So measuring up it looks like the treads will be made up of a 3" or so stair nose, one full 4 3/4 width board of and then a ripped down width of board 3" or so.

Question is, do i lay all 3 boards down separately or should i glue them up into one piece and lay it down as one piece ?

I was planning on using construction adhesive and face nailing it for fixing.

Thoughts ?

Thanks

If you have time, you can first glue and fasten the nosing. Then when you are finishing up the next rows you can pry against the riser before you fasten the boards and rip down to take up any slack and get everything tight.
Start with the widest nosing and work the shortest pieces last, in case you make a little mistake, so you can keep the nosing nice and snug to the wall.

I think it would be easier to glue up into one piece. Also, make yourself a stair tread jig so you get a nice fit on the end(s). Construction adhesive and face nail or trim head screws.
If you decide to install the boards separately make the nosing piece a minimum of 3 1/2" wide.....this is a high stress area....I'm assuming you will have an overhang.

Sorry for the delay, work is holding me up from doing my own house,lol yeh i made stair jig, bought the plastic stair jig ends from Home Depot and apiece of wood for in between.

Yeh will be overhanging whatever it says code should be.

Hoping to get stuck into it next week and making one solid piece sees to make more sense

thanks again

There is no code for the projection, or overhang of the tread. Usually the projection is one and a quarter to one and one-half inches so there is room for a scotia molding, which is one-half inch wide and ¾ inch deep. It is nailed into the top edge of the riser. The tread has a rounded edge to help prevent wear and is usually one inch thick or more.

Work has a way of getting in the way of other things.
The overhangs come into play in determining tread depth which is dictated by code.