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Paint peeling along outside render


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Posted

I noticed a while ago paint peeling along the bottom of our 5 year-old bungalow.

I was a bit complacent, assuming it was simply poorly applied paint over badly prepared render, but after trying the wire brush, cement stabilizer, then silicon gradually poured into a line of holes along the render, then more stabilizer, I finally accept there is a real problem, presumably rising damp.

There is now a 'salt line' and furring about 20cm up from the path in isolated patches (there is a concrete path around the house, no soil touching the walls). I've noticed the render is crumbly in a few places, presumably weakened by the chemical reaction, so even a chemical dpc may not work.

I suppose the 'nuclear option' is to get the render hacked off back to solid concrete, paint on a water block layer, then re-render with a waterproof additive. Most of the walls seem stable now (after my earlier work?), so the areas to re-render would only amount to about 5 sq M, (I've read that rising damp can reach 1.2 M above ground, but mine isn't anything like that).

The DIY stores have shelves of chemicals; BesBond Cement Super Flex, a 2-pack resin membrane, looked okay for the barrier coat, but I don’t really know. For the cement additive TOA 211 (or any PVA product) seems popular on other TV discussions.

I would appreciate any thoughts/ideas.

Thanks.

Posted

If it is crumbly, then something wasn't done properly.  Maybe strip away some render and see what the underlying concrete looks like.  If that is in the same shape, you may have a serious problem.  

Posted

Not saying this will solve your problem, but I used SikaTop Seal 107 to seal the render in the pool.
Maybe read the brochure and see if it could be applicable.

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Posted
On 12/1/2017 at 3:12 PM, bankruatsteve said:

If it is crumbly, then something wasn't done properly.  Maybe strip away some render and see what the underlying concrete looks like.  If that is in the same shape, you may have a serious problem.  

I have hacked off a small section, around the worst area. The underlying concrete looked okay, so hopefully it's only the render that's faulty.

Posted
On 12/1/2017 at 3:41 PM, carlyai said:

Not saying this will solve your problem, but I used SikaTop Seal 107 to seal the render in the pool.
Maybe read the brochure and see if it could be applicable.

Sent from my SM-J700F using Tapatalk
 

Thanks. I checked that product on YouTube, and it looked similar to the BesBond - a 2-part resinous slurry. The video showed it being applied as a sealant finish. I wonder if it can have render applied over it, or paint? Whatever finish I end up with has to be paintable.     

Posted

From your description i can say 100% its not rising damp its rain splashes and bounce from the rain onto the wall.

As you have rightly discovered risingdamp will travel up a wall but often no more than a metre but you should also have picked uo that rising damp and efflorescence salts never go together its usually caused by 

Condensation or penetrating damp.

Internally heat can draw moisture from the new structure and cause paint to blister.

Here its the sun...so a new home is really going to blister at any height as heat draws moisture and salts out.

I think you have a partial penetrating damp problem but the splashes are just getting behind the paint.

You will get the efflorescence and you will get condensation mould around the bottom.

Best solution is to wire brush off and use a bleach solution to kill the mould.

Protect the bottom 300mm with a silicone water repellant but then if possible try and create a splah barrier with a strip of gravel or something.

My guess is that your worst walls will be the ones which generally get the brunt of the rain.

Posted
Thanks. I checked that product on YouTube, and it looked similar to the BesBond - a 2-part resinous slurry. The video showed it being applied as a sealant finish. I wonder if it can have render applied over it, or paint? Whatever finish I end up with has to be paintable.     
Yes you can render over it. We SikaTop Seal ed the poured pool walls and floor, then rendered over the top. My guy used a trowel to apply it in small day by day sections. You can also brush it on. Need a good mask, eye protection and those red long plastic gloves.

If you think you have a render problem, use a rubber mallet or the blunt end of a screwdriver and tap tap tap along the wall; you will hear a different sound if the render has not taken well to the structure.
I'm glad I did it with the pool, some sections did not take.

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Posted
On 12/5/2017 at 5:09 PM, eyecatcher said:

From your description i can say 100% its not rising damp its rain splashes and bounce from the rain onto the wall.

...

Thanks for that. Interesting. I thought one of the possible signs of rising damp was a white 'tide line' of salts being pushed out by the moisture? But yes, I'm not certain what the cause is. A builder's been round and is going to hack off the worst areas of render and take a look.   

Posted
On 12/6/2017 at 7:05 AM, carlyai said:

Yes you can render over it. We SikaTop Seal ed the poured pool walls and floor, then rendered over the top. My guy used a trowel to apply it in small day by day sections. You can also brush it on. Need a good mask, eye protection and those red long plastic gloves.

If you think you have a render problem, use a rubber mallet or the blunt end of a screwdriver and tap tap tap along the wall; you will hear a different sound if the render has not taken well to the structure.
I'm glad I did it with the pool, some sections did not take.

Sent from my SM-J700F using Tapatalk
 

That's helpful to know about the SikaTop. I just have to decide which one to use. 

