Grade
Beams
Grade beams and modified foundations
are used when it is determined that soil conditions are not stable
enough to support columns or gates. There is always a small amount
of movement in columns. This is due to their large amount of concentrated
weight on top of foundations that have a relatively small footprint.
A column can weigh four to six thousand pounds (1814 2700
kg) and the foundation can weigh another four thousand pounds.
With eight to ten thousand pounds of material sitting on top of
three square feet (one square meter) of area there is high probability
for settlement.
Grade beams are highly recommended
for double gates (bi-parting). Keeping the alignment in double
gates is much more critical than single gates. When double gates
are hung from columns there is good probability that they will
loose their alignment within a short period of time.
Foundations can be modified to prevent
settlement by altering their size and depth to accommodate soil
conditions. If you are in doubt of your soil conditions you may
want to consult with a soils engineer.