Hi all, need your help in identifying what is wrong with my wall. During reno, my contractor said he helped me applied some waterproofing solution to this wall under my study table (the exterior wall is directly exposed to the elements) without consulting me. At the time, whatever they applied to the wall, it stained the wall in bright yellow greenish and brown colour. Didn't think much of it as I thought it would be painted over.

However now we are in rectification phase, and they have spent hours of manpower scraping and painting over the wall and within hours the stain will just come back. It's very frustrating and the keep saying they will solve it but I'm wondering if anyone has any idea what's going on or ideas to solve? Thank you.


1.Before reno, the wall had issues.

2. After application of the unknown solution during reno.


3. Current situation, after multiple attempts to paint it over.


++Update++

Updated with pictures of wall from the other side.

The black floor tiles were added in by my contractor as a sort of barrier from the soil and grass as the wall used to terminate right at the grass.




This post has been edited by kimberlycun: Oct 10 2024, 11:54 AM

Mine having this issue as well. I suspect it was my wall pillar crack and rain water seeping through them.

Definitely still have water seeping into the wall. Pretty dangerous as it is close to the outlets as well.

Need to identify the source of water.

Experienced this from second floor toilet having water seeped downwards to first floor ceiling.

This post has been edited by jiangchen: Oct 10 2024, 09:30 AM

Mine also....
Confirm water leaking....

This looks like prolonged water seepage through the cement wall/pillar. you will need multiple coats to cover the mark. or paint a layer of sealers.

Have this kind of issue at my porch wall also. If paint sealer without rectify the crack, can be solved?

Take a picture from the outside showing the opposite side of the wall with your lawn

As long as the source of water is not identified, I don't think it can be solved.

The water will just find areas that are not sealed well to go to.

Water seeping. Could be from the window frame edges.

Any pipes nearby actually?

apply waterproofing on the other side, this can happen if no damp proof membrane is laid below the brickwall also.

walls cements bricks becomes porous through age, if you dont find the source and fix it, you basically creating a bin with sealer at the floor wall and it will soon peel or give way. worst it will seep to the floor tiles. water always find its way.

Does the wall feel damp? If it is, you'll need to solve the moisturiser problem first

The house was unoccupied for 10 years so could be it. From the outside (picture updated in OP), wall looks ok? Just wondering if there's still fresh leakage or from years of seepage.

Not exactly. That's why I'm under the impression it's the unknown solution the contractor used. I could be wrong of course.

Thanks for the suggestion will ask my contractor if this was done.

I'm just stumped coz where the stains are, are supposedly treated with water proofing 😣

An active water seepage in progress. Solve the leak first then only apply waterproofing membrane, primer and finally paint.

That outside wall looks like painted, if the paint is weathershield it is good. Also that part of wall seems uncovered and exposed to rain. maybe thats why.
another part you may want to check is what is how is the top of that wall, is it roof with tiles or an extention with cement flab. cement flab means water may gather from there and seep its way down.

if the wall is dry now, do some diy, buy a can of waterproof paste and apply a layer, then paint over. I did that for my back extended wall and seems to work , few years now.
make sure wall is dry, chip off whatever clay/flaks first.
however i did the same for a inside wall where the sink is (above) and sharing wall with neighbour, it didnt help. too wet and cement is basically clay already. it keeps chipping off.

this type i used, similar but not the same brand