Can you put new moisture barrier and tiles on top of the roof terrace's old ones?

[lari]

We have a vacation apartment in Mallorca with an accompanying rooftop terrace. Now the moisture barrier under the terrace's tiled floor has started to leak, causing moisture damage to the ceiling in our hall downstairs. Since this is Spain, there is no insulation in the ceiling/floor structure separating the terrace from the apartment; it's just reinforced concrete.
To address the damage, I think there are two ways:
1) Chip away/hammer out parts of the old tiled floor and "repair" the moisture barrier, meaning make a new one on top of the old one. The result would be that we would have a different look on the floor in the repaired areas, as there is no matching tile today like the one laid 20 years ago when the house was built. This is what the insurance company wants.
2) Create a new moisture barrier on top of the entire old floor and lay new tiles on top of this. Then let the floor/ceiling dry out at its own pace before repainting the hall.

I would prefer option 2 if it would work. Then we can use non-slip tiles on the entire floor instead of the ones currently there, which become slippery as ice when wet. Are there any dangers with this approach? Or does anyone have a better suggestion?

 

[Liteavvarje]

Is there room to add another layer of tiles, considering the doors?

 

[Thomas_Blekinge]

2) Create a new moisture barrier on top of the entire old floor and lay new tiles on top of it. Then let the floor/ceiling dry out at its own pace before repainting the hallway.

That sounds like a good idea. I don't know what type of moisture barrier you're thinking of or what's common in Espana. On my terrace here in S, I have laid the same membrane used in Swedish bathrooms as a moisture barrier. Then adhesive and tiles. No water has come through the floor since then. But I can imagine that such a membrane is sensitive to irregularities in the substrate, so it might be a good idea to use self-leveling compound to ensure a proper slope.

 

[lari]

Is there space to add another layer of tiles, thinking about the doors,

in this context, it's a relatively small task to also raise the door and door frame to the corresponding height.

 

[lari]

That sounds like a good idea. I don't know what type of moisture barrier you're thinking of or what's customary in Espana. On my terrace here in S, I've used the same membrane that's used in Swedish bathrooms as a moisture barrier. Then adhesive and tiles. No water has come through the floor since then. But I can imagine that such a membrane is sensitive to irregularities in the substrate, so it might be a good idea to use self-leveling compound to get a good slope as well.

that the new moisture barrier would be watertight is not what I'm most concerned about. Rather what happens if I "encapsulate" the old tile layer, which is currently damp between the old and the new moisture barrier.

 

[Liteavvarje]

How much moisture, it's the beginning of winter in ES and maybe with rain there now, you might have to wait until summer for it to dry properly +30C, or cover it. At that temperature, the concrete dries out, it's probably not good to lay anything on something as damp as you say, it will likely detach from the surface.
When you do it, think about getting the waterproofing layer up under the door and 10 centimeters up the wall,
it usually splashes quite well from above sometimes in ES.

 

[Thomas_Blekinge]

that the new moisture barrier would stay airtight is not what I'm most concerned about. Rather, what happens if I "encapsulate" the old tile layer which is also currently damp between the old and new moisture barriers.

The old moisture barrier is probably quite damaged. Trapped water will disappear downwards within a year.

 

[Liteavvarje]

What I believe might happen if it isn’t completely dry is that the new surface might not properly adhere to the substrate. I could be slightly wrong there, but another consideration is what type of waterproofing membrane can be used. I am doubtful about using the same type as for bathrooms, as it might not withstand +50 C - +60 C that can occur when the sun is out. It probably needs to be an asphalt-like waterproofing membrane similar to a petuniummat or something that can withstand heat. I've spent many years in those latitudes but haven't seen what they use on balconies and terraces; it might be a design we're not accustomed to here in the north. It's probably worth investigating.