Improving the water tightness of a wall

[gejohesch]

Here is my problem:

 

-          A wall in a house owned by my wife (in Isan) is not watertight. When it rains heavily, water “sweats” inside of the house. Fortunately, not too much, but the resulting dampness does not feel good nor healthy, plus it gradually ruins the paint.

-          The wall was built with “blocks” which were not well cemented. Usually, I see such walls get “surfaced” with smooth cement on both sides, but in this case that was only done on the inside. As a result, water can easily penetrate the wall.

-          It would be straightforward to get a worker to do that cement “surfacing” on the outside, but here is the actual problem : the wall in question was built (regrettably) too close to another wall and it is not possible to get into the space in between (it’s only 20 cm wide). Therefore, I’m looking for a solution that would involve doing “something” on that wall from inside the house.

-          Could I for example cut openings at regular intervals in the wall, stick my arm out and “surface” the outside, then plug back the openings? That sounds like quite an effort but I would only have some 3 or 4 square metres to do.

-          I am vaguely aware of more sophisticated techniques such as injecting resin into the wall, but as I understand it, that is really something to leave to an expert (obviously, I’m not myself an expert), and that would likely be costly too.

 

Any suggestions? Thanks in advance!

[Encid]

On 11/26/2022 at 11:15 AM, gejohesch said:

It would be straightforward to get a worker to do that cement “surfacing” on the outside, but here is the actual problem : the wall in question was built (regrettably) too close to another wall and it is not possible to get into the space in between (it’s only 20 cm wide).

Would it be possible to hang some plastic sheeting on the outside of the wall to prevent the rain water from wetting the outside wall surface?

As the walls are so close a plastic sheet is unlikely to degrade due to sunlight.

[Cake Monster]

Get the outside wall rendered over correctly, and when fully dry paint inside and out with a silicon sealant paint such as " Thompsons Waterseal "

The Waterseal is a UK product, but I am sure there will be an equivalent in Thailand.

[DaLa]

First thoughts are why with only a 20 cm gap it's getting that wet. Usually an overhang of the roof should give the wall some shelter.  Personally I wouldn't want to be creating an additional inner surface as that's just going to trap the water . I ran my own construction business in the Uk and never liked the idea of giving advice if I couldn't view the situation, so if possible find someone with some knowledge and let them view the issue. Finally is there any way to get a roller on a long pole down into the gap to 'treat' the area. If so Thai Watsadu have multiple products that can help with waterproofing.  By the way waterproofing is all you will achieve, most buildings aren't watertight.

 

Sorry I cant't be of more help than that. 

[gejohesch]

14 hours ago, Encid said:

Would it be possible to hang some plastic sheeting on the outside of the wall to prevent the rain water from wetting the outside wall surface?

As the walls are so close a plastic sheet is unlikely to degrade due to sunlight.

I thought of doing sthg like this, but I don't think it would be possible to do it well enough as there are some 4 metres to do along the wall and the gap to the other wall is only 20 to 30 cm, i.e. access to do the thing right is just not there.

[gejohesch]

14 hours ago, Cake Monster said:

Get the outside wall rendered over correctly, and when fully dry paint inside and out with a silicon sealant paint such as " Thompsons Waterseal "

The Waterseal is a UK product, but I am sure there will be an equivalent in Thailand.

As said, rendering the outside is a major issue due to limited access. I keep your suggestion of using a silicon sealant paint inside, however, thanks.

[gejohesch]

14 hours ago, DaLa said:

 

"First thoughts are why with only a 20 cm gap it's getting that wet. Usually an overhang of the roof should give the wall some shelter."

Good comment. I did not mention that the other wall gets to a neighbour. We would not want to extend the roof over that wall so as not to get all the rain water into the neighbours! I know, I know, it was very silly to build so close to the neighbour in the first place, but now it's done that way, we are not going to bring the building down!

 

".... never liked the idea of giving advice if I couldn't view the situation, so if possible find someone with some knowledge and let them view the issue"

Good advice!

 

"Finally is there any way to get a roller on a long pole down into the gap to 'treat' the area. If so Thai Watsadu have multiple products that can help with waterproofing.  By the way waterproofing is all you will achieve, most buildings aren't watertight."

Sounds like a good idea indeed. Interesting comment "waterproofing vs watertight".

 

"Sorry I cant't be of more help than that. "

You have helped a lot already, thanks!

