On Oct 1, 5:47 pm, 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. I have heard "the glue is stronger
than the wood", but it still is a concern to me.

Any opinions or experience with this?

http://www.stairplan.com/spacesaver.htm
The glue probably won't fail, the wood will fail somewhere. Seasonal
changes will exacerbate the situation with solid wood treads. Either
use a center stringer, use plywood, laminate solid wood to make your
own plywood, or use through-bolts to reinforce the freeboard end.

R