Staircase pitch. 42 degree pitch too steep?

[flanagaj]

So I am currently designing floor plans, and we are planning on having a floating staircase.  The ceiling height will be 2.4m and the expected height including the floor will be 2.7m.  If I do the trig calculation 2.7m / tan(42) I get 3m for the stair run. This works well, but it's the maximum pitch.  If I bring the pitch down to 35 degrees, I get a run of 3.9m.  The house is only 6.2m internal width, and the 35 degree pitch will likely mean that given the upstairs layout, it would fall foul of the minimum head height of 2.1m when walking up the stairs.   So cut a long story short, is 42 degrees ok, or do people feel that although it is fine from a building control point, it practically doesn't feel correct?

[Originaltwist]

I did a study on staircase design on https://originaltwist.com/2018/03/16/modern-floating-staircase/

 

Here's an extract that might help ... about the ratio for a 'comfort stair'

 

Tradition has it that a comfort stair is 7” x 11” for rise and going. Rounding up slightly that’s 180 x 280mm. B.S. regulations give ranges for rise of150 -220mm and 220-300mm for going G. The ratio of rise to going gives an important angle which here would be around 33 degrees and must not exceed 42 degrees. You’ll need this angle to saw off the ends of the beams.

The distance H between your two floor levels will set the rise. Find which whole number divides into H to give a rise R near to 180mm or what you prefer. That whole number is one more than the number of treads but note that the bottom tread might be a platform like the one on the sketch above.

Tread thickness T.  B.S. regs state that a 100mm ball must not pass between stairs or guards so if we say that the open gap between the treads will be 98mm then T = R – 98 or more.

The Going overlap. B.S. regs state that the overlap on open stairs must exceed 16mm but too much spoils the design, as you will see when you draw yours. So tread width W = G + 20 will do for a start.

So the treads will be something like 300 x 80 in section. As for length just bear in mind that stairs over a metre wide must have hand rails on both sides. I think 85cm looks about right.

Length of box beams L. To make life easy you could set the top of the box beam level with the top of the top tread, so; The base of our triangle is (no of treads -1) x G / R and then just use Pythagoras to get the longest length of box…. or, frankly, just draw it and see what you get. The drawing will reveal what angle to cut on the ends of the box beams too.

Make a note of all your numbers then make a drawing of the side elevation to scale. Sketchup is perfect for this and is free and easy to use. Note the intersection of the top of the angle iron, the beam and the back of the tread. N.B. Sketchup can repeat copies easily so draw and colour just one tread then copy it upwards by the rise and then across by multiples of the going.

[markc]

@Originaltwist great post, you just saved me a lot of typing regarding the importance of angle for the “feel” of a stairway while using. 😃

[joe90]

I used stair box to design mine and found their online design stuff easy to do.

[Bonner]

‘Other suppliers are available’ (Pears and TK for examples) all use similar tools. Saves doing the Math and gives you lots of detail including 2D & 3D images. I ended up with 39 degree pitch which was more than I wanted having failed to identify the constraints at design stage. Having said that, it feels ‘right’ now it’s finished.

[Russdl]

Ours is 36 degrees and feels right.

 

As @Originaltwist says, Sketchup is brilliant for this, you can endlessly play around until you’ve got what you like and what fits comfortably in the space available. I’ve probably got 50+ iterations of this staircase including 3d renders whilst I played around and finalised the design. 
 

I should have added, we have a second staircase going up to the loft, that one is 42 degrees (and not compliant due to a bit of a balls up by the architect - long story) anyway that staircase feels steep. 

 

 

Edited August 23 by Russdl
Added the last bit.

[Nick Laslett]

2 hours ago, flanagaj said:

 So cut a long story short, is 42 degrees ok, or do people feel that although it is fine from a building control point, it practically doesn't feel correct?

Mine are 40°. They are too steep for my liking. They’ve been in place since November 2022, so I’ve had plenty of opportunity to use them whilst working on the house. If you can I would definitely have a shallower angle. One of the hard to get right decisions, which are hard to undo. We have a poured concrete staircase. 

[flanagaj]

2 hours ago, Originaltwist said:

I did a study on staircase design on https://originaltwist.com/2018/03/16/modern-floating-staircase/

 

Here's an extract that might help ... about the ratio for a 'comfort stair'

 

Tradition has it that a comfort stair is 7” x 11” for rise and going. Rounding up slightly that’s 180 x 280mm. B.S. regulations give ranges for rise of150 -220mm and 220-300mm for going G. The ratio of rise to going gives an important angle which here would be around 33 degrees and must not exceed 42 degrees. You’ll need this angle to saw off the ends of the beams.