 

 

[HuskerDo2]

14 hours ago, Cake Monster said:

Get the outside wall rendered over correctly, and when fully dry paint inside and out with a silicon sealant paint such as " Thompsons Waterseal "

The Waterseal is a UK product, but I am sure there will be an equivalent in Thailand.

Yes, Waterseal or FlexSeal or Watertight can all help. I'm sure there are many different brands but look hard and you'll find it. I used it on a leaky basement (poor construction) and it completely solved the problem. No more water in the basement.

[sometimewoodworker]

3 hours ago, gejohesch said:

I thought of doing sthg like this, but I don't think it would be possible to do it well enough as there are some 4 metres to do along the wall and the gap to the other wall is only 20 to 30 cm, i.e. access to do the thing right is just not there.

The industrial sheeting used by truck drivers will do the job. It is very heavy duty (probably PVC)

As it’s so well made it will easily fall down into the cavity, if you have access at the ends you will be able to tie it down.

These sheets are available it a verity of sizes, l’m sure there are ones longer than 4 metres. They are not cheap but very effective, I bought a small one that is about 2 x 3 metres. Your only problem will be finding the shops that sell them.

[gejohesch]

7 hours ago, HuskerDo2 said:

Yes, Waterseal or FlexSeal or Watertight can all help. I'm sure there are many different brands but look hard and you'll find it. I used it on a leaky basement (poor construction) and it completely solved the problem. No more water in the basement.

Thanks for this. I take note.

[gejohesch]

4 hours ago, sometimewoodworker said:

The industrial sheeting used by truck drivers will do the job. It is very heavy duty (probably PVC)

As it’s so well made it will easily fall down into the cavity, if you have access at the ends you will be able to tie it down.

These sheets are available it a verity of sizes, l’m sure there are ones longer than 4 metres. They are not cheap but very effective, I bought a small one that is about 2 x 3 metres. Your only problem will be finding the shops that sell them.

That's interesting. Thanks!

[Don Chance]

20cm should be enough to get a roller or brush set up in between.

You could use tar or liquid rubber.

https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcQ0lQD3fLW_9GnZyFdnbv2D_9vDvto1ixoCGJdExwbfMA&s

[degrub]

Is access only from the sides or do you have full access from above ?
 

 

[gejohesch]

2 hours ago, Don Chance said:

20cm should be enough to get a roller or brush set up in between.

You could use tar or liquid rubber.

https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcQ0lQD3fLW_9GnZyFdnbv2D_9vDvto1ixoCGJdExwbfMA&s

Yes, the roller idea is a good one. Remains finding the appropriate product to put on the roller. A probable issue here is that the blocks were poorly cemented, it was a sloppy job (not uncommon in Isan), which means that there are lots of small gaps or entry points for water. Not sure just rolling some stuff over the wall will be sufficient. Maybe I can try to put cement (a liquid enough formula) on a roller first to try to plug the gaps as much as possible, and then do a second pass with water proofing product.

[gejohesch]

2 hours ago, degrub said:

Is access only from the sides or do you have full access from above ?
 

 

Well yes maybe, but that would require some work on the roof first, which I could not do myself. Of course, that would be a way to access the upper part of the wall, which is probably the one that soaks in water the most!

[HighPriority]

Can you get a galvanized steel guttering formed up to fit between the two walls and channel the water away ?

 

Or you could purchase a two part acrylic epoxy waterproofing membrane and apply it to the inside wall surface and 300/500 mm of the floor. Such a product is designed as a barrier to rising damp, from memory it can be painted within a day or two but not later.

 

I’m a ceramic tiler and have used a product called Ardex WPM 300 for this purpose, give it a Google.

 

 

[chickenslegs]

On 11/26/2022 at 11:15 AM, gejohesch said:

It would be straightforward to get a worker to do that cement “surfacing” on the outside, but here is the actual problem : the wall in question was built (regrettably) too close to another wall and it is not possible to get into the space in between (it’s only 20 cm wide). Therefore, I’m looking for a solution that would involve doing “something” on that wall from inside the house.

Is the "other wall" a neighbouring house, or a just a garden wall?

If it's a garden wall (usually a concrete frame filled with blocks and rendered) AND if you have a cooperative neighbour, you could take out the blocks then properly render and waterproof your wall.

Rebuilding the garden wall afterwards should not be too expensive.

[sometimewoodworker]

5 hours ago, gejohesch said:

Yes, the roller idea is a good one. Remains finding the appropriate product to put on the roller.

 

there is a MrFixit product that does the same job

[HighPriority]

The problem with rolling paint or waterproofing over the outside is that presumably (and in the OP’s opinion the mortar to the blockwork is poor) paint and waterproofing will not fill those voids and water will still penetrate the wall.

