Steel spiral stairs

• May be allowed as internal or external means of escape stairs if not more than 50 persons using it . 
• Give a very compact arrangement and used where plan area is limited . 
• handrails are continuous and convex in cross section of polished metal , painted metal or plastic covered . 
• Have 12 or 16 treads to complete one turn around the central core
• Terminate at floor level with a quarter circle landing or square landing . 
• Stairway circulation width must be completely clear of any opening doors . 
• Treads and landing plates should have a non-slip surface and be self draining . 
• Standards pass through one treads and are secured on the underside of the treads , giving strength and stability to both handrails and steps . 
• (25 x 25 landing newel )
• (tread unit fitted over central tube and sealed with metal putty or similar )
• (20 x 20 bottom newel ) .