Stair Gradient Advice

[nerissa]

I am a set designer wanting to use an set of open stairs to reach a 2m platform. I want them to take as little space up as possible. What is an advisable gradient so that actors can still walk upright safely up & down them rather than them becoming more like a ladder? There is likely to be a hand rail on one side.

 

Ta for any advice given,

 

Nerissa.

www.ncargillthompson.co.uk

[Rob]

There's a formula that architects use which I can't remember off hand, but basically, it uses the height of each riser and the depth of each tread. I would imagine that ideally you want to aim for no more than 200mm high for each riser and about 300mm of depth for each tread.

[Brian]

The rules from the building regulations for domestic stairs are...

 

1. The height of any rise should be no more than 220mm

 

2. The going of any step should generally not less than 220mm

 

3. The pitch should be not more than 42 degrees (which means you cannot have both maximum going and rising). This is measured from the ground up to the stair line.

 

4. For any step the sum of twice its rise plus its going should not be more than 700mm nor less than 550mm

[Rob]

Aah, That'll be the formula then!! As stated elsewhere, handrails are ideal on both sides, especially if you're using a steep pitch.

[Brian]

of course, if you need to save space you could always use alternating steps.

[robloxley]

of course, if you need to save space you could always use alternating steps.

Not the easiest to walk up or down though.

[Cyclonic]

Basically never go beyond 45 degrees or you could get into difficulties, if someone breaks there leg you could end up in court. But it is possible to do steeper, but at your own risk.

[Brian]

(Brian Fairchild @ 15 Jul 2003, 08:11 AM)

of course, if you need to save space you could always use alternating steps. 

 

 

Not the easiest to walk up or down though.

 

True. I had a lot of trouble the first time I used some. The trick was figuring out which leg to start with.

[Spock]

If you have access to a copy, "Scenery: Draughting and Construction" by John Blurton has a very useful chapter on staircase design for the theatre.

[Piers Shepperd]

I've been stuck with this problem many times, and although building regs do offer a starter, you can with the necessary risk assessments and clearance go far steeper. I started looking at regs for ships and gantrys with limited access (i.e. not for the public), and you can then start getting far steeper.

 

You must remember you are entering a very vague area liability wise. I've usually completed a risk assesment, using the following main arguments as to why I deviated from building regs;

1) Access is not for the public, and numbers are strictly controlled

2) Professionals using the design will be trained and made aware of the risks

3) Other professionals will be on hand to assist (e.g. stage management team).

4) The design is not a permanent feature, but a temporary one with a very limited lifespan.

5) The local licensing team have reviewed the design (either on site, or prior to installation), and have agreed to your proposals.

6) Extra handrails

7) Adequate lighting

8) Non slip surfaces

9) Review process to change your plans if their are problems in use

 

The important thing is for everyone on the team (including the people using the stairs) to be made aware of the risks and ensure they understand what you are proposing and what could go wrong e.g. falls and trips resulting in non fatal injury, but possibly broken limbs. The key to this process is pushing the creative and design teams to understand what problems they are creating when asking you to design items like this. I've found that if a director / production manager has the possible risks explained to them, then their ideas can be changed.

 

I'm very keen to push the limits of what we can do backstage to the limit (otherwise every design will be based on 8'x4' steeldecks 2' high!). This means creating a design environment which can manage potentially risky ideas in a safe process. This takes time and enormous levels of commitment.

 

Rant off and facts:

 

In a recent backstage staircase completed in the west end for a bandplatform with very limited space (we will rock you), I used the following;

 

150 going (step depth), 250 rise (vertical spacing). The handrail was approx. 900mm above the front edge of each tread. (overall angle is perhaps 65deg) This proved to be very steep but they were usable. Also try not to make them very wide (maybe only 850mm), so that someone can easily use both handrails for support (note handrails on both sides are very necessary when considering this).

 

I use a very good book as a starter point for these tricky situations:

neufert - architects' data third edition. ISBN 0-632-03776-8

This book is expensive but offers good sketches and dimensions for many problems.

 

Piers