Civil Engineering Reference
In-Depth Information
In this passage we will only deal with the construction of straight runs of stairs. Once
you have the theory behind the construction of straight sections of stairs you will be able
to adapt this to many applications including external stairs. The introduction of landings
to join different runs of straight stairs can simply be built as platforms supported on
posts or short walls.
Legal requirements of staircases
The minimum depth of the tread (the horizontal section of the stair) is 240 mm.
The maximum rise from one tread to the next is 190 mm. This is measured from the
top of one tread to the top of the next tread.
External stairs must be constructed of timber approved for external use, such as
treated pine and many of the hardwoods.
The tread width and the rise should be consistent throughout the flight of stairs.
Variance, particularly in the rise, is likely to cause people to trip when using the stairs.
The specifications of timber to be used in staircase is unlikely to be included in the
timber specification schedule so I suggest you consult your building consultant with
details on the width and height of your proposed stairway so that the correct timber
dimensions might be established. It is not necessary to close in the rise of the stairs,
although in some instances this will assist in the structural support of the treads.
Make allowances for stair installation at the frame stage
It is important that correct calculations be made prior to framing the upstairs floor, and
most certainly prior to lining any walls or ceiling in or about the stairwell.
The staircase that didn't fit
A couple of years ago I was called to the home of an owner-builder who was having
difficulty sorting out his stairs and stairwell. The stairwell ran from the lounge room to a
second living room upstairs. The owner-builder was concerned that he didn't seem to
have enough space to fit in his stairs, and he was right. The stairwell needed to be
extended approximately 300 mm to achieve the required minimum ceiling height. This
meant that one of the upper floor joists had to be removed to lengthen the stairwell.
The cutting of electrical cables
At frame stage this would be a relatively simple adjustment, but in the excitement of the
moment the owner had fitted a beautiful timber ceiling. Part of the ceiling had to be
removed. We all know that timber removed will rarely go back into position like it was
originally. I suspect that this is another one of Murphy's laws. There were electric cables
in the vicinity, so great lengths were taken to count them to see that all were accounted
for prior to cutting the ceiling. You guessed it, within seconds of starting the cut there was
a bright flash and the smell of smoke. Thank God for safety cut-out switches or it could
have been very serious. An electrician had to be called in to repair the damage. More
money and more delays.
