Civil Engineering Reference
In-Depth Information
External line
of building
Centre of
stump hole
Figure 2.5
Profile hurdle for the location of the stump holes and the outside line of the building
An L-shaped house will require 12 hurdles. If your house design lends itself to it, you
may be able to combine two hurdles into one simply by making the cross bar longer.
If this is feasible it will be evident at the time of installing the hurdles.
The horizontal rail of the hurdle will have lines marked on them representing various
construction points on the house. A 50 mm nail is to be hammered into the rail of the
hurdle at the lines marked on it. A string line will be strung between the nails on the two
opposing hurdles as a reference to the actual building line.
Setting out the hurdles for the house location
The procedure detailed below is for the setting out of hurdles for a flat or excavated
building site.
Fit short pegs, ideally 50 × 50 × 200 mm long, into the ground representing the
actual position of the two external corners of the building on one wall. Where it is an
excavated site this will be done for the wall nearest the cutting face. Fit a nail into the top
of each peg to show the exact position of the external corners of the wall. Next we need to
fit a third peg, complete with nail, for an end wall which we will assume is at right angles
to the first wall. You will need two pieces of black cotton or soft string about 200 mm
long to help with the next process.
Determining the right angle
To determine the position of the first two walls of the house at right angles to one
another, fit a string line between the nails on the two pegs that designate the corners of
the building, make sure the string is not fouled on anything that prevents it from forming
a straight line. Measure from one of the nails 4 metres back along the string line. Tie the
cotton or string at the 4-metre mark so that you can refer back to this position a little
later on. With one tape measure, measure three metres from the same nail in the general
direction of the new wall to be plotted. Have your assistant hold the end of a second tape
measure at the cotton tied to the original string line. Extend the second tape measure to
5 metres and bring the two tape measures together. Using Pythagoras's theorem, that in a
right-angled triangle the square on the hypotenuse is equal to the sum of the squares on
the other two sides, where the 3 metres of one tape measure intersects the 5 metres of the