I did the 'tap' trick, and there are areas of blown render. Whether caused by moisture behind it or bad application/bad mix should become clear once the builder hacks off the worst of it.     

Posted

When Thai builders mix their own concrete they can be a little shy with the stone. If you can drill a hole in it and the drill goes through like drilling butter, there's no stone in it. So when the painters paint it, they are actually painting sand and cement. Anybody else experienced this?

Posted
3 hours ago, RickBlaine said:

Thanks for that. Interesting. I thought one of the possible signs of rising damp was a white 'tide line' of salts being pushed out by the moisture? But yes, I'm not certain what the cause is. A builder's been round and is going to hack off the worst areas of render and take a look.   

Another clue for rising damp is that you would see the tide mark inside the house also.

Posted
3 hours ago, RickBlaine said:

Thanks for that. Interesting. I thought one of the possible signs of rising damp was a white 'tide line' of salts being pushed out by the moisture? But yes, I'm not certain what the cause is. A builder's been round and is going to hack off the worst areas of render and take a look.   

I apologise; and you are correct I have actually written salts when I should have written mould.

Of course salts can travel up through the structure and be deposited on the surface.

I had better stop digging now and remove my building surveying qualifications from my name.

Posted
On 12/7/2017 at 7:53 PM, vogie said:

When Thai builders mix their own concrete they can be a little shy with the stone. If you can drill a hole in it and the drill goes through like drilling butter, there's no stone in it. So when the painters paint it, they are actually painting sand and cement. Anybody else experienced this?

Our render is only cement (and sand), not concrete, but the paint should still stick to it. The render is 'like butter' in places where it's blown, and will be coming off soon. 

Posted
On 12/7/2017 at 10:58 PM, eyecatcher said:

I apologise; and you are correct I have actually written salts when I should have written mould.

Of course salts can travel up through the structure and be deposited on the surface.

I had better stop digging now and remove my building surveying qualifications from my name.

We don't have any discolouration inside the house, but like most modern Thai houses ours sits on a concrete plinth, raised above the ground, so the internal walls are well above the 'salt line' outside. I've just been watching some YouTube videos about the 'myth' of rising damp and how the chemical DPC industry is a con. So maybe you're right, it's not rising damp (I wouldn't hang up your theodolite just yet). We've obviously got a problem but, going back to the original post, whether its just poorly applied render or something worse is still to be ascertained.   

  • 3 weeks later...
Posted
Our render is only cement (and sand), not concrete, but the paint should still stick to it. The render is 'like butter' in places where it's blown, and will be coming off soon. 


Why would render have stone in it?
How would you get a smooth wall finish with great lumps of stone in it?
Isn't render always sand and cement only?



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Posted
6 hours ago, irlguy1 said:

 


Why would render have stone in it?
How would you get a smooth wall finish with great lumps of stone in it?
Isn't render always sand and cement only?



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I have seen rendering done with aggregate up to 5mm size. Obviously it isn't smooth, it doesn't need to be.

Posted
I have seen rendering done with aggregate up to 5mm size. Obviously it isn't smooth, it doesn't need to be.


Render is the smooth finish on internal and external walls. The final coating that you paint over. Of course it has to be smooth.


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Posted
6 hours ago, cooked said:

I have seen rendering done with aggregate up to 5mm size. Obviously it isn't smooth, it doesn't need to be.

Is that what is called 'silang' here? Decorative render?

Posted
6 hours ago, irlguy1 said:

 


Render is the smooth finish on internal and external walls. The final coating that you paint over. Of course it has to be smooth.


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Why does it have to be smooth? If you want the exact term, it's pebble dash.

Posted
Why does it have to be smooth? If you want the exact term, it's pebble dash.

Pebble dash render and render are two different things [emoji4]

Pebble dash is also not something done very often in Thailand which is crazy considering how bad the regular render usually is.

Pebble dash would avoid all the ugly cracks.

 

 

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Posted
50 minutes ago, irlguy1 said:

Pebble dash render and render are two different things emoji4.png

Pebble dash is also not something done very often in Thailand which is crazy considering how bad the regular render usually is.

Pebble dash would avoid all the ugly cracks.

 

 

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To be honest I find the render quality here pretty good.

 

I showed my builder how to spatterdash and render with sharp sand (red sand on little its/clay brick). Also explained that the cement strength should get weaker if rendering in layers.

Posted
4 minutes ago, grollies said:

To be honest I find the render quality here pretty good.

 

I showed my builder how to spatterdash and render with sharp sand (red sand on little its/clay brick). Also explained that the cement strength should get weaker if rendering in layers.

Weaker in layers? In the West all render jobs are done with a scratch coat then final.

Posted (edited)
21 minutes ago, Thaitoknow said:

Weaker in layers? In the West all render jobs are done with a scratch coat then final.

Spatterdash 2:1, render 1st coat (scratch coat) 3:1, 2nd layer 3.5:1 portland cement.

Edited by grollies

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