The distance H between your two floor levels will set the rise. Find which whole number divides into H to give a rise R near to 180mm or what you prefer. That whole number is one more than the number of treads but note that the bottom tread might be a platform like the one on the sketch above.

Tread thickness T.  B.S. regs state that a 100mm ball must not pass between stairs or guards so if we say that the open gap between the treads will be 98mm then T = R – 98 or more.

The Going overlap. B.S. regs state that the overlap on open stairs must exceed 16mm but too much spoils the design, as you will see when you draw yours. So tread width W = G + 20 will do for a start.

So the treads will be something like 300 x 80 in section. As for length just bear in mind that stairs over a metre wide must have hand rails on both sides. I think 85cm looks about right.

Length of box beams L. To make life easy you could set the top of the box beam level with the top of the top tread, so; The base of our triangle is (no of treads -1) x G / R and then just use Pythagoras to get the longest length of box…. or, frankly, just draw it and see what you get. The drawing will reveal what angle to cut on the ends of the box beams too.

Make a note of all your numbers then make a drawing of the side elevation to scale. Sketchup is perfect for this and is free and easy to use. Note the intersection of the top of the angle iron, the beam and the back of the tread. N.B. Sketchup can repeat copies easily so draw and colour just one tread then copy it upwards by the rise and then across by multiples of the going.

Aside from the treads hanging off the wall that design is exactly what I have planned.  The large concrete GFRC panels will be bolted to the wall with stainless bolts.  The panels are super easy to make, and I have made them before for our last house renovation.  Cheap as chips too, as you just need sand + cement + super plasticiser + alkaline resistant fibres..   If you have a lot to make, you simply buy liquid rubber mould solution and make a mould from a master tile that you have cast using a melamine mold.

[ProDave]

3 hours ago, flanagaj said:

The house is only 6.2m internal width, and the 35 degree pitch will likely mean that given the upstairs layout, it would fall foul of the minimum head height of 2.1m when walking up the stairs.

Our house is 7M deep so only a bit more than yours and especially if you are having room in roof or 1.5 storey, as you say you may get into head height issues.  For this sort of house a stair split into 2 with a half landing works well.  In our case up 6 stairs to the half landing, turn 180 degrees and up another 7 stairs and you arrive on the upstairs landing at almost the highest point of the roof structure and no worries whatsoever about head height.

 

I then took the available space we had, constrained by doorways downstairs and upstairs, and made the going as long as it could possibly be and I think we arrived at about 40 degrees.  All easy to do with the Stairbox on line tools and that is who supplied ours.

 

The challenge will be to design a two flight stair as a floating stair, I leave that for someone with more imagination than me.

[elite]

I'm just shy of 42 degrees, and if I wasn't constrained with it being a renovation and ceiling clearances etc I would have gone shallower. That said it doesn't feel wrong, just not as perfect as you would want in dream build

[ProDave]

Comfort in use is largely a case of what you are used to.

 

The going of our stairs is a lot more than the minimum. I can get my size 9's flat on the stairs entirely on the stair.  Contrast that to many older houses, built before modern building regs where the going of the very short stairs is only about 3/4 the length of my foot.  That now seems an insane design to me, but as a younger man used to stairs like that, I thought nothing of it.

[joe90]

1 hour ago, ProDave said:

a stair split into 2 with a half landing works well. 

 

[flanagaj]

I was trying to avoid a split staircase as I ideally want to have a nice open hallway as per our design below

[Dave Jones]

42 is very steep.

[flanagaj]

7 minutes ago, Dave Jones said:

42 is very steep.

I have manged to bring it down to just under 38 degrees.

[ProDave]

A straight stair ending near the back wall of the house is only an issue if like us you have room in roof with restricted eaves height.  I thought your plan has full height upstairs so you will have no problem at the top.  A compromise might be a quarter landing near the top, 90 degree turn for the last 2 steps?

[flanagaj]

26 minutes ago, ProDave said:

A compromise might be a quarter landing near the top, 90 degree turn for the last 2 steps?

That is a possibility

[Bonner]

5 hours ago, joe90 said:

 

👍 You can have a rest half way up

[ProDave]

10 minutes ago, Bonner said:

👍 You can have a rest half way up

Our stairs are just like that. And we have a nice tall window to look out of.  I often think a chair would go nicely there.......

[ETC]

Won’t comply.

[joe90]

51 minutes ago, ETC said:

Won’t comply.

What won’t?

[joe90]

1 hour ago, ProDave said:

Our stairs are just like that. And we have a nice tall window to look out of.  I often think a chair would go nicely there.......

I wanted to do that but having a conservatory outside meant the window had to go at upstairs height (long strings on the curtain pulls).