Rendered Garden Walls Damp

[Prav]

Hi All

 

I've just had a garden wall rendered. First drop of rain it looks like this.

 

The wall itself has been there for 20 years.

 

Any ideas on why the mortar between the capstone is so porous? Is this normal? Any suggestions on what I can do to prevent water ingress (top and bottom) before I paint the wall?

 

Thank you 

 

[Radian]

So you never noticed the bricks being damp even though they were. Shows up a treat now. To me the damp at the bottom looks mostly like rain splashing back up from the paving. I say that because the stripe on the RH wall gets wider further forward (the opposite of the slope of the ground). In fact the wall looks well clear of the soil at the very front where the damp is at its deepest.

 

As for the capping joints they could easily be raked out and repointed with a strong SBR added mortar mix to make it waterproof. But if there's no horizontal/vertical  DPC there's always going to be some damp in the render. You may be able to mitigate the problem with a silicone topcoat. I expect someone else here may step in with some advice on that.

[Roger440]

Id hazard a guess that the cap stone have a groove on the underside to stop the water tracking back to the wall. I forget the correct terminolgy.

 

The motar probably doesnt have that so water tracks back. Extend the groover through the motar with a grinder. Job jobbed.

 

As Radian says, suspect the bricks were damp. Assuming its a cement based render, id expect that to fail at some point.

[Simplysimon]

1 hour ago, Roger440 said:

I forget the correct terminolgy.

anti capillary drip

[Prav]

Thank you.

[Prav]

Any thoughts on whether I'm better off leaving the render bare so water can evaporate or paining it and trapping the water? Recognising both most likely will end in disappointment. 😞 

[Temp]

I think if you do render it look for one approved for use below DPC?

[Gone West]

9 hours ago, Prav said:

Any thoughts on whether I'm better off leaving the render bare so water can evaporate or paining it and trapping the water? Recognising both most likely will end in disappointment. 😞 

I had an old garden retaining wall which was damp and I painted it with Durbocem and it has worked extremely well. I do have drainage holes at the bottom though, but I guess you could drill some drainage holes in yours.

 

https://andrewscoatings.co.uk/shop/interior-exterior-walls/damp-mould/durbocem/