Matching 1930s internal rendered walls

Hi all, first post here.

I've recently completed a renovation of my 1930/40's apartment in Melbourne. As part of the works we had to extend a few internal walls, where the original finish is a beautiful and smooth bagged render (to the best of my knowledge).

My builder had a renderer contact – and based on the other trades he'd brought in – I trusted they would do a good job. Off the bat, they renderer said it wouldn't be possible to exactly match the existing render, as they could not replicate the technique used in the initial build. But they said they should be able to get somewhat close.

Before painting, the newly rendered sections appeared to be fairly similar, but after everything was painted, it became clear that there was a fairly noticeable difference between the two. The original is much smoother, whereas the new sections feel a lot rougher more granular. The 'cavities' in the new render are much more noticeable.

It's also worth noting that the original sections have quite a thick layer of paint (when I chipped of a tiny bit it was actually possible to see a "profile" of around 2-3mm) whereas the new paint was done via spray which is very thin.

So, my question: is it possible to fix this in any way to match more closely? Can the new render be sanded back and repainted? Or is there a way to 'fill in' the new render? Alternatively, is this something that can be solved by applying much thicker coats of paint?

I have included some photos of different sections for reference. The new render is on the right of each image. I know a 100% match is not possible, but even a 25% improvement would make a difference!

Thanks in advance.

You have to remember that the original walls probably have been painted 5-10 times over that period so of course any imperfections are going to be filled with paint. Your new sand/cement render should have had white set plaster troweled over it to allow for this prior to painting but then it may look much smoother than the original part.

Stewie

It's incredibly hard to match textured finishes. There are so many variables that makes it almost impossible.
It definitely looks like the new finish has more "texture" as compared to the existing.
As Stewie pointed out the years of existing paint on the old surface has probably helped to fill and hide some of the original texture.
Maybe try using a high build undercoat similar to the one below and give the new area's multiple coats to help fill it a bit. Give a light sand between coats.