How to Calculate Stairs

7/25/2019 How to Calculate Stairs

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How to Calculate Stairs

Here is a quick and easy way to work out your stair requirements.

First, take a look at the regulations that we can use as a starting point for working out our risers

and our going.



For the purpose of the following examples we will look at the regulations for Private Stair.

Example 1

Determining the risers

Aove we have a change in level that requires a few steps. !here is a floor to floor level of

"#$mm.

%f we refer to the regulations we can choose a riser height etween &#$mm and ''$mm.

!ake the minimum riser height of &#$mm. (ivide the overall change in level )overall rise* y

&#$mm.

450mm / 150mm = 3

!his tells us that with a riser of &#$mm we will need + riserssteps.



Perhaps we decided we would rather have ' steps instead of three. -e can divide the change in

level y the amount of steps we want

450mm / 2 = 225mmHaving two steps will give us a rise of ''#mm which according to the regulations aove would

e over the maximum allowance for a riser. So in this case we have to have a riser of &#$mm

giving + steps.

Determining the going / run

As indicated in the regulations aove, a normal relationship etween the dimensions of the rise

and going is

Twice the Rise plus the Going (2R + G) should e etween ##$mm and /$$mm

!o continue with the previous example let0s select a low going of ''$mm.

!his gives us 2 150mm + 220mm = 520mm

As we can see from the guidance aove, it is recommended the outcome is etween ##$mm and

/$$mm

So let0s now try '/#mm



2 150mm + 2!5mm = 5!5mm

As we can see this is within the normal limits so we can happily go with &#$mm risers and

'/#mm going.

Example 2

%n this example we will take a Floor to Floor level of '1$$mm )!otal 2ise*.



%f we refer ack to the guidance we can use etween &#$mm and ''$mm as a riser.

!ake '$$mm as a riser )a nice round numer and not too shallow*. 3ow divide the total rise y

the suggested riser distance.

2"00mm / 200mm = 14

!his gives us &" risers at '$$mm



2eferring ack to the guidance we can have a going etween ''$ and +$$mm

4ets take '/#mm as a starting point.

!o check if this is ok we can carry out the 2R+G

2 200mm + 2!5mm = #!5mm

!his is within the range of ##$mm and /$$mm so we can assume this is acceptale.

!he image elow shows the finished stair. 3ote that the total run does not include step &".



How to work out the angle of the stair

-e can also work out the angle of the stair )as according to the guidance it can e a maximumof 42 $egrees*.

%n order to work out our stair angle we can use a it of asic trigonometry.

!otal rise 5 '1$$mm

Tot%l run (when wor&ing out the %ngle) = no o' risers going

!otal 2un 5 &" x '/#mm

!otal 2un 5 +1#$mm

T%n = pposite / $*%cent



So

6pposite Ad7acent 5

2"00 / 3"50 = 0!2

,n-erse T%ngent o' 0!2 =3# $egrees

Any outcome of 6pposite Ad7acent that is under $.8 will e under "' degrees.

!his was a it of a long post, ut hopefully it will e helpful when you come to working out your

stairs. %t does tend to e a it of trial and error, and of course is dependent on the space you have

in the uilding you are designing. %f you have any questions, or other ways of carrying out these

calculations, please write a comment elow. !hanks9

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How to Calculate Stairs