Civil Engineering Reference
In-Depth Information
unwanted heat and airflow. Installing the flashing loosely could reduce the negatives, as
bulk insulation could then be fitted between the flashing and the window buck. While
this would reduce the problem I personally prefer to leave this application method to the
brick veneers and weatherboard homes.
The water that flowed uphill
Back in the eighties, the owners of a house in Adelaide contacted me somewhat distressed
as there was trickle of water running down the inside of their lounge room wall. Not a lot
of water, but water just the same. It had not at this point done any notable damage, but
obviously could not be left unchecked. The relative lounge room wall was virtually in the
centre of the house, and as this was a new iron roof I was somewhat at a loss as to where
the water could be coming from. I started my investigation at the water discharge point. I
looked in the roof immediately above the point where the water was coming down the
wall, but there was no water present, nor any sign of water having been in that area.
We determined that the problem only occurred after light rain, and that it was not
until a good deal of time after the rain started that the trickle of water in the lounge room
occurred. The fact that the problem only occurred during light rain gave direction, as this
is a telltale sign of water flowing uphill by cohesion. The back section of this house had a
reasonably flat roof, which could contribute to the problem, however this was nowhere
near the point that the water was running down the wall. We set up a soaker hose (a type
of garden sprinkler) on the roof to emulate the falling of gentle rain. We quickly discovered
that the water was not discharging cleanly from the end of the iron into the gutter.
In one place only, the water was running under the edge of the iron and following the
rib of the iron back into the roof cavity. It followed the iron slightly uphill for about two
metres and then dropped down onto the sizalation. It gathered there until sufficient
water was built up to reach a hole in the sizalation. From that hole it fell to the ceiling,
which was about four metres from the trickle down the lounge room wall. Unfortunately,
the water was dropping onto the ceiling at the junction of the cornice to the wall. The
water then ran around between the wall sheeting and the cornice until it found a tiny
hole in the cornice adhesive, which happened to be immediately above the trickle line on
the lounge room wall.
I had been unable to see the water from within the roof cavity, as the ceiling sheets
just happened to extend almost all the way through to the wall sheets thereby concealing
the top of the cornice. The solution was simple. We bent the end of the iron down
thereby increasing the pitch of the roof at its very end. The water would then discharge
off the iron with greater speed. Furthermore, the increased angle at the end of the iron
was too great for the water to flow back up. So you see, water really can flow uphill!
Installing timber architraves to seal the sides and top of timber windows
The sides and top of timber windows that are fitted at the external extremity of the wall
can be sealed by fixing timber architraves to the face of the window which then extend
across the face of the rendered wall (see Figure 10.5). This should be fixed in place after
the second coat of render has been applied so that the straw below the timber architraves
is completely sealed. Again the surface of the architrave should be treated with the glue
and sand mix to reduce the likelihood of separation cracks between the timber and
