"Wall cancer"

Life Technology
1

I have a problem with the walls in my house. In Chinese, it’s called qiang2 bi4 ai2, which literally translated, means “wall cancer”. It means the paint on the walls bubbles up and then falls off, leaving ugly patches of bare gray concrete all over the walls.

I’ve noticed that it usually only happens on the insides of exterior walls and the other side of bathroom walls (not the side in the bathroom). I think it is probably caused by rain (or in the case of bathroom walls, water from condensed steam when taking a shower) seeping through the walls, and this water disolves salt which is in the concrete. (Concrete contains sand, and since the sand comes from beaches, it is often mixed with salt). Then the salt is pushed through the concrete, causing it to form bubbles which eventually pop off. Well, I might be wrong, but that’s my theory anyway.

And this explains why there are usually white bathroom tiles covering the outsides of most houses and buildings in Taiwan. The purpose of these tiles is to prevent rain water from seeping through the concrete, which would cause “wall cancer”. For example, there are white bathroom tiles all over the front of my house, but no bathroom tiles at all on the back of my house. And I don’t think it’s just a concidence that on the walls in my house which face the front of the house, there is no “wall cancer” at all, but there is lots of “wall cancer” on all of the walls which face the back of my house.

Anyway, my question is how to get rid of this “wall cancer”. Last summer, I scraped off all of the “wall cancer” bubbles using a putty knife, and then re-painted those walls, but less than a month later, the bubbles started coming back, and now (just nine months later), the walls look horrible again.

Is there some kind of sealant that I can put on the walls (after I’ve scraped off the paint) which will keep the “wall cancer” from coming back?

Is there any other solution, other than putting bathroom tiles all over the back of my house? (I know that would probably solve my problem, but my house is a 4-story townhouse, and the tallest ladder I could buy would only go to the middle of the 2nd floor. And it’s too much work, anyway.)

2

Fighting this myself.
Yes there is a compund available at most hardware/home stores and a lot of the “everything” stores.
Its a type of wall sealant that should be applyed to a wall you have scraped and prepped. Then you let it dry,
decide if you think one coating is enough, then paint over it.

It does seem to work…for a while. What I’ve found is that the moisture just migrates to another part
of the wall and pops out there.
Its a Taiwan thing. Good luck, maybe someone else has some helpful suggestions.

I should mention, the sealant I am referring to is for the inside walls.

3

[quote=“Mark Nagel”](Concrete contains sand, and since the sand comes from beaches, it is often mixed with salt)[/quote]If your house was made from 海砂 it would have fallen down already. Concrete is made with sharp sand, crushed rocks, for it’s internal friction. Sea sand grains are round and slide over each other. This is not to say that no houses have been built from sea sand in Taiwan, since there have been many scandals over this. I’m pretty sure the white color you see on leaky concrete is lime that’s leached out by the water.

[quote]
Is there any other solution, other than putting bathroom tiles all over the back of my house?[/quote]Yes, PU compounds that TC mentioned. If you also have cracks in the wall it’s worthwhile getting them injected with PU. The apartment I bought three years ago has only one wall exposed to the elements, and it had cancer spreading from a long crack across it. We had a guy drill holes along the crack and insert some ‘needles’ and ‘inject’ a liquid polyurethane compound into the cavities. After that had dried (two days) the needles came out and a layer of PU went on with a putty knife. I then sanded that and painted over it with regular household emulsion. Three years later, still no recurrence. :sunglasses: YMMV.

4

Ideally you need to prep both the outside and the inside of the wall. Water can also seep in through the grout between the cracks and those need to be sealed as well. B&Q has a special product called masonry lock for both indoor and outdoor applications including a special type of silicone that dries to the color of concrete. Fill in all the grout between the tiles with this and then attack the inner-wall as Hsiadogah mentioned.

