What type of render is this?

[JordanH]

Hi all,

Doing some investigation into a penetrating damp issue we are having downstairs when we experience very heavy driving rain (happened twice in the last 3-4 months).
I've been working through stripping off the old masonry paint and have discovered what I believe (very limited experience) is two different types of render, sand and cement at the side, and the original lime at the rear. Both are experiencing the issues, but the rear could be vent, boiler flue, window sill etc. The side elevation is having issues as few metres from where I've taken photos and it's blown in places.

Side elevation -

https://imgur.com/2jjRrZ3

https://imgur.com/QnAGn5F

Rear elevation -

https://imgur.com/0LqIYaJ

https://imgur.com/dyc3vAT

Any thoughts on the above? Also, am I okay to do a coat with a NHL 3.5, or am I better off going completely back to brick on these sections first (side elevation)?

For reference, this is a Victorian terraced solid brick construction, dating back to around 1870.

 

[aockenden]

The side elevation is the one you believe to be cement, right? And you’re wondering if you can just render over that existing cement with lime?

I definitely wouldn’t recommend it, that sounds like a total bodge-job. Doing so makes the new lime render ontop of the cement basically worthless as it’s not in direct contact with the underlying masonry to pull / wick moisture out of the wall and help it dry out. The underlying cement layer will prevent moisture from moving out of the wall and into the lime and then evaporating back out into the air. I would also not be surprised if the two layers delaminated from each other, or you got major cracking on the new lime render ontop, as the materials of the two layers having radically different hardnesses and flexibilities.

 

[alexander]

it looks like two different types of cement render one probably applied when the Holland damp proof course was installed, would be interested to know what is happening on the outside of the wall,