May 22nd, 2012 by Tim Leave a reply »

Most of what makes a good set of stairs or steps comes down to the initial planning  and there are a few important pointers that must be heeded to ensure this (most come directly from the SA National Building Regulations).

Here they are:

  • No rise of any step should exceed 200mm
  • The going or width of each tread should not be less than 250mm.
  • If the treads are open (no solid risers), each tread must overlap the lower tread by at least 25mm.
  • The variation in the risers or dimensions of the widths of treads should not be more than 6mm per flight.
  • Maximum slope 45 deg (preferably less)

It is amazing how often these simple rules are ignored and the result is almost always noticeable and often ruins an otherwise perfect deck, house etc.

So how do we go about this? Well it’s simple really:  first measure the overall horizontal and vertical distances you have. Divide the height by 200mm, this will give the number of risers you need. Round this number up to nearest whole number and then redivide the height by this number. This will give the actual riser height required. Now take the number of risers and subtract one, this will give you the number of treads needed (the first tread is the ground so you need to subtract one).  Remember each rise can only be a maximum of 200 mm, so if it’s not working out (number of treads multiplied by 250mm is too wide) then you will need to steepen the staircase. The only way to do this is to overlap the treads – don’t simply reduce the tread width to below 250mm as often is done!

Here is an example :

vertical distance = 1290 mm / 200 mm = 6.45 therefore we need 7 risers : 1290 mm / 7 = 184 mm per riser.

7 risers – 1 = 6 treads x 250 mm = 1500 mm overall width!  Check to make sure we have room. Either widen each tread (flatten angle) or steepen by introducing a tread overlap. Just remember guidelines above!

In terms of practical construction considerations there are a number of ways to go about constructing the stairs but I decided that cutting the rise and tread into each support was the way to go.  I used 2 pieces of timber and joined them to give sufficient depth of timber after each slot had been cut out (in South Africa you battle to get check timber wider than 225mm). I used a 225 x 38 + 115 x 38 to give it some strength and joined them by screwing 100 mm long screws though the 225 into the 115 at each tread at the riser interface (narrowest point).

Once you have one marked out and cut, you can use it as a template for the rest. (just remember to subtract for the thickness of the decking planks!)

To support each support I chose to cast a small concrete foundation to which I anchored some angle brackets. This made life easier as each support could be adjusted individually to make sure they line up.

Here are pics of what I did, enjoy: