Weather Protection
Protecting projects from inclement weather is an important factor, the long-term effects of
which may not become apparent until after a job has been finished, when certain elements
start to fail for reasons that are not immediately obvious. For example, grouts may change
colour without evident cause, due to a lack of permeability in the laying bed under the paving.
Water remains trapped within the joint, and only surfaces once sunlight and heat play on the
products. Perhaps the grout became too wet during application due to additional water in the
bottom of the joint caused by previous rainfall that was not properly allowed to dry.
There are three primary causes of failure due to weather problems; too much heat, whereby
cementitious materials are allowed to dry too quickly, thereby losing any grip or integrity
during the laying process; too cold, where temperatures fall below the recommended levels
for use on certain materials, especially chemicals, grouts, adhesives, sealants and jointing
compounds; and rainfall, causing mortar to become overly wet and susceptible to rapid drying
out causing cracking and shrinkage once it does set.
Problems with heat may be alleviated with the use of tentage, preventing direct sunlight from
falling on working areas, and the use of dampened hessian sheets laid over ongoing work,
taking care to damp them down, and not overly wet them, thereby causing too much moisture
to enter pointing joints.
In cold weather, hessian sheets once again are invaluable, only they must be kept as dry as
possible, to prevent ice from forming on the retained water and causing freeze/thaw action.
Whilst rain may be the least problematic, with many options to remove excess water, as far as
protecting work from heavy rainfall, the use of tarpaulins or large plastic sheets is the obvious
answer. Be aware however, of the weight and pressure that a lot of water can have on the
surface of an impermeable sheet can be enormous, and take care to mitigate that pressure by
use of ridges under the sheets, created by pallets, crates, ladders etc, to prevent a build-up
of laying water over an area of recent work – especially newly laid slabs, as the weight will
cause the whole area to subside and settle, even by a few millimetres, which may result in a
dip in the finished work the following day, thus creating puddles in the surface levels. This is
even more important on raised areas or mezzanines, where a retaining wall is supporting the
paving, where downward pressure can cause problems with the walls as well as paving works.
The idea of using timber or similar structures is to channel water across the working site,
towards the lowest point, and not allow it to accumulate in large puddles on the sheets,
ensuring the ridges follow the requisite line of direction of flow
