Placing hempcrete - The Hempcrete Topic: Designing and Building with Hemp-lime - page 368

and only if local conditions are favourable and the correct mixing and placing techniques
are followed. Additional factors, such as the time of year and on-site management of dry-
ing (see Chapter 19, page 264 ), will also have a significant effect on drying times. For ex-
ample, in particularly wet climates or at colder and wetter times of year, drying can take
significantly longer. Sustained wet weather brings the double problem of it being harder
to prevent excess water entering the wall during mixing and placing, and less-than-ideal
drying conditions.
It is important to get accurate estimates of drying times for the specific binder you are us-
ing from your material manufacturer or supplier, based on the exact thickness of wall you
are proposing to cast, since a quoted time of, say, 6-8 weeks for a 300mm wall does not
automatically mean that a 400mm wall will take 8-11 weeks. In other words, increasing the
thickness of a wall by a given amount can have a disproportionate effect on drying times;
you can't assume that there is a linear relationship between the two.
Given the importance of drying times and their potential effect on the schedule of works,
you really need to get as firm an idea as possible of the drying parameters right at the start
of planning your build. In this way, sensible decisions can be made about material choice,
and even about the thickness of walls, in the knowledge of how these will affect the project
schedule. It is worth keeping in mind that drying times are not so critical with a cladding
or rain screen finish, as the vented cavity will continue to bring air across the face of the
hempcrete, and staining does not in any case affect a cladding finish.