Week 7 - Passivhaus Design Blog

 Passive Design

Stairs

In my design for my home I have a second floor, with it being a story and a half, so there must by a way to access this floor. I have decided just to use stairs as it is the most effective solution, a lift would conserve some space however requires a complex installation process, where stairs are simple and can also be a defining feature of a home. Below you can see in my floor plan where I have decided to put my stairs in my dwellings and have decided to use a quarter-turn form to conserve space.

Performance criteria for stairs includes:

• Safety - they should be safe to use.
• durability - they should resist the wear and tear of everyday use.
• fire - the stair should be enclosed with fire-resisting storey-height construction.
• aesthetic- they should add to the space and its appreciation.

Safety

Although I have most of the choice when it comes to the form, materials and little details that make a feature of the stairs, the main practical features in a stair like handrails and things like that are driven by safety considerations and building regulation requirements. With stairs all being designed with these tight constraints it means that when you go to walk on a stair, no matter where it is, it comes naturally and you can do it without looking down. If a stairs step rise were to be too high people would trip. This consistency is what makes all stair feel the same and makes them safer for people to use. below is images of stairs with all its different parts labelled. 

Guidelines for stairs

handrails/guarding:

• stair width <1,000mm = 1 handrail
• stair width >1,000mm = 2 handrails
• should give firm support
• should not have any elements that would provide a foothold
• wall handrails should be at least 38mm clear of the wall

Stair pitch:

• pitch line should be a max of 42° but its optimum pitch is 35°.
• Headroom should be greater then or equal to 2000mm at where the stair pitch line meets the ground floor.
• the height of the banister after the newel post at the top of the stairs should be < or equal to 1100mm.
• A sphere of 100mm should not pass through the balusters.
• from the pitch line to the top of the handrail should be between 800mm-1000mm.

Rise (r):

• vertical distance from the surface of the thread to the surface of the surface of the next thread.
• max rise 200mm.
• optimum rise 175mm.
• 16 max risers in any one flight.

Going (g):

• horizontal distance from nosing to the next nosing.
• min 220mm.
• optimum 250mm.
• nosing should be greater then or equal to 16mm

Gait formula: 2r + g = 550-700, optimum of 600mm

Stairs calculations

For a straight forward flight of stairs without an intermediate landing, the stairs demensions are calculated in three steps:

1. divide total rise by 16 or less.

• maximum allowable number of rises is 16.
• rise must be less than 200mm.
• aim for a round number.

      2. Optimum going is 250mm.

      3. Input these values into the gait formula to check if twice the rise plus the going is between 550-             700mm:

• If necessary adjust number of risers or going length until gait formula is satisfied.

My stairs is not a straight flight so it will have to calculated slightly differently, below are my calculations.