Placing hempcrete - The Hempcrete Topic: Designing and Building with Hemp-lime - page 361

When the first shuttering comes down, go along the wall and check for consistency and
any tamping mistakes evident in the face of the wall. When training up a placing team,
it can be helpful to have each person responsible for placing in a specific section of wall
on the first day, so that when reviewing the success (or otherwise) the next day, you know
who did which bit. Needless to say, this should be less about 'naming and shaming' than
about knowing where to target your teaching and supervision on the second day of placing.
Look for the following errors visible on the surface of the wall:
If the whole wall is too open, loose and crumbling, then it wasn't tamped enough.
If it is too closed and dense everywhere then it has been over-tamped.
If some layers are well tamped, but interspersed with loose layers, then too much mix
has been poured in at one time. This means that when it was tamped down, the top of
the layer was compressed but not the stuff underneath.
If there are empty pockets, or unfilled hollows visible, then the mix has not been spread
around evenly before tamping.
Gather your team around and show them the difference between different results, and make
it clear what you are aiming to achieve. Ensure that everyone understands the issues relat-
ing to the closed versus open surface, render costs versus drying times, and breathability.
Occasionally, and especially with an inexperienced team, you may take the shuttering
down to find that there are a few small areas where you can see empty holes on the surface
that haven't been filled properly, or which are filled with very loose hempcrete. These
areas have not been tamped properly, creating a very low density of finished material that
will not be strong enough to support the render or plaster.