Advice needed on balcony waterproofing—new damp spot appeared

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Nickster

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Hi everyone, hoping for some advice.

We had our balcony waterproofed with a torch-on membrane and then tiled over. After the first rains, we noticed a big damp spot on the ceiling below the balcony. The contractor came out, removed two tiles, and found that the tiling had damaged the torch-on membrane in that area. He repaired the torch-on, and after some heavy rains, that original ceiling damp spot hasn’t come back—so that part seems sorted.

However, while the tiles were still off, water pooled in those two spots where the torch-on was exposed, and we noticed another damp patch forming elsewhere.

The contractor has since re-tiled those areas, but with recent rain, we’re now seeing a new, small damp spot on the wall beneath the balcony.

The contractor’s suggestion is to apply Sika sealant where the grout of tiles would be and remove grout to try seal any minor leaks, since this new spot is quite small. But I’m worried there might still be a compromised or exposed part of the torch-on membrane underneath the tiles causing this new leak.

Has anyone dealt with something similar? Is sealant a good solution for small leaks, or should we rather lift tiles again to check the torch-on layer properly? Any advice would be appreciated!
 
Was the contractor not able to do what he suggested?

I am aware that many contractors don't touch waterproofing issues. It's sometimes just too big a problem that won't go away easily.
 
Get a contractor who is a Waterproofing specialist.
 
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@Nickster

no need to remove the tiles or grout, you can seal the whole area, the water is penetrating through the grout... so whoever did your grouting didn't do it correctly, as a mention you can't use water when mixing waterproof grout... anyway too late for that now. I do love how the contractor blames the tiling damaging the membrane, I would have asked him, "how did the water get to the membrane in the first place?"

just have a look at TFC products at the hardware store, they are expensive. They make a whole bunch of different sealers.. I would find one that best suits your needs and then paint on about 3 coats.


TFC - Grout Seal
TFC Sealer Cement | Agrimark
TFC - Invisible Sealer 1L
TFC Smart Seal 1L - Habitat Potch
 
First time I heard about tiling over a torch on membrane.

Its for a roof, and you need to do a topup paint every 3 to 5 years. The paint is silver and turn grey in the sun.

Would this not be a better solution?
IMG_20250706_235417_044.jpg

Also is the slope of the balcony correct? Was a waterproofing grout used?
IMG_20250706_235431_500.jpg
IMG_20250706_235426_093.jpg
 
I would highly recommend NOT TO TILE over a torch on membrane. I hope they didn't tile directly onto the membrane and they used a substrate compatible with tiling, however if your contractor pulled some tiles to find an issue everything is already compromised.

You need PVC sheeting or similar between the screed and the membrane. You will need a really thick layer of screed/mortar (45 to 70mm) or compatible substrate recommended by the membrane manufacturer + a flexible adhesive for the tiles. Even then there is a massive risk. The membrane manufacturer specification will probably say something like "this product is not suitable for tiling".

The fact that the contractor already discovered the membrane was damaged it is guaranteed to have bigger issues. I would definitely get an approved waterproofing and roofing specialist to come see what is going on there.

The membrane should also be properly applied in the corners and upstand and down the drain outlets.

Anything you do to try fix it now is only going to be temporary and there are just too many variables to give advice here.


1000054584.png1000054586.png
 
Last edited:
Wrath of Khan MD said:
@Nickster

no need to remove the tiles or grout, you can seal the whole area, the water is penetrating through the grout... so whoever did your grouting didn't do it correctly, as a mention you can't use water when mixing waterproof grout... anyway too late for that now. I do love how the contractor blames the tiling damaging the membrane, I would have asked him, "how did the water get to the membrane in the first place?"

just have a look at TFC products at the hardware store, they are expensive. They make a whole bunch of different sealers.. I would find one that best suits your needs and then paint on about 3 coats.


TFC - Grout Seal
TFC Sealer Cement | Agrimark
TFC - Invisible Sealer 1L
TFC Smart Seal 1L - Habitat Potch
Click to expand...
No amount of sealant over the tiles is going to stop the water.

The only way to fix this is to remove all the tiles and do it correctly.
 
Last edited:
To clarify, the contractor is a waterproofer who followed a standard approach for tiling over a torch-on bituminous waterproofing membrane, which involves applying a screed layer over the membrane and then using a flexible adhesive to fix the tiles. The membrane itself is a thermoplastic material, so it requires careful handling during the tiling process to prevent damage.

Unfortunately, during the tiling, it appears that the contractor inadvertently damaged a section of the membrane, which likely compromised its integrity and contributed to the damp spot. Additionally, I’m concerned that the faint mark in another area could indicate similar issues.

I’ve consulted with another waterproofer who suggested that the only way to be certain is to remove everything and redo the job. However, given that it’s winter, and considering the additional costs, I’m hesitant to go down that route just yet. This contractor also worked on our other balcony, which has shown no issues, but I am getting frustrated with the ongoing uncertainty and the inability to close this chapter.
RedViking said:
I would highly recommend NOT TO TILE over a torch on membrane. I hope they didn't tile directly onto the membrane and they used a substrate compatible with tiling, however if your contractor pulled some tiles to find an issue everything is already compromised.

You need PVC sheeting or similar between the screed and the membrane. You will need a really thick layer of screed/mortar (45 to 70mm) or compatible substrate recommended by the membrane manufacturer + a flexible adhesive for the tiles. Even then there is a massive risk. The membrane manufacturer specification will probably say something like "this product is not suitable for tiling".

The fact that the contractor already discovered the membrane was damaged it is guaranteed to have bigger issues. I would definitely get an approved waterproofing and roofing specialist to come see what is going on there.

The membrane should also be properly applied in the corners and upstand and down the drain outlets.

Anything you do to try fix it now is only going to be temporary and there are just too many variables to give advice here.


View attachment 1832878View attachment 1832880
Click to expand...
 
Nickster said:
Hi everyone, hoping for some advice.

We had our balcony waterproofed with a torch-on membrane and then tiled over. After the first rains, we noticed a big damp spot on the ceiling below the balcony. The contractor came out, removed two tiles, and found that the tiling had damaged the torch-on membrane in that area. He repaired the torch-on, and after some heavy rains, that original ceiling damp spot hasn’t come back—so that part seems sorted.

However, while the tiles were still off, water pooled in those two spots where the torch-on was exposed, and we noticed another damp patch forming elsewhere.

The contractor has since re-tiled those areas, but with recent rain, we’re now seeing a new, small damp spot on the wall beneath the balcony.

The contractor’s suggestion is to apply Sika sealant where the grout of tiles would be and remove grout to try seal any minor leaks, since this new spot is quite small. But I’m worried there might still be a compromised or exposed part of the torch-on membrane underneath the tiles causing this new leak.

Has anyone dealt with something similar? Is sealant a good solution for small leaks, or should we rather lift tiles again to check the torch-on layer properly? Any advice would be appreciated!
Click to expand...
I could never get my balcony right after many waterproofing attempts so ended up installing an awning with side panels.
 
Nickster said:
To clarify, the contractor is a waterproofer who followed a standard approach for tiling over a torch-on bituminous waterproofing membrane, which involves applying a screed layer over the membrane and then using a flexible adhesive to fix the tiles. The membrane itself is a thermoplastic material, so it requires careful handling during the tiling process to prevent damage.

Unfortunately, during the tiling, it appears that the contractor inadvertently damaged a section of the membrane, which likely compromised its integrity and contributed to the damp spot. Additionally, I’m concerned that the faint mark in another area could indicate similar issues.

I’ve consulted with another waterproofer who suggested that the only way to be certain is to remove everything and redo the job. However, given that it’s winter, and considering the additional costs, I’m hesitant to go down that route just yet. This contractor also worked on our other balcony, which has shown no issues, but I am getting frustrated with the ongoing uncertainty and the inability to close this chapter.
Click to expand...
Great! Contractor will then have to pay to completely redo it! Get a second opinion. Next time tell him to put a protective layer between the torch on and the screed/mortar! But make sure he is liable for all costs.
 
RedViking said:
Great! Contractor will then have to pay to completely redo it! Get a second opinion. Next time tell him to put a protective layer between the torch on and the screed/mortar! But make sure he is liable for all costs.
Click to expand...
Yeah this is what I suspect, but eish getting this done without a fight who knows. Also, the cost of litigation if it goes that route is simply not worth it with the cost of legal fees v the job. Might as well pay for someone to redo it as it will save me the headache and cost.
 
Nickster said:
Yeah this is what I suspect, but eish getting this done without a fight who knows. Also, the cost of litigation if it goes that route is simply not worth it with the cost of legal fees v the job. Might as well pay for someone to redo it as it will save me the headache and cost.
Click to expand...
He wants to do a less evasive approach. If it doesn't work, I will insist on opening up again. The balcony is quite big and it's just this minor spot, so I am trying to be reasonable here. The issue with getting someone else is they will just want to redo it which is understandable.
 
Nickster said:
Yeah this is what I suspect, but eish getting this done without a fight who knows. Also, the cost of litigation if it goes that route is simply not worth it with the cost of legal fees v the job. Might as well pay for someone to redo it as it will save me the headache and cost.
Click to expand...
Could do small claims if it is not a massive job. But if he is a professional and have an issue with doing it correctly you can report him. If it was me I would redo it for my client. Not sure what is up with this country and the building industry and people not taking responsibility for their work
 
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It appears as though the contractor damaged it? Good luck trying to get him to admit it.
 
RedViking said:
Could do small claims if it is not a massive job. But if he is a professional and have an issue with doing it correctly you can report him. If it was me I would redo it for my client. Not sure what is up with this country and the building industry and people not taking responsibility for their work
Click to expand...
Yeah, agreed. Look, he’s a nice guy, so let’s see where we land. It’s above the SCC threshold, and despite being an attorney, I wouldn’t litigate my own matter. I do litigation (nothing in mag court), and it’s just not worth the cost of hiring an attorney or advocate, drafting papers, waiting for a trial date, etc. The costs recoverable are usually only about 20% of legal fees, so it’s probably more cost-effective to bring in someone else if he doesn’t come to the table.

I mean, he did a great job on the other balcony, so I can’t see why he can’t get this one right.
 
I have much the same woes, except I inherited the issue. Wish I had a contractor to blame LOL.
 
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