Breathable silicate paint or limewash

[stuwlam]

Hi, I'm looking for some advice on what to use on our brick and stone walls once we have completed all our repairs. The mortar throughout is lime and the walls are solid and must be breathable when finished. I spent a few months last winter removing the smothering cement render from the walls.

The initial thought was to limewash - its cheap, has been used for thousands of years and is easy to apply............. BUT, we live 750 feet up in the Shropshirte Hills where winter winds and rains can batter our house at times, so I am a little concerned that the limewash will not last long, especially on the most exposed elevations.

Thus I've been looking at alternatives and have arrived at Beeck silicate paint which has been used in Germany for over 100 years and chemically bonds to the wall surface, meaning that it is very durable and is claimed to last 20 - 25 years before needing re-treatment.

My concern is BREATHABILITY. Of course limewash is extremely breathable and would have been what coated the house originally (there are still traces of it). But, not being very technical I don't know how much to trust the claims that these silicate paints are breathable and I don't want to undo all my good work and end up sealing moisture in the walls.

If anyone has experience of these materials and could offer me an opinion, I'd be very grateful.

 

[Keithj]

I've used Beeck on the plinth of our house. I was assured by the technical folks at Beeck that it's breatheable (see the Beeck website for more). It's a bit of a faff to put on - what with acid treatment to remove the sinterskin, then washing that off after a few seconds, and so on. It must be done "by the book" or the results will be poor.
The finish on ours is good, so I reckon I got it right.

I'm told that although Beeck recommend 20 - 25 years between treatments, there are houses in Germany that were treated with it over 50 years ago and are still fine.

The chemical process is different from limewash: this stuff changes the calcium hydroxide or calcium carbonate into calcium silicate. The process cannot be reversed, so make sure your Conservation Officer is happy about you using it.

 

[stuwlam]

The process cannot be reversed, so make sure your Conservation Officer is happy about you using it.

Thanks Keith, happily we are not listed!

I had a look at the Beeks data sheet and as far as I understand it, since I am applying it to brick and stone I would only need to apply a primer of Beeck Fixative followed by two coats of Beeckosil paint - so no acidic etching fluid is required on this type of surface. They specify that for new plasters or for cleaning old plasters. Or am I mistaken?

 

[Keithj]

You're probably not mistaken! I was being very cautious, because if you get it wrong, sometimes there's no easy way back.

Beeck have been around for ever, and I've seen lots of historic houses in Germany that have been treated with it. It seems to be good stuff.

We're looking at that, versus Keim, versus limewash, versus do nothing on a Grade 1 listed 13th Century church. The DAC favours "do nothing", although the outside of the building is a motley mix of colours, most of them looking like decay. We would rather pick up the predominant colour in the walls that aren't covered in algae or mould. We're doing test patches to see what works.

 

[stuwlam]

Thanks Keith. I'll certainly double check with the supplier before starting if we go down that route.