I'm trying to help out a friend with a wall.

Plan is to lift off the coping stones and relay to stop water getting in to the wall from above.

Looking at the way the black streaks start at the crack near the top of the wall in the second picture it suggests water is getting in from above and then exiting from the crack.

Render below the cracks feels very solid while above sounds slightly hollow.

Once the coping stones are back on would it be best to replace the blown render above the crack and then repaint over the lot?

Will there be issues with discolouration when painting over and what can be done with the section where the climbing plants have left their mark?

 

An option could be to try and remove all the render and redo but I can see it being a nightmare to get all the render off.

What about going over the whole wall - is their some sort of preparation that would allow rendering over the whole wall?

Edited August 28, 20215 yr by jfb

Once the coping is off, get rid of the top mortar course and any blown render.  Set a strip of DPC at least 20mm wider than the wall into a mortar bed and then more mortar and stones back on.  That way, if any water gets through the joints in the stones it will be sent on its way by the DPC.  The vegetation can be brushed / scrubbed off before you paint.

Do you need mechanical fixings on the copes now?

Once repaired pressure wash the lot to get all the black stains off before re painting.

16 hours ago, Mr Punter said:

Set a strip of DPC at least 20mm wider than the wall into a mortar bed and then more mortar and stones back on.

So that you would see the 20mm DPC overlap from underneath?

 

great suggestions everyone thanks.

1 hour ago, jfb said:

So that you would see the 20mm DPC overlap from underneath?

 

 

Yes.  10mm each side.