Acrylic Paint on traditional house

[Anonymous]

I'm just about to buy a traditional house in Devon that is constructed
of Cob.

However the survey has highlighted that the exterior is painted with
acrylic paint. Enquiries with the vendor reveal that said paint is
actually Dulux Weathersheild.

Anyone know about the suitability of this paint for Cob houses?

Thanks in advance.

H

 

[Anonymous]

It is totally unsuitable as the cob now cannot "breathe". Someone with more knowledge hopefully will answer as well. Not sure if there are some precautions to be taken with regard to removal, ie. you may have to remove and repaint with limewash in one area at a time not all at once.

 

[Anonymous]

Its essential that cod be kept reasonably dry, else it turns to mud and your house collapses. I guess from your question you're a newb to this matter, but the short version is the way to keep it dry is to use a porous paint so it can evaporate dry all day long. Impermeable coatings may reduce rain absorption, but they hinder evaporation much more, so the long term result is a much wetter earth wall.

These sort of coatings are an issue on most old properties, but with mud houses theyre a serious issue. Paint is of course not hard to remove.

Cob is a perfectly good building material, but is a lot more vulnerable than modern materials to mistreatment, so appropriate maintenance is essential.

Here ya go:
http://www.ihbc.org.uk/Cob_Paper/cobindex.html

NT

 

[Anonymous]

The paint is totally unsuitable. However I suspect that the plaster beneath is also the wrong stuff!
Most cob houses down here in Devon have been rendered with cement - theoretically this is unsuitable but I have found plenty that are as dry as a chip despite the horrible stuff.
You might be lucky and find that the acrylic has been applied over an old lime or mud plaster. If this is the case it will just scrape off. You could then just re scat the walls and use limewash as the finish. Mike.

 

[Anonymous]

If it were my house I think I would only use limewash but just for the record I e-mailed this question to ICI after failing to find any useful technical data on their website.

Is Dulux Weathershield a suitable treatment for the exterior of a traditional cob house in Devon?

They replied thus:

Dear Mr Vernon,

Thank you for your enquiry. Yes our Weathershield Masonry Paint is semi vapour permeable so it is fine. The first coat should be thinned down with approx 10% water as the surface is likely to be a little porous.

I hope this helps

Buddy Butler
Technical Advisor
ICI Paints Customer Care Centre
ICI Paints, Wexham Road, SLOUGH, Berkshire. SL2 5DS
Phone: +44 (0) 1753 556956
Fax: +44 (0) 1753 556988
Visit our web site at http://www.dulux.co.uk

 

[Anonymous]

I'm not so sure they were being helpful. Semi vapour permeable means its not vapour permeable, ie it will allow a lot less evaporation than a lime paint. And evaporation is whats neded for earth walls.

NT