Thoughts on design

Musings on architecture and landscape design

Stair diagrams

There are many design considerations involved in making a great stair, but I thought I would start with the practical, I.E. the ease of using them.

The general rule of thumb for a good stair is that the sum of two rises and one run will add up to about 25”,  and that is the ratio I like to use.  Now there is a bit of flexibility on this and I have seen up to 30” being sited at the higher end (for landscape stairs) and 24” at the lower end.  A 23” ratio is going to start feeling a bit awkward, so if space is tight still try and stay with a minimum of  23 1/2″ to 24”, that extra 1/2″ to 1″ does make a difference.

Generally speaking landscape stairs should allow for a longer stride then interior stairs because we tend to take longer steps when we are outside.  A 27” ratio is a normal target for site stairs.  A 6” rise with a 15” tread or 4” rise with and 19” tread are the ends of the typical range

A shallow slope may use extra wide tread that allows for an extra stride between each step.  An average stride is some ware in the 28 to 32” range.  Generally these landscape stairs should also have a shallow treads of  4 to 5” so a tread may be 38 to 42 inches long to provide for the extra stride.  Be careful not to make them too short or you will find yourself doing stager steps one short one long as you go up the stair.

For long tread stairs lite the one above you will be well severed if you can lay a few treads of the stair out and try them out to get the run adjusted to your stride.

Code requires certain minimum standards as well. Most jurisdictions require a minimum rise of 4” and a max rise of 7 3/4”.  The minimum tread depth run is 10” on a straight run of stairs, and on winders it is 10” at 12” out from the inside turn with a 6” min. width at the inside edge.  Spiral stares can be more compact but I won’t go into that here.

Head room is critical and the minimum is 80” measured from nose of the stair treads, don’t forget that carpet and wall finishes take up height!  An 80” clearance feels low and tight and should be avoided if possible, just going up to 84” will make the stairs feel more comfortable to use.

This entry was posted on Monday, January 4th, 2010 at 6:14 pm and is filed under Technical. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.