Why are my bricks so wet?

[Mike66]

I was concerned about a gap that had formed between my concrete path and the wall of my house. Over time the path has sunk and now slopes toward the house, so during rainfall I was worried that water might be running into the gap and potentially causing damage to the brickwork or leading to damp issues inside. (This was checked and no internal damp problems were found.)

To address this, I cut a channel and will be installing channel drains. Since doing this, I’ve noticed something unexpected: after rain, the bricks in that area are now becoming very wet, seemingly through capillary action. This never happened before, even when water was running straight down the gap.

I’ve now realised that the bricks below the original pathway level are exposed, and quite a lot of the mortar has come out of those joints. Could this be the reason the bricks are now getting so damp (as shown in the picture)?

I assumed installing a drainage channel would improve things, but it seems to have made the wall wetter. Any ideas why this might be happening? And do you think I am doing the right thing by installing the channel drains? Thanks in advance.

[Redbeard]

I don't know how likely this is, but try it:

 

Previously you had just concrete. I assume the top pic is 'before'. Now you have mud and broken concrete. It looks as if mud has splattered up the wall and has imparted a layer which absorbs water. So is it that the bricks area completely soaked through, or that the 'mud overcoat' is wet?

 

BTW, you said

8 minutes ago, Mike66 said:

(This was checked and no internal damp problems were found.)

As this is a cavity wall you might not see damp internally even if the ext wall was wet. This was, after all, the original idea of cavity walls, that a failure properly to maintain the external skin would not automatically result in damp internal conditions for the tenants ('tenant' used advisedly as experimentation with cavities started in 19th C when the private rented sector accounted (if I remember my Housing lectures properly) around 90% of the housing stock. (I accept, of course, that that cavity in your pic may well have been retro-filled if it is, as I guess, c1960s).

[Mike66]

Hi, it is definitely the bricks that are wet. And the property is 1970s and there is a cavity wall that is filled with a foam type substance. And yes, the top photo is before I decided to take the concrete up. I have attached another photo that shows the underneath bricks with a fair bit of mortar missing.