It’s a real pain… :s

5

There is a kind of paint called fangshuiqi 防水漆. It’s supposed to be “water resistant”, meaning the water from outside doesn’t get through the walls. You can get it at B&Q. One problem I can see with that is, that your walls might rot from the inside without you noticing anything…

6

Maybe people here just love bathroom tiles?! Maybe you can try wallpaper for the bathrooms, perhaps protect it better?

7

I just finished scraping all of the loose paint off all of the walls that had “wall cancer”. Now the walls look even worse, but that’s just temporary, of course.

Mesheel, I don’t think “water proof paint” will make any difference because the problem is that the concrete under the paint isn’t water proof!

Hsiadogah, thanks for your very informative post about sand. Now I know that the white powder that leeches out of the walls is actually lime, not salt.

About PU: I assume that it is a thick gel like silicone, right? If I spread it over the areas of the walls where I scraped off the paint, then is it possible to spread the PU on the walls thin enough so that when I paint over it, the walls will not be bubbled up in the places where the PU is?

Also, if PU is a gel, then will paint stick to it?

I really hope that after re-painting, the walls will be so flat that no one can tell where the “wall cancer” used to be. But also I want to prevent the cancer from coming back, at least for a year or two.

8

No, PU (polyurethane) is a thick liquid, not sticky or viscous enough to call it a gel. Goes on very thin with a putty knife or similar.

9

Hsiadogah,

Thanks. I’ll try putting PU over all the areas that I scraped the paint off the walls, and then I’ll re-paint the walls. But I won’t have time for that until next weekend.

By the way, is there an English word for “wall cancer”?

Mark

10

[quote=“Mark Nagel”]
By the way, is there an English word for “wall cancer”?[/quote]Now that I think about it, this is the first time I’ve ever discussed this subject in English :blush:
Rising damp? (not the sitcom) I don’t know, I’ll ask a friend who’s a civil engineer.

11

Probably tiles wouldn’t solve the problem; after the recent rain I als experienced “wall cancer” (and some fungus to go with it), even where the outer walls are covered with tiles.
Maybe it’s coincidence that it occurs where you have no tiles, i.e. the non-tiled side maybe the one that is more exposed to the elements (rain etc.).

12

Okay guys. Here it is. The wall needs to be completely scraped, cleaned and then sealed with a sealer. Like Drylok(which will actually seal the concrete and not just cover it). It can be bought at B&Q(pricey though)(available in latex or oil base). Not a water resistant paint or such. The wall needs to be cleaned with a proper solvent as well(a drylok brand will do well). Problem here is that the water will just move to another wall and come out there. If you seal all the insides of all the exterior walls then maybe you have a chance, but then it might come up through the floors.

PU is a thick liquid and not by anymeans thin. It goes on easy on a flat horizontal surface but is a major pain on vertical ones. It is not meant to be put on with a putty knife. It is not really a sealer. It is not pourous enough nor thin enough to actually get into the concrete. PU is a cover to be put on top of concrete, eg. flat roofs or floors(garage,etc.) to prevent water from penetrating. Any cracks or thin areas will let water in and it will just bubble. You can use it in conjuction with a waterproof glue though, which is thin and will penetrate the concrete. DO NOT use PU in a few spots and not the whole wall. This will just mean the water will flow to another spot and the whole thing will start all over again and you just waisted your time.

Concrete is not waterproof and neither is the grout between the tiles. The tiles, once the initial surface wears off, become pourous as well. You can but should not seal both sides of a wall. This will trap things in the wall itself and cause problems later. Unless of course you are building a new house and everything is dry and sealed well to begin with.

If you wish to seal it properly then seal the outside if possible. This means using silicone to seal the grout between every tile and sealing the tile itself once again. The amount of exposure it has to the elements will directly reflect how long this seal will last. There is a paintable compound here but I am not sure how to write it. It can be applied to the exterior wall using a roller(over tile and grout). It will last approximately 5+ years. All forms of sealant will have to be reapplied to the walls on a regular basis here in Taiwan due to the weather and constant humidity.

