Thoughts as to what this is on top of original render?

[jsmac]

Hello,

Having removed numerous layers of conventional masonry paint built up over the years from the front elevation of our house I've encountered several mm of 'something' that has been spread over the original render.

The property started its life as a small Georgian cottage and was then expanded in the 1880s. We've unpicked and prodded nearly every square foot of the building so we're confident that the render is original, but I can't work out why large sections of the render have been covered with this putty-like substance. I've knocked it off in places and the render behind it is sound so why (or when) this work was done is beyond me.

It will be hugely time consuming to get it all off (took me about 5 hours to remove less than 2 sq foot) but from what I can surmise that will be the only way to get a satisfactory final finish. Any thoughts on what I'm looking at and advice of a method to get it off would be greatly received.

Many thanks.

 

[a twig]

Looks similar to a very hard cement slurry we had on our stonework, took 4 weeks with an angle grinder and vanity discs to remove it all, strippers, DOFFS etc didn’t touch it

 

[jsmac]

As way of an update and in case someone sees this post and finds the same rock hard stuff coating their render we found a solution...

The technical folk at Restorative Techniques suggested that the cracked putty-like layers of coatings were likely oil-based paint layers, which was a traditional treatment for stucco. Seed and fish oils were used but most commonly linseed oil. They suggested softening the layers of old paint with their polyurethane paint softener and then removing them with a DOFF or Thermatech machine. This is what we tried and it worked! The PU softener worked very well and although we had to go over it multiple times with the softener and DOFF machine we were able to get back to the original render eventually. It was cold, wet and messy work but we got there in the end!

 

[Kearn]

As way of an update and in case someone sees this post and finds the same rock hard stuff coating their render we found a solution...

The technical folk at Restorative Techniques suggested that the cracked putty-like layers of coatings were likely oil-based paint layers, which was a traditional treatment for stucco. Seed and fish oils were used but most commonly linseed oil. They suggested softening the layers of old paint with their polyurethane paint softener and then removing them with a DOFF or Thermatech machine. This is what we tried and it worked! The PU softener worked very well and although we had to go over it multiple times with the softener and DOFF machine we were able to get back to the original render eventually. It was cold, wet and messy work but we got there in the end!

Was going to say the hazing looked like an oil based finish - hard nasty stuff wouldn’t do that, it would just crack at best. The guys at RT are great - send in a sample for analysis for the cost of postage! Helped with cleaning the plastic paint off our brickwork…