Finishes for hempcrete - The Hempcrete Topic: Designing and Building with Hemp-lime - page 400

Plastering on to hempcrete
Cast hempcrete formed with shuttering is the perfect background on which to apply plaster,
since, if constructed properly, it has the following attributes:
It is very flat, making the process of applying finishes easier, and keeping costs of (po-
tentially expensive) finishes to a minimum.
It provides a very consistent surface across the whole of the wall, which again makes
the application of finishes much simpler.
Its open-textured surface provides an excellent key.
This last reason makes cast hempcrete a particularly suitable base for lime finishes, as
these require a good strong key. The most commonly used finish for a hempcrete wall is
therefore a simple two-coat lime plaster. As described earlier, advice on the most suitable
finish to use should be sought from your hempcrete binder and/or natural building mater-
ials supplier (depending on whether you are plastering direct on to hempcrete or on to a
carrier board), but the following example describes the general method for applying a ba-
sic lime plaster to hempcrete and wood wool board.
If plastering on to a cast hempcrete ceiling, a glass-fibre reinforcing mesh is required (see
page 243 ).
When plastering with lime, the absolute minimum ambient temperature required is 5 ℃ ,
but effectively the working temperature range is between 8 ℃ and 22 ℃ ; below (or above)
which the plaster dries too slowly (or too quickly).
You will need the following tools and equipment:
A standard bell cement mixer.
Clean buckets in a range of sizes: standard buckets for measuring materials; large
buckets or Gorilla Tubs for transporting and storing mixed plaster.
A plasterer's bath may be useful for storing large amounts of mixed material.
Plastering trowels: steel laying-on trowel of a size you are comfortable with, and a
variety of margin trowels, corner trowels as required, and a bucket trowel.
Foam rubber floats , of coarse and fine grades, and a wooden float or metal grid
float.
Plasterer's hawk.