RHS Limited
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I wish I had a pound for every time I have had to explain the workings of this Building Regulation requirement that is much loved by Local Authority inspectors. Long ago someone on the Building Regulation committee (probably after a bad night) came up with the idea that little children could get limbs caught in the gaps between the guarding rails or the open risers of stairs.
"Fair enough" you say but who really cares "that’s what children are there for" I hear you cry. Well this chap did care, and he came up with the devious idea that it should be a rule that no gap on a stair should allow the passage of a 100mm diameter sphere. Just to muddy the water a little it was further decided that this rule need not apply to stairs in buildings which are not likely to be used by children under 5.
Quite who decides which buildings this applies to, is confusingly not mentioned in the Regs. As you are probably now aware I am no fan of this rule, it seems to me to create a problem that probably never existed, and then made a pig’s ear of solving it. However who am I to say, you will rarely meet an inspector who will give you leeway on the 100mm sphere rule.
You have been warned, you might have seen lovely minimalist modern open tread, non balustrade stairs on Grand Designs, but forget them, they will be a non starter with the inspector. The only safe bet is a full vertical baluster stair with spacing of less than 100mm.combined with a timber or metal riser bar kit between the open treads if it is an open riser style staircase.
I have had a long conversation with Mrs Winston who wants to put a stair access to her loft space with the very minimum use of space (don't we all). Unfortunately the concept of a space saving stair is a difficult one to grasp for a lot of people. So I suggest to her to look at say a Karina (alternate paddle shaped treads) which saves about as much space as any stair short of a ladder or fireman's pole.
The response I get is "I do not like the look of that, I want a proper stair". Unfortunately life is never that simple, proper stairs take up as much space as any main stair that you find in any modern house. You cannot cheat on the geometry. Building Regulation compliant stairs are designed to give safe access, and that requires a minimum amount of space to stand on each tread, a maximum amount of step up between each tread, and a maximum angle of pitch of the whole stair.
When you apply these rules you will end up with no room to save any space. The only way to save space is to go steeper with your stair, and the only way to achieve enough tread to stand on with a steep stair is to use the paddle shaped treads that you see on space saver staircases.
So it is case of what will fit your space rather than your ideal stair. But do not despair space saver stairs are more comfortable to use than you imagine. They even can comply with the Regulations in certain circumstances, but seek advice on this before you buy.
The Staircase Doctor writes,
I am often asked about using a spiral staircase as a space saving method of gaining access to a loft conversion. This is in most cases a misconception, a regulation compliant spiral is likely to take up as much floor area any other compliant stair, it is just a different shape.
The situation gets even more complex when you look at what the stair serves. There are different requirements for spiral stairs serving say one bedroom or more than one bedroom.
For instance a spiral staircase serving one room needs what is called a clear width of 600mm.
The clear width is defined as the distance from the outside of the centre pole to the inside of the handrail. In practise this requires a stair of 1400mm or 1500mm in diameter depending on the stair construction. Where as a spiral staircase serving 2 or more rooms needs a clear width of 800mm. Again in practise this equates to a spiral of around a whopping 2000mm in diameter.
Probably the reason that you see so few spirals in large conversion projects.
Let us be honest spirals look great and add a wow factor to any loft project. No one should be put off using a spiral, but you have to realistic about the amount of space they will use. As with all stairs they are more complicated than what you think, and it is advisable to seek professional advice early in the design stage.
Never plough on with the project under the assumption that you get a stair to fit in that corner somehow, it always ends in tears.