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What to grout and seal my outdoor tiles?

Hi!

I’ve recently tiled my rooftop terrace (outdoors, obviously), and noticed that rainwater had gotten stuck under them and was dripping into the rooms below. While I’ve tackled the problem of this stuck water separately, I want to ensure that more rainwater doesn’t seep through the tiles again.

I realized that the low-quality grout we had used was not water resistant, nor had a waterproof sealer been used. I’m now planning on removing this grout, and replacing it with something more resistant, as well as using a sealant to prevent further leaks.

Does anyone have any recommendations for suitable outdoor grout products, as well as a sealer I could use for them? This house is overseas and subject to the monsoon period, so rain is pretty uncommon, except quite intensely for a few months of the year.

Any help at all would be appreciated, as well as other tips to help waterproof the roof tiles further.

Thanks!

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Comments

Jewelleryrescue

Tiles are pretty much used for decoration there ideally should have being a waterproofing membrain under the tile glue bed and you will never think twice about a leakage.

So the best option is to take the tiles off and apply a water proof membrain before retiling. for a great long term solution for the life of the house.

But with tiles allready down the best grout is epoxy grout its not cheap but if installed correctly may solve your water problem with out having to seal any thing unless your tiles are porous ? Then your will need a high quality sealer from the nu tech range of water based out door sealers I trust to do the job.

You could also epoxy over the whole tiles and seal them that way as an extreme measure and the epoxy is UV resistant not 100% proof so best to shade it.

JacobZ

Hi @anshul,

A warm welcome to the Bunnings Workshop community and thank you for your question.

Generally, in outdoor applications, a rubberised waterproofing membrane is applied beneath the tiles to protect the substrate, whether it is concrete, fibre cement sheeting or timber.

Grout is not waterproof, which is a common misconception in tiling. Grout is designed to fill the gaps between tiles and provide a smooth, finished surface, but it is inherently porous. This means it can absorb water, particularly if it is unsealed. Over time, moisture can penetrate the grout, potentially reaching the substrate underneath the tiles, which can lead to problems.

Grout sealers are designed to make cleaning and maintenance of your grout easier, not to make them waterproof. They will make your grout somewhat hydrophobic, but not truly waterproof. You can use a grout sealer like this Dunlop Grout Sealer to add some protection to the grout, but it will not make it waterproof.

If you want to stop the water from dripping through completely, you'll need to remove the tiles and waterproof the rooftop terrace. This will involve applying an exterior-grade waterproofing membrane and accessories, such as wall flashings and drains, that are relevant to your circumstances.

Let me know if you have any further questions.

Jacob

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