By applying a negative hydrostatic pressure membrane to the inside of the wall you stop the moisture getting inside, which is the end goal for the op.

[gejohesch]

13 hours ago, HighPriority said:

Can you get a galvanized steel guttering formed up to fit between the two walls and channel the water away ?

 

Or you could purchase a two part acrylic epoxy waterproofing membrane and apply it to the inside wall surface and 300/500 mm of the floor. Such a product is designed as a barrier to rising damp, from memory it can be painted within a day or two but not later.

 

I’m a ceramic tiler and have used a product called Ardex WPM 300 for this purpose, give it a Google.

 

 

"Can you get a galvanized steel guttering formed up to fit between the two walls and channel the water away ?"

That could be the best idea! Collect the water right below the roofing, where it comes from, and evacuate it.... I will see if we can arrange that. If it can be done, there will be no need to improve the wall further below!

 

"Or you could purchase a two part acrylic epoxy waterproofing membrane and apply it to the inside wall surface and 300/500 mm of the floor. Such a product is designed as a barrier to rising damp, from memory it can be painted within a day or two but not later.

 

I’m a ceramic tiler and have used a product called Ardex WPM 300 for this purpose, give it a Google."

It sounds interesting but, not being a professional at all, it also sounds a bit mysterious, and like the sort of thing I would not be able to do myself. And finding a worker in Isan who would understand the concept and be able to do the job properly..... our village is 10's of kms away from the nearest semi-important agglomeration, most people around here are not used to fancy work.

 

Btw, the more I do work around my wife's 2 houses (quite a nice compound), the more respect I have for professional builders!

 

 

 

 

[gejohesch]

10 hours ago, chickenslegs said:

Is the "other wall" a neighbouring house, or a just a garden wall?

If it's a garden wall (usually a concrete frame filled with blocks and rendered) AND if you have a cooperative neighbour, you could take out the blocks then properly render and waterproof your wall.

Rebuilding the garden wall afterwards should not be too expensive.

It is a garden wall, and it's a pretty good idea indeed. Everything would be fixed within a few days and for a few 1000's baht. I would rather hesitate talking about it to the neighbour, though, we had some issues building stuff elsewhere close to his lot in the past.

[gejohesch]

9 hours ago, sometimewoodworker said:

 

there is a MrFixit product that does the same job

Thanks!

[gejohesch]

2 hours ago, HighPriority said:

The problem with rolling paint or waterproofing over the outside is that presumably (and in the OP’s opinion the mortar to the blockwork is poor) paint and waterproofing will not fill those voids and water will still penetrate the wall.

By applying a negative hydrostatic pressure membrane to the inside of the wall you stop the moisture getting inside, which is the end goal for the op.

Good comment. I thought about that too. However, if I could fill some of the gaps and reduce the water intake somewhat, maybe with several roller passes, that would already be a gain, would it not? As for the hydrostatic pressure membrane, it sounds a bit mysterious to me (as already said) but I will look it up to understand the concept. Thanks again!

[HighPriority]

Most typical waterproofing membranes act a bit like a pool liner, you apply (usually paint) them onto the inside of a vessel (tank, shower wall/floor, pond etc) and the water rests against it and is contained.

If however the waterproof membrane is on the outside of the structure the water seeps through and literally pushes the membrane off the surface as they are just a thick, rubbery paint.

The negative hydrostatic membranes are usually a modified epoxy that makes a better bond to/into the substrate enabling it to withstand the water trying to push it off.

 

As to being able to fill voids in the wall by making multiple passes it really depends on the size of the voids.

In a shower situation you would flush the imperfections with silicone (or cement mortar) and apply membrane over that, small imperfections you could “load up” your brush and fill, but they often open up again on the first/second coats.

To fill poorly mortared block joints with membrane only in a situation where you were forced to only use a paint roller to apply would be a pretty tough ask.

IMHO I’d go with the WPM 300 on the inside of the wall as my preferred coating, but a guttering would beat everything.

[sometimewoodworker]

1 hour ago, HighPriority said:

If however the waterproof membrane is on the outside of the structure the water seeps through and literally pushes the membrane off the surface as they are just a thick, rubbery paint.

That statement doesn’t make sense, as you have your waterproof painted coating on the outside, the rain hits the waterproof coating and falls down. So how is the water seeping through a waterproof coating? Unless the coating isn’t waterproof, and even then it’s remarkably difficult to push the coating off the wall since the surface is rough, and even if the coating isn’t completely waterproof you are not going to have significant water penetration.

