several of my stairs are giving way. also beleive that the stringers are bad, one is cut in sections and stairs feel very weak.
Question - are stringers cut the same way as they are for decks??
Essentially, yes- they are done in the same way so if you've done one you can do the other. If you can remove an existing stringer intact it will make your pattern and make the layout work simpler. Remember to not over-cut with a circular saw; leave as much wood intact as possible and if you can reinforce the stringers with sistered 2X4 or 2X6 lumber. I go a little 'overkill' with interior stringer strength and stairs because so much is involved in making repairs (and often the loss of materials in the needed demo) that it's just not worth chancing anything in any way. Here is where doing the very best you possibly can is the only way to lasting success.
A reliable framer will cut you new stringers, calculating the "unit rise" and the "unit run" according to your total rise and run. Code says that max rise is 7.75". Knowing that you will know how many stairs you need.
Divide the total rise (in inches) by 7.75. round the result up to the next number. Now divide the total rise by that number - and you get the unit rise.
How many stringers you should have depends on how wide your stairs are.
For safety sake, try to use the stairs as little as possible.
Given the dimensions, a local lumber yard might cut the stringers for you
With a router, a template, and a few years of training, you can make your own housed stringer staircases and save some bucks.