# Forum Home Renovation Stairs, Steps and Ramps  Help with stair calculations please

## alpina

Hi all, 
Thanks for the previous advice on risers. 
I've tried a few calculators and have not been able to get a decisive answer on designing my stairs. Hoping you guys can please assist. 
Hope I get the terminology right so here goes it  :Smilie:  
I have a 3 level commercial building which will have stairs along the right hand wall from ground to 1st floor and directly above from 1st floor to 2nd floor. 
Height from ground floor to top of 1st floor is 4350mm and from 1st floor to top of 2nd floor is 3425mm. 
I want to use a steel stringer design down the center with cantilevered stone steps. Left wall will have a combination of steel rods or glass acting as the ballustrade. 
I understand that clear tread width needs to be a min 1000mm and that I have to allow 100mm each side for handrails (50mm extension rod from wall and 50mm handrail), so total width can't be less than 1200mm. 
I dont want to use any risers but understand that given the number of steps involved that I will have to put a nose on each tread as riser gap cannot be more than 125mm. 
Have I gotten all this right? 
If so, can anyone tell me what the ideal design would be to meet BCA requirement? What will be the total length of each staircase be and how many steps will each staircase have? 
Also, not sure what the rule is in regards to penetration hole above each staircase ... think I remember reading somewhere that you need a minimum 2mt headroom ... Is this correct? 
Thanks, 
B

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