Coloured or traditional render and Copperas Lime wash

For discussions about topics related to Period Property in the UK

Moderators: Simon Wright, RobT

Post Reply
Bombay Redeye
Posts: 4
Joined: Thu 3rd Feb, 2022 11:59 am

Coloured or traditional render and Copperas Lime wash

Post by Bombay Redeye » Thu 10th Feb, 2022 7:43 pm

Hi, first time post and can’t believe I’ve only just discovered this forum after living in Georgian properties on and off for nearly 20 years!

Anyway, I’m hoping somebody with experience can help?

My current property of 7-8 years is a regency workers terrace with lower ground area. The facade is largely the original lime render, but when the lower ground was “modernised” in the 80s, the lower ground render was replaced with concrete based render, which is now failing. The render in other places has cracked and been poorly repaired and the whole thing painted in Sandtex!

As a result, the whole thing is being stripped and re-rendered. My aim being to replicate a more authentic ashlar style frontage. For ease of maintenance, I had originally opted for a coloured lime render solution. However, I came across this post


Where I discovered the Copperas finish. This is exactly what I was looking to achieve so I contacted my contractor about maybe changing the coloured render (light grey/white colour) to a 3 coat traditional render and copperas lime render. Now here’s the kicker, add 50% to the cost! I understand the extra effort and maintenance of a traditional render approach and copperas lime wash both initially and moving forward. The renderers have not come across copperas previously and has asked whether I would use a couloured render and limewash this as this would basically be the original cost.

So after all this, I have a few questions which I’m hoping can be answered or at least guided upon as lime render and options, particularly copperas is new to me and want to make “the right” and most appropriate decision. If a traditional render system is the goto solution, I would try and stretch, but it might not be possible unfortunately.

So if anyone can help?

1. Can you limewash coloured render effectively to change its colour? Particularly to create the copperas effect over a white/light grey render?

2. Are there any drawbacks/advantages of a traditional 3 layer render compared to a coloured render solution

3. When applying a copperas wash to an ashlar lined render, to create the effect in the post, do you apply the copperas to each “block” separately or apply across multiple “block” simultaneously as you would if the render had not been lined? I would likely be limewashint the render myself as a cost saving (and personal pride in creating the effect!)

Thanks if you’ve read all this and for any suggestions or thoughts you may have. I want to try and be as authentic and original as I can, but an extra 50% cost for a traditional render approach if I can copperas wash a coloured render and achieve the same effect is a consideration. I’m just a bit lost at the moment! Cheers

Posts: 306
Joined: Tue 25th Jan, 2011 4:37 pm
Location: Somerset

Re: Coloured or traditional render and Copperas Lime wash

Post by TheForge » Wed 16th Feb, 2022 9:19 pm

Copperas is not a render but a surface coating historically applied to lime renders, stuccos and stone. It’s ferrous sulphate in water, sometimes with lime but often without as a simple wash.

The colour and effect in the link could be achieved with most pale pigmented lime washes. It would normally be applied across an elevation or area and the variation results from natural variations in moisture within the substrate.

Bombay Redeye
Posts: 4
Joined: Thu 3rd Feb, 2022 11:59 am

Re: Coloured or traditional render and Copperas Lime wash

Post by Bombay Redeye » Wed 16th Feb, 2022 10:14 pm


Thanks for the clarification. I guess I was trying to see if I could get the effect direct in the render without additional (and then every 5-10 years thereafter) washing. I have since done some additional research on the process but had not come across a copperas mix which is just Iron sulphate and water without lime added.

Since I posted, I have created a sample render board and ordered Copperas Tint (lighter) and Copperas limewash samples from Ty Mawr. I am currently in the process of washing these samples in various numbers of coats to see what effect I like.

Very useful to know that it is applied to a whole frontage area and not ashlar “stone by stone” which will make application more straightforward.

I guess my only real outstanding question is given the significantly more wallet friendly quote for a coloured render compared to a 3 coat nhl render, whether copperas can be applied over a light coloured render and whether the effect would likely be the same as application over a 3 coat nhl render?

I have also been told that the final coat of the 3 nhl coat will be rougher than the coloured finish. Is this correct? The current original (as far as I can tell) lime render from circa 1830 seems smooth enough for the ashlar effect to me.

Thanks again

Post Reply

Who is online

Users browsing this forum: No registered users and 9 guests