Yes, many houses here have been built using sea sand. This is a major problem. If it is old then there is a good chance that it is one of those houses. Other than that the houses here use river sand. It could also be lime coming out but not as likely here. The amount of lime used here in the concrete is low, not like back home, so if it leeks out then the whole structure is in danger of collapse(weakened concrete). Lime gives concrete it’s strength.

You could also put a metal or other wall onto the existing exterior wall(on the outside that is). This would be the best but also very costly.

After sealing the outside and then letting the wall completely dry you should be able to just scape, clean and then paint with a regular latex paint. This should then last a lot longer. No guarantees here in Taiwan though.

Final conclusion. If you rent, just cover it and live with it. If you own, then decide on a budget and seal it as best you can on that budget. Or, go for broke and do it properly.

Tiles do not solve the problem, they only delay it. The roof must also be sealed to make sure that the water is not coming in from there. Water will find the path of least resistance and come out wherever is weakest.

As for your house only being tiled on one side. It has nothing to do with exposure to the weather. It is simply the area that is seen most(usually the front) and will make it look the best for selling that is tiled. The other is not tiled due to cost. Tile costs money and the builders here want to make as much as possible. They sell to the uneducated public and get away with it. They do not seal the concrete before tiling either as that too costs money. In Taiwan it really is BUYER BEWARE!

If any questions then let us all know or pm me and I will talk at you. Bye the way, civil engineers deal with the layout of places(cities etc.) and not the building of them. You need a construction/structural engineer for this info., and believe me some of them don’t even know.

13

Surf,

Wow, what an informative post! You seem to be an expert!

But now I realize that it would be a heck of a lot of work to get rid of the “cancer”. My wife and I do own the house, but now I wish we were renting because then we could ask the landlord to do the work!

After reading your post and realizing how difficult it would be to completely get rid of the “wall cancer”, I think what I’ll do is just paint over where all the bubbles used to be (I’ve already scraped off all of the bubbles last weekend), and then every few months, I’ll re-scrape and re-paint. That would be a lot easier and it should look good for at least one or two months before the bubbles come back, depending on how often it rains.

Also, I’m glad you told me that if I put PU (or any other sealant) only on the places that were bubbled up instead of putting it on the whole wall, then the “cancer” would just re-appear in different places. So I’m glad that you’ve saved me a lot of wasted time.

Thanks a lot for your help.

Mark

14

Hey, no problem. If you want about a year of an okay paint job(and sometimes more) scape the whole wall and use Drylok (latex or oil)(latex doesn’t stink like oil so I prefer it). Also, latex is better for concrete(it absorbs better). Try to do this on a fairly dry wall. I would wait until after a week or so of dry weather before doing this though. If too wet it will all peel, no matter what you do. And very quickly at that. Then paint over it or just leave it as is. It is in a couple of colours and then if a problem just do touch up on that. That is what I have done with the house I rent and it cuts down on the work. It does not cure the problem but it will make for a little bit more of a rest time. It will also then take a while for the water to find a new outlet and then you Drylok that place. If I can get the name of the other waterproofer here in Taiwan I will get it off to you. I am not an expert per say, I don’t think, but thanks for the complement. I do own a construction company and my family has been in the business for years. I guess that has given me a little knowledge.

The weather here should get better soon and maybe it would be best to just look at an ugly wall for awhile and then do a better job later on than a short quick fix now that you will only get frustrated with many times over. That is what happens to me so I know the feeling. I have to redo a wall here too so I am just waiting for now. IT’S NOT UGLY, IT’S ART DECO!! Good luck and pm me if you have any questions I might be able to help out with.

15

Hey, haven’t heard an update on the wall cancer in a while. How did the wall cancer treatment work out? Did you get the problem fixed? What method did you use? How much time did you put in? Many more questions. Let us know how it went.