 

So please explain more completely as either your concept is wrong or your explanation lacks significant detail 

 

[HighPriority]

6 hours ago, sometimewoodworker said:

That statement doesn’t make sense, as you have your waterproof painted coating on the outside, the rain hits the waterproof coating and falls down. So how is the water seeping through a waterproof coating? Unless the coating isn’t waterproof, and even then it’s remarkably difficult to push the coating off the wall since the surface is rough, and even if the coating isn’t completely waterproof you are not going to have significant water penetration.

 

So please explain more completely as either your concept is wrong or your explanation lacks significant detail 

 

I was trying to keep it simple, but you are correct, I made it too simple.

Essentially standard waterproofing membranes are designed to be on the same side of a structure as the water… the water sort of pushes the membrane onto the surface.

Negative hydrostatic pressure (rising damp) membranes bond so tightly to the substrate that the water and salts cannot push it off (bubbling, lifting or peeling)

The situation the OP is describing is a rising damp type problem, or lateral damp if you will…

If there was access then a surface patch and/or render coat followed by paint would solve his problem.

[sometimewoodworker]

3 hours ago, HighPriority said:

I was trying to keep it simple, but you are correct, I made it too simple.

Essentially standard waterproofing membranes are designed to be on the same side of a structure as the water… the water sort of pushes the membrane onto the surface.

Negative hydrostatic pressure (rising damp) membranes bond so tightly to the substrate that the water and salts cannot push it off (bubbling, lifting or peeling)

The situation the OP is describing is a rising damp type problem, or lateral damp if you will…

If there was access then a surface patch and/or render coat followed by paint would solve his problem.

While the increased explanation is probably useful, I can see no way that it applies to the current situation. I agree that for water tanks you must waterproof the inside.

 

water is falling (not rising damp)

that water is coming through the wall. (The wall is getting soaked, lateral damp, yes)

the waterproof paint will go on the outside 

A waterproof paint will stop the majority, if not all the water penetration of the wall. (No lateral damp)

Qed there is no water in the wall so no hydrostatic pressure against the waterproof paint

 

Certainly if the wall was getting wet from the inside your statements could well be true but it isn’t so they aren’t.

 @HighPriority

please explain how this is not correct 

[degrub]

Another issue to consider is getting the coating to bond to the block substrate. It certainly has to be cleaned of dirt and any friable or spalling surface material and salts and allowed to dry. Usually takes a pressure wash and/or vigorous wire brushing which sounds difficult in this case. 
 

 

[sometimewoodworker]

3 hours ago, degrub said:

Another issue to consider is getting the coating to bond to the block substrate. It certainly has to be cleaned of dirt and any friable or spalling surface material and salts and allowed to dry. Usually takes a pressure wash and/or vigorous wire brushing which sounds difficult in this case. 

It’s far less difficult than you imagine, yes you need to brush off loose stuff and vegetation, no you don’t need it as clean as you suggest. No you definitely don’t need to pressure wash.. I’ve used the product it’s far more forgiving than you think

[HighPriority]

12 hours ago, sometimewoodworker said:

While the increased explanation is probably useful, I can see no way that it applies to the current situation. I agree that for water tanks you must waterproof the inside.

 

water is falling (not rising damp)

that water is coming through the wall. (The wall is getting soaked, lateral damp, yes)

the waterproof paint will go on the outside 

A waterproof paint will stop the majority, if not all the water penetration of the wall. (No lateral damp)

Qed there is no water in the wall so no hydrostatic pressure against the waterproof paint

 

Certainly if the wall was getting wet from the inside your statements could well be true but it isn’t so they aren’t.

 @HighPriority

please explain how this is not correct 

You’re an extremely infuriating man Jerome.

The OP stated that the mortar joints of the blockwork are poor.

Thats number 1 ingress point for water.

It sounds like the wall is 2-4m wide and the space from the neighboring wall is 200mm, so how about you let us all know how you propose to fill all those mortar joints prior to applying the paint or other membrane ?

If the joints are not sealed water will penetrate the blocks and any coating you are thinking of will peel and blister because of the moisture coming in, be it a paint/coating on the inside or outside… which is why I recommended the product I did, because it’s easy to apply from the accessible interior of the room and it will not be affected by any moisture, damp or water. In fact it can be applied to damp surfaces.

Now if you need any further education on the product and why it’s fit for purpose I’ll send you my payID… have a good night ????????