david blumberg wrote:
hi,

Alternate tread stairs are for steep applications, such as to a loft. I
was asked to build a set for someone. The tread width is 24", the depth
for the wide half is 10", reducing to 4" for the narrow half. Thickness
spec'd at 1 1/16". Housed in the stringers (1 1/2" thick). Material to
be ash, maple, or birch...

My question is: Due to the depth of the tread, I would need to glue up
narrower boards to make up the 10". As the front of the tread is only
supported on one side, I am concerned that someone stepping on the tread
could snap it off at the glue joint.

That could be why the manufacturer, in the example you cited, uses 24 mm
Birch plywood for the treads.

--
Jack Novak
Buffalo, NY - USA