Lime or cement render

Hi

This is causing a bit of an argument within the family. I need some advice.

Without a doubt, this is a lime mortar brick wall, rat-trap bond, Victorian property—one of three in a row.

The external render has been cracked from top to bottom in the middle for many years, with a few horizontal cracks. I set about tackling this last year, knocking off all the blown render towards the bottom and anywhere that sounded dull with a hammer. The majority of the wall sounds solid and is in relatively good condition.

I then raked out the visible soft crumbly brick joints to 25mm and re-pointed with some NHL lime/sharp sand just to get through the winter. The plan this year was to wait until the last of the frosts had passed, then get out and cut out all the cracks big enough to patch, followed by getting a plasterer round to complete the work.

This is where the arguments started.

The last frosts this year were in the second week of April. The following week, before I had a chance to get started, a couple of plasterers were asked round to quote—without my knowledge.

One plasterer has told my family that this is not a lime-rendered wall, but cement! Red flag?

He has quoted for a complete cover of K-rend over 60 m² of the gable end wall, but I personally believe this is not the right option to use on a Victorian property. K-rend is cement-based, and I feel it will cause problems down the line.

The attached photos show the external render ( can supply more photos if needed) along with an internal wall where I removed the gypsum plaster (which had blown too). It has all been left to air over the winter, with the plan to stud it out and use 75mm sheep’s wool insulation and breathable materials on the inside.

How can I confirm whether this is cement or lime render? All three properties are rendered the same, this is not a modern addition.

I'm concerned that K-rend will cause internal issues. While it may stop water from entering the building, it's not going to breathe and allow moisture to escape. Applying a 20mm (approx guess.) K-rend skim over the gable wall could be prone to cracking in future if the house continues to move. The house already sufferes from high humidity ive mesured its at over 80% at times of very wet weather due to the cracked render. With it being a small 2-up 2-down property, it affects every room.

"The plasterer has been booked for September :( I'm trying to stop this before we waste a lot of money.

Is K-Rend suitable or not?"
What problems will arise from using this?
Lime render or cement is there a way to test?

(Thanks for reading)