Civil Engineering Reference
In-Depth Information
Figure 2.3
Cut and fill site preparation
Personally I am not a great supporter of this method of excavation. It is ideal if you
are building a farm shed or doghouse where it matters little if the floor moves and cracks,
but for a house it is important that the foundations are set on solid ground. This method
is fine for a house with stumps, although it may mean that the stump holes are quite deep
which makes them difficult to clean out. The depth of the hole is determined by the
depth into natural ground level as specified on the soil report for the property, not the
actual depth of the hole.
Potential problems with cut and fill excavations.
I have seen many concrete floors that have been poured on a cut and fill excavation that
have cracked. I have a factory in central Victoria that has been constructed in this way
and the floor has cracked. It is not too much of a concern in this application, however it
is a totally different situation for a house. If the floor of a house cracks it will have an
impact on termite treatment, floor coverings and moisture penetration. If the floor
continues to drop and the crack in the floor worsens, it is more than just a little serious.
These are all complications that I would rather do without.
A cracking concrete floor on cut and fill
Some time back I purchased an existing house on acreage in Ravenswood just out of
Bendigo in Victoria. It was a house that needed some love and attention in a position that
suited our needs at the time. I managed to gain a copy of the original plans submitted to
the council for the original building permit, and was amused that instead of the tile roof
specified on the plans the builder had fitted an iron roof. Furthermore, the roof trusses
were set out to carry roof tiles rather than iron. It wasn't until we removed the old carpet
that things became somewhat clearer. There were cracks across the centre of the lounge
room floor from one side of the room to the other - cracks approximately 5 or 6 mm
wide. I was not surprised, for the line of the cracking was in line with the junction of the
fill to the excavation.
These cracks had been filled with an epoxy resin, probably in the early stages of
construction, and there was no sign of further movement. I would assume that there were
some anxious moments for the builder, and an appropriate solution of deleting the heavy
cement tiles and fitting iron instead was the most feasible solution to the problem. This is
not a problem I have ever faced with any of the homes I have built, for I have never built
a home on a cut and fill site. If this was a requirement of the job I have always decided to
allow the customer the benefit of finding another builder.
