Finishes for hempcrete - The Hempcrete Topic: Designing and Building with Hemp-lime - page 421

Limewash is a very cost-effective option, but it is more temperamental than paint, and for
a successful limewash that will not dust when dried you need to be surprisingly accurate
about the proportions and obsessive about mixing it well before every use. Our preference
is to use paint inside and limewash outside.
Limewash can be bought from traditional building suppliers, but is very easy to make by
diluting 2kg of lime putty in 2 litres of water. Varying amounts and mixtures of lime-tol-
erant natural pigments (e.g. ochre, burnt umber or sienna) can be added to the limewash to
colour it, or it can be used in its natural milky-white state. Limewash keeps very well, but
it is important to stir it well before each use as the constituent parts tend to separate out
quickly.
Limewash on the external walls of a building is first applied as at least three to five thin
coats, and probably more if a pigmented limewash is being used. The finish is then main-
tained with the application of further coats as necessary over subsequent years. How often
this is required depends on the skill with which the initial coats were applied, as well as on
how it is weathering, which in turn depends on the orientation and exposure of the build-
ing. Much research has highlighted the role of limewash in the repair of heritage buildings,
not just in colouring but also in protecting and preserving masonry and render.
Truly breathable paints will usually be mineral-based, often lime or clay. It is worth doing
your own research on what works best for you and your build, and indeed your pocket,
as more and more products are coming on to the market. Our favourite paint currently for
indoor use is a clay paint called Earthborn, which we find to be cost-effective, attractive
and breathable. In contrast to other clay paints on the market, Earthborn is a truly natural,
breathable clay paint which contains no acrylic. We find that this paint is so thick that it
can be watered down by 20 per cent and still provide a super-matt thick clay finish, which
seems more like a very thin coat of clay plaster than a paint. Another option is silicate
paints, which can provide a very hard-wearing and breathable solution for both internal
and external applications. In particular these can be a comparatively low-maintenance al-
ternative to limewash for large buildings, where the initial outlay of using these paints is
outweighed by avoiding the costs of access to re-apply limewash on a more frequent basis.
As well as the very important issue of breathability, it is worth keeping in mind that paint
is one of the main ways in which toxic chemicals are introduced into our living environ-
ments. Because of the proximity of paints to us, i.e. being on the surface of the wall rather
than buried deep inside it, any chemicals present within paint pose a much greater risk than
other synthetic building materials of contaminating our immediate environment or coming