Civil Engineering Reference
In-Depth Information
The timber panelling had to be removed
At first glance it appeared that all that had to be done was to cut back the ceiling, re-
framing the upper floor joists and refitting the ceiling. But there was more. The owner
was fabricating his own stairs to save money: a common practice for owner-builders. He
had already fitted the stringer of the stairs and brackets to the stringers in their
theoretical position to take the treads. It was when fitting the brackets that he realised he
had a problem. The stringers and brackets had to be removed and refitted in a lower
position. Unfortunately he had already fitted his beautiful timber panelling complete
with dado mould to the wall of the stairwell. The timber panelling had to be completely
removed, but this time there was no saving it, for it was now too short.
A day was lost waiting for the electrician, and it could have been a lot longer. Four
days were lost altering the ceiling height of the stairwell, and another to fit the new wall
panelling on the walls. The stair stringer had to be replaced, as did all the panelling for
the walls. There was significant financial loss in the whole process, but that was the lesser
of the cost. The highest cost was emotionally. The disappointment and frustration at
having to destroy his pride and joy took a heavy toll. It is sometimes difficult to look past
a problem that is so daunting; this can often bring the job to a sudden halt.
The theory behind the construction of straight stairs
1. Establish the total height the stairs are to traverse
This is equal to the distance from the surface of the finished floor at the bottom of the
stairs, to the surface of the floor at the top of the stairs. Divide the height by 190 mm,
which is the maximum rise permissible. Round the answer up to the next full number.
This will be the number of risers required in the staircase.
For example:
2.6 metres high that is,
2600 mm
Divided by the maximum rise
190 mm = 13.8
Rounded up to the next full number
= 14 risers
2. Establish the actual rise of each step
Divide the total height by the 14 risers
For example
Total height 2600 mm
Quantity of risers
14 = 186 mm
3. Establish the length required in the stairwell
An ideal width for the tread is 280 mm however you may not have the total length
required of the stairwell to accommodate this. The quantity of treads is one less than the
quantity of risers, so in this example it will be 13. To establish the total required length to
accommodate a 280 mm tread, multiply the tread width by the number of treads.
For example
Proposed tread depth 280 mm
Quantity of treads
× 13
Required length of stairwell
= 3640 mm or 3.64 metres
