baluster spacing from first principles. How?

[dirtydeeds]

i know how to calculate bluster spacing

and i dont

sometimes it works and sometimes it doesnt. we know the spacing between balusters and the dimensions of balusters

divide the gap between the newels by the centre to centre spacing of the balusters and round up

it works

BUT only sometimes

sometimes you need to add another baluster to get the spacing right




as you can see i need help. however i dont want a calculator, i want the first principle calculation

can anybody help

[dirtydeeds]

i know that it is possible to do it by rule of thumb, ie two balusters per step but that does not ALWAYS work either and