16

Here’s the update: I tried to scrape all the paint off the whole wall, but I couldn’t get the paint to come off except where the “wall cancer” was, so that’s all I ended up scraping off. Then I re-painted over only the areas that I scraped.

It hasn’t started to bubble up yet, but it’s only been a few weeks, and I’m sure it will bubble up eventually, especially during the typhoon season (July to September).

I regret that I didn’t re-paint the whole wall because new paint is a slightly different shade from the old paint. But since I’m probably going to have to re-scrape and re-paint just a few months later, I might as well wait until then to re-paint the whole wall.

17

[quote=“Mark Nagel”]Here’s the update: I tried to scrape all the paint off the whole wall, but I couldn’t get the paint to come off except where the “wall cancer” was, so that’s all I ended up scraping off. Then I re-painted over only the areas that I scraped.

It hasn’t started to bubble up yet, but it’s only been a few weeks, and I’m sure it will bubble up eventually, especially during the typhoon season (July to September).

I regret that I didn’t re-paint the whole wall because new paint is a slightly different shade from the old paint. But since I’m probably going to have to re-scrape and re-paint just a few months later, I might as well wait until then to re-paint the whole wall.[/quote]

you may look into TRICOLASTIC made by Grace Construction Products, a german firm. the walls of our bathroom corner shower stall is simply a continuation of the original tile pattern used in the bathroom, to prepare the walls for twice+ daily showers, we mixed tricolastic with cement and completely coated the underlying cement walls with a layer of tricolastic(when properly mixed it is a thin grey liquid)

works like a charm, and can be used for building exteriors as well, simply brush an even layer over tiles, cement etc.

as surfbunny mentioned, you must cover the ENTIRE area, not simply the spot where the water/wall cancer is apparantly leaking from, because water, as a liquid will find the path with least resistance and if its blocked off at point A, it will migrate to B, C, and D if not treated in a similar fashion

TRICOLASTIC - miracle stuff, we found the local distributer at a construction goods show at TWTC over 10 years ago, i dunno if they’re still around though

18

[quote=“mungacious”]

as surfbunny mentioned, you must cover the ENTIRE area,

TRICOLASTIC - miracle stuff, we found the local distributer at a construction goods show at TWTC over 10 years ago, i dunno if they’re still around though[/quote]

Has anybody stripped tiles off the outside of a house. Ar they water traps in cracks or do they form an impervious layer.

19

[quote=“Ironman”][quote=“mungacious”]

as surfbunny mentioned, you must cover the ENTIRE area,

TRICOLASTIC - miracle stuff, we found the local distributer at a construction goods show at TWTC over 10 years ago, i dunno if they’re still around though[/quote]

Has anybody stripped tiles off the outside of a house. Ar they water traps in cracks or do they form an impervious layer.[/quote]

cement and nearly every other exterior construction material alone are porous. while the surface of kiln finished exterior tiles may be waterproof to some extent, the gaps between the tiles are almost never waterproof and this is where the ‘wall cancer’ precipitates from. cover your ass and use a nice layer of PU/tricolastic over the ENTIRE surface, not just the gaps, not just the tiles, cover everything. even better if you’re in the process of re-tiling the whole surface, treat the underlying cement with a layer first, align and lay ur tiles, hit that new tiled surface with another layer of PU/tricolastic.

if you cover an entire wall, the water will eventually find another hole to come out of…this is unavoidable…perhaps you could seal the whole house in a cling-wrap or hermetically seal everything(including upstairs neighbor’s leaking water fixtures) with red wax…jk

20

Something like a house as we knew it before coming to Asia with damp course beneath the house, insulation and sloping roof with extended eaves to protect the walls that are themselves waterproof.

We own 1/4 of a house. Upstairs 2 floors. Its going to be hard to work out what we can water proof. Neighbours would be rightly pissed if we put half a roof on and 1/4 of the walls became waterproofed if it changed the tile color.