Civil Engineering Reference
In-Depth Information
permit will specify that you need to have the stump holes inspected prior to laying the
stumps. The bottom of the stump hole must be basically flat and be free of all loose
material. This is often a somewhat frustrating and time consuming job so don't fall into
the trap of calling for the inspection the same day as you dig the holes. I would suggest
that you contact your building surveyor once you have arranged the time of the digging
to topic the inspection for the following day.
There have been owner-builders that were impatient and did not wait for the stump
holes to be inspected prior to laying the stumps. Do not be mistaken and think that you
can bypass this inspection. If you lay the stumps and build the floor on top of them
without an inspection of the stump holes you WILL be dismantling all your work and
cleaning out the stump holes for the inspection.
Sole plates: materials and installation
Let me first clarify terminology. When I speak of foundations I am not speaking of the
concrete, timber, or other materials that we put into the ground, rather the earth that
these materials are positioned on. I am told that the pressure applied by a 65 kg woman
wearing stiletto heeled shoes is greater than that of an elephant's foot. The reason of
course is that the load of the stiletto heel is focused on a very small area, whereas, while
the weight of the elephant is obviously much greater in total, the load is spread over a
significantly bigger area of its four big flat feet. The purpose of the sole plates under
stumps is to give the house elephant feet. That is, to spread the load over a greater area so
that the stumps will not puncture through the earth in the bottom of the stump holes.
Refer to the approved plans for details on the depth and diameter of the holes to be
dug for the stumps. The bottoms of the stump holes need to be free of any loose material.
If the sole plate is fitted on loose material, the loose material will compact under the
weight of the house and cause the sole plate to drop, thereby causing the house built on
the sole plates to drop. Your building permit calls for a stump-hole inspection. The
inspector will be checking that the holes are of the correct diameter, that the holes are
down into solid material as described in the soil report, and that the holes are clean of
debris and loose material. The soil report will describe the material in the ground that is
deemed as providing a solid foundation. It will also specify the likely depth of the holes to
establish a solid base. While digging the holes it is crucial that you ensure that the soil
described in the soil report is accessed. The depth of the hole is secondary to the material
in the bottom of the hole.
Timber sole plates
Timber sole plates are only used in combination with timber stumps. While timber has
limited capacity to support a heavy load it is a very simple sole plate to install. Most
weatherboard homes built in the last hundred or so years will have been built on timber
sole plates. The most common timber used for sole plates is Red Gum, Cypress Pine and
Jarrah. When installing timber sole plates it is important to ensure that the bottom of
the hole is not only clean but also flat. Refer to your approved plans for details on the
materials and required size of the sole plates. Commonly the sole plate will be 250 × 200
× 50 mm. The sole plate is to be positioned in the hole so that the stump will sit near
