does wonders at cleaning and steralising.

As you mold clean you will need to pull out with a small flat screw driver or at a pinch butter knive all the loose grout you can so you can replace it.

The only down side to some silicone is it can yellow with age 10 years plus. Look for some non yellowing silicone with anti mold agents built in. and a cauking gun.

Let the shower dry to bone dry if you can. Use a fluffy rag to soak up as much moisture as you can then let it air dry for approx 24 Hours.

I could recommend:

Sika 300ml White SikaSeal Kitchen And Bathroom Silicone Sealant - White

I/N: 1210308

$13.98

Tips masking Tape above and below the grout line you wish to fill. Cut the cauking gun nozzle at 45 degrees with approx 5mm diameter flow out of the tip. squeeze the cauking gun slow and steady while moving tip along the crack.

Have on stand by some chux like white cleaning clothes ( toilet paper at a pinch) to wipe excess silicon into the grove and form a neat round fillet wipping away any excess asap Put the tape up as soon as silicon applied as it sets in 10 mins to touch dry.

Job should last 25 years plus.

dyfuse

Thanks @EricL and @Jewelleryrescue.

Unfortunately the job is out of warranty so I am keen to look into a simple but highly effective solution.

I have read differing opinions online regarding grouting vs silicone sealing the bottom edge - it's been mentioned grout is porous and moisture may accumulate and have no where to go if sealed off by silicone. I do not know how true this is - keen to take your advice. If there are no issues with silicone sealant, happy to proceed.

Jewelleryrescue

Hi @dyfuse

Sorry the regrouters missed the mark they should have known any shower base will move and would have done a perfect job if they siliconed the flex zone before the grouting process over the rest of the wall.

So for you to use silicone is a good long term solution

It is always better to get the demolded area clean then bone dry if possible so there is no trapped moisture and the silicon bonds well with shower base and tiles.

But that will mean putting that shower area out of use for 24 hours as a minimum not always possible in a busy household.

But you can fast track this process use a regular hair drier to speed this process up or heat gun on med low is ok too but not to over heat tiles the guide is warm to touch. Keep in mind some shower bases are plastic and can melt if over heated so move the heat like paint brush strokes no one hot spot. I would heat the areas up to a warm to touch and let it cool a couple of times this process will add life span to your repair work,

Keep a roll of chux wipes handy as silicon needs to be kept tidy as possible. You can use plain vingar on tools to help smooth the final silicon bead in the corner as is resists silicon sticking to it.

EricL

Hello @dyfuse

It's true that when you apply silicone to a gap that it will prevent moisture from flowing through. This means that silicone seals against water especially silicones that are designed to be used in kitchens and bathrooms. If water or moisture needs to come out, then an outlet must be provided. But if it is necessary to seal against moisture or water flow then silicone is the way to go.

If you have any other questions we can help with, please let us know.

Eric

MikeTNZ

Hi @dyfuse,

This looks quite bad, I take it that the original contractor isn't coming back to "make good" on a job that should have lasted a lot longer than it has.

Shower areas are terrible for water ingress, now you might suspect that a lot of water damage could occur from using the shower and I struck this when

I first moved into the place where I am.

Secondary to water being splashed about during a shower, if the base of the shower tray or whatever you have has not been adequately sealed,

what you can end up with, is water moving UP the inside of the wall linings, this is called capillary action, this can go totally un-noticed.

I ended up tearing out all of the Seratone panels from my shower and replacing the timber in behind it as well, as it was all mouldy.

I think that merely sealing the cracks up, could be false economy, I really hate to say that, but you could be sealing a bigger problem in behind

them linings.

dyfuse

Thanks for your help @Jewelleryrescue, @EricL and @MikeTNZ.

Definitely sounds like a problem to resolve sooner rather than later.

So I plan to tackle this problem by:

1. Removing all the old and cracking grout and a general clean of the area

2. Ensure the gap is dried or left to dry completely out

3. Taping the area, applying silicone sealant, cleaning up the silicone bead and removing the tap

4. Leave to cure/set

EricL

Hi @dyfuse

Please keep us updated with your progress, we look forward to seeing your shower base sealed.

If you need further assistance, please let us know.

Eric

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