We have a flat rooftop terrace on the backside of our home. The grout between the tile and the metal bottom strip is eroding away and creating some minor leaks in the attic below the terrace.

Terrace is completely exposed to conditions (sun majority of day and no roof to shield it so any rain it sees a lot of water during storms).

The expense of caulk, ease of use and or how it looks are zero factor here. The only thing I care about is finding something that is going to give us the best seal and prevent leaks.

Ive seen a lot of different exterior caulk/sealant options and it's a little overwhelming. Given my scenario what product would y'all say is my best option?

There is an ice and water shield and a few other layers beneath the tile for the water proofing. The walls also have ice and water shields and wrapped as well as the metal capping you see you in the pics

The minor leaks are occurring only on the side in the pics. The grout has only eroded in the exact spot the leaks are occurring in the attic below so I'm not sure if there could be other entry points or that's just a coincidence.

How does the water leave that area?

Looks like the missing grout is a symptom of the leak and not the cause but I could be completely wrong.

There are 3 scuppers to the left of the first picture. Support Beams were stripped/slopped where water will naturally run off. The leak only occurs on extreme storms with heavy winds where water pools on that one side

Sika is good stuff so is Dap

Probably not what you want to hear, but if it was me, I'd scoot around on a nice day and remove all of that grout& replace it with a good exterior caulk. That "change of plane" will probably always be a problem in your situation. This article has some good information.

https://floorelf.com/caulk-or-grout-in-corners

NP1 urethane caulk will work well here. Stretches up to 30% of original size to eliminate the gaps where your original caulk failed due to movement apparently.

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original caulk failed due to movement apparently

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I think OP said it was grout.

schwack schwack said:

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Quote:

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original caulk failed due to movement apparently

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I think OP said it was grout.

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My apologies, I saw the white caulk at the top of 2nd pic and thought that to be the problem.

The dust on my screen obscured the missing grout. Clean screen.

Seeing the extent of the grout failure, it appears all of the grout seams need to be cut out and a better grout (maybe one more suitable for conditions?) applied.

The NP1 would serve well as a seal around the outer edge of the tile to flashing.

No apology necessary!

I would use NP1. I don't know how it's leaking if it's been sealed and the coping is done properly. There is no way to know without photos or tearing off and that kinda sucks.

The NP1 or GeoCel will stick and never come off but I cannot speak to the long term effectiveness in the particular application.

If cost is not an issue, then I'd probably investigate why it's leaking. Caulking really shouldn't be used as a primary means of preventing leaks in many cases. It's like relying on caulking in a shower pan.

Is this the product y'all recommend?

Looks like there are several different types so want to make sure buying correct one


2 Pack MasterSeal NP1 White Polyurethane Caulk https://a.co/d/1NMmlK5

Yes but McCoy's hardware carry's it as well if you have one nearby. May be a bit cheaper from them.

Jason_InfinityRoofer said:

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I would use NP1. I don't know how it's leaking if it's been sealed and the coping is done properly. There is no way to know without photos or tearing off and that kinda sucks.

The NP1 or GeoCel will stick and never come off but I cannot speak to the long term effectiveness in the particular application.

If cost is not an issue, then I'd probably investigate why it's leaking. Caulking really shouldn't be used as a primary means of preventing leaks in many cases. It's like relying on caulking in a shower pan.

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Know of any roofer recommendations who could maybe come investigate to try and find issue on a flat roof? In Houston

bullard21k said:

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Is this the product y'all recommend?

Looks like there are several different types so want to make sure buying correct one


2 Pack MasterSeal NP1 White Polyurethane Caulk https://a.co/d/1NMmlK5

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Yes, that's the stuff, but it can be found cheaper locally. That price looks high by at least 50%.

bullard21k said:

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Jason_InfinityRoofer said:

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I would use NP1. I don't know how it's leaking if it's been sealed and the coping is done properly. There is no way to know without photos or tearing off and that kinda sucks.

The NP1 or GeoCel will stick and never come off but I cannot speak to the long term effectiveness in the particular application.

If cost is not an issue, then I'd probably investigate why it's leaking. Caulking really shouldn't be used as a primary means of preventing leaks in many cases. It's like relying on caulking in a shower pan.

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Know of any roofer recommendations who could maybe come investigate to try and find issue on a flat roof? In Houston

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Sorry for not getting back sooner. I wanted show the photos to my GM and some of my other project managers. We all seem to agree that you are probably on the right track for now. While I still don't think the caulk is a long term permanent fix, it very well could be the only thing and the way it was put together. I think, for the cost of the caulking, you should give that a try first. You should be able to let that cure and leak test that easily with a water hose or a bucket of water. We would typically do the underlayment portion of that, but we don't do tile, so I was trying to figure out if you needed a roofer or a shower remodeler since that is essentially a giant shower pan. It may be constructed similarly. I will reach out to another colleague of mine at HARC and see if he can point you in the right direction.

Be advised that a leak like this is likely going to require a fair bit of tear off around the perimeter at a minimum to identify how it was put together and where/if it is not done properly. How old is this roof? It looks pretty new. Is it under warranty by your builder/installer by any chance?

EDIT TO ADD: You can shoot me an email (in my profile), and I can get you in touch with a friend of mine who specializes in this type of work. That way, you have the contact in case you opt to go further. He also confirmed that it will likely require a complete tear off down to the decking for a true long term fix. So, just a heads up on that.

Did yall build or buy an existing home? Pictures of the construction would obviously help here. It should be built like Jason noted as a bathtub with an AWB sheet good or fluid applied under the entire tiled surface and wrapped up the walls to under the parapet caps and only open at the scuppers, but obviously that isn't the case since you're experiencing some leaking.

Aggietaco said:

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Did yall build or buy an existing home? Pictures of the construction would obviously help here. It should be built like Jason noted as a bathtub with an AWB sheet good or fluid applied under the entire tiled surface and wrapped up the walls to under the parapet caps and only open at the scuppers, but obviously that isn't the case since you're experiencing some leaking.

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I built. I don't have a ton of great pics but I'll post what I can find.

The pic with door on the ground I believe is the asphalt type material that was down before we put the new tile down.

The texrite was then put down and graded to slope the water towards the scuppers but I'm not sure if the asphalt material was pulled out before that was done.

I can't find pictures of when the original framing was done before the asphalt material was complete. The parapet wall is all stucco so whatever was done prior to the stucco going up I'm not entirely sure other than I know an ice and water shield was wrapped under everything. If they did it correctly I'm not positive

I'm thinking of getting Texrite Flowrite and putting it on top of a low spot in my driveway. Can I get it at HD or Lowe's

i've watched enough mike holmes shows to feel confident enough saying you have a bigger problem here. grout would never have been a waterproofing barrier, so something underneath isn't right.

sts7049 said:

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i've watched enough mike holmes shows to feel confident enough saying you have a bigger problem here. grout would never have been a waterproofing barrier, so something underneath isn't right.

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Absolutely. Grout is porous, and is not waterproof nor is it intended to be. Yes, missing grout will allow water in more easily than having to pass through the grout. But the grout is not the problem. The problem is the water proof barrier under it has failed.

As others have said, this likely isn't a grout issue. There should be some kind of membrane barrier or flashing that goes under the tile and up the wall. You should have a waterproof membrane under the tile that turns up into the wall underneath that metal. It should form a bowl for the roof.

My guess is that the grout failed, pieces were pushed into this membrane, and punctured it. When the grout was installed, it was just pushed into the gap between the metal, the tile, and everything supporting the two. There's likely space behind it, and chips or chunks got back there and damaged the waterproofing underneath it all.


This is probably not exactly what you have, but good information for how this should be constructed in general.
https://www.buildingscience.com/documents/insights/bsi-051-decks-roofs-you-can-walk-on

This is a good detail that should be similar to what you have.

Great pictures - definitely helps explain the construction.

So the asphalt product that was down was just a modified bitumen roofing product, perfectly suitable for the area but something that would be replaced every so often akin to asphalt shingles.

Looks like the mortar bed was installed directly on top of the roofing, since some of it is still visible at the door sill in one of your images.

Then tile installed on top of the mortar bed, and since the level of tile was above the bottom of your wall sill flashing, the tile was just grouted or caulked to the flashing.

So what is happening now, assuming the water you found in the attic is coming from this patio, is that water is getting below the tile surface, presumably down to the asphalt roofing and it has found an exit point other than the original scuppers. Either the bitumen roofing has a puncture, has degraded, or doesnt play well chemically with the mortar bed.

Temporary fix for most of the water is the caulk like you are asking about, but grout and mortar aren't water proof, so water will still get below the tile surface and potentially where you don't want it.

Permanent fix involves removing tile, waterproofing the area with a new fluid applied or sheet good, and reinstalling tile.

Sealant appears to be in a good shape.

As others have said, this is likely a waterproofing issue.

I cannot comment much further, but the pictures help a lot. I have never installed a roof in this manner. That's not to say it's wrong, that's just to say I am not experienced in the products and techniques required for this application.

I am not sure that modified bitumen product used here is suitable for the application. I also don't think it 'won't work'. It could, and probably should. If it is accepted by the manufacturer, I would at least think it needs to have a base sheet beneath it as if you were building a 'flat roof'. Then you would have your cap sheet, which is what is in your photo. There are minimum overlaps required. If your roof has a slope of any amount, this should be suitable provided the base sheet was underlaid properly to flashings. I an relatively confident that your issue is constrained to the perimeter. Therefore, you may be able to pull enough tile to make an educated corrective adjustment with a waterproofing product such as ice & water shield or similar product.

Water will get through the grout and water will be between the mortar and the mod-bit sheet. It will leave via transport and evaporation. Therefore, whatever you do must be able to contain the water until that takes place.

It may not be quite right, but I don't think it's the end of the world.

That Texrite Flowrite 250, according to the text on the bag, is for interior use only.

That may or may not be causing an issue but it struck me as odd.

Aggietaco said:

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Great pictures - definitely helps explain the construction.

So the asphalt product that was down was just a modified bitumen roofing product, perfectly suitable for the area but something that would be replaced every so often akin to asphalt shingles.

Looks like the mortar bed was installed directly on top of the roofing, since some of it is still visible at the door sill in one of your images.

Then tile installed on top of the mortar bed, and since the level of tile was above the bottom of your wall sill flashing, the tile was just grouted or caulked to the flashing.

So what is happening now, assuming the water you found in the attic is coming from this patio, is that water is getting below the tile surface, presumably down to the asphalt roofing and it has found an exit point other than the original scuppers. Either the bitumen roofing has a puncture, has degraded, or doesnt play well chemically with the mortar bed.

Temporary fix for most of the water is the caulk like you are asking about, but grout and mortar aren't water proof, so water will still get below the tile surface and potentially where you don't want it.

Permanent fix involves removing tile, waterproofing the area with a new fluid applied or sheet good, and reinstalling tile.

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Is it even possible to reuse the tile if we opt for the permanent fix solution and pull it up and water proof in your opinion?

Jason_InfinityRoofer said:

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I cannot comment much further, but the pictures help a lot. I have never installed a roof in this manner. That's not to say it's wrong, that's just to say I am not experienced in the products and techniques required for this application.

I am not sure that modified bitumen product used here is suitable for the application. I also don't think it 'won't work'. It could, and probably should. If it is accepted by the manufacturer, I would at least think it needs to have a base sheet beneath it as if you were building a 'flat roof'. Then you would have your cap sheet, which is what is in your photo. There are minimum overlaps required. If your roof has a slope of any amount, this should be suitable provided the base sheet was underlaid properly to flashings. I an relatively confident that your issue is constrained to the perimeter. Therefore, you may be able to pull enough tile to make an educated corrective adjustment with a waterproofing product such as ice & water shield or similar product.

Water will get through the grout and water will be between the mortar and the mod-bit sheet. It will leave via transport and evaporation. Therefore, whatever you do must be able to contain the water until that takes place.

It may not be quite right, but I don't think it's the end of the world.

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In your opinion should I go ahead and calk to band aid for now?

Or should I wait until I get a roofing expert like your recommendation out here to view the work before calking?

Unfortunately not. The tile was put down with thinset mortar or some type of tile adhesive. Won't be possible to remove the tiles in a reusable fashion if that's the route you take.

Anything you can do to slow the ingress of water, or stop it, is advisable in my opinion because it's your home. However, it might also make it hard to diagnose if anyone wants to leak test it. Use your judgement.

I encourage getting a few folks to look at it. You won't be hurting anyone's feelings if you don't use my referral and I wouldn't know anyway. I encourage it for this situation. We are all professionals but we also all have different experiences to bring to the table when diagnosing things. No stupid questions. If something doesn't sound right, ask for clarification.

I also agree with the poster above that the odds of salvaging the tile are low. You may be able to heat it and pull it up with the modbit though. I'm not sure. I'd prepare for the possibility of them being damaged. It's entirely possible and maybe likely that removing the edge tiles will damage the underlayment and it ends up as a full tear off. If that happens and you can yank the tiles off with the underlayment, then you may be able to save the tiles. There are a lot of unknowns but either way, the leak is fixable.

Tile could be salvageable - if your installer did a crappy job (no offense here, just a lot of crappy tilers out there). You could find that you can pop those loose if thin set adhesion was poor or not buttered correctly. Even in that case, the chance you could pull them all without damage is pretty slim.

If it were me, I would caulk the perimeter for the time being and start planning on how to make a permanent fix.

ETA: this is all assuming that the source of your attic leak is from this flooring area. Like Jason noted, you could employ your SO, kid, neighbor, etc. to help you leak test just to try and better identify.

Thanks for all the help guys. I think I'm going to proceed with getting NP1 applied and get professional over as quickly as possibly to review case.

With guys that have used this stuff….

It's supposed to rain Saturday but i have some free time to apply the whole thing Friday mid day. Is that enough time to sufficiently dry/cure?

https://assets.master-builders-solutions.com/en-us/masterseal-np-1-tds.pdf