Even if custom wooden stairs are to be installed, portable stairs should be constructed as soon as possible. Stairs are designed to move people and material more efficiently and safely.
Whether building permanent or temporary stairs I like to install them as early as possible in the house framing process. Normally while the upper floor is being sheathed.
Having steps available as early as possible in the framing process will save time and energy for the rough framers. This time and energy can then be applied to the ultimate goal of finishing the framing job in a safe, timely, and cost effective manner.
Fast Stairs is a company that sells modular adjustable steel stair stringers. These can be purchased by builders and moved from job to job as the need arises. Wooden treads supplied by the builder are then screwed to the steel stringers.
The wooden treads can then be easily removed if they become damaged or the set of stairs need to be disassembled and moved to a different job site.
They also sell steel hand rails that bolt to the steel stringers. Meeting OSHA safety standards, in a safe and cost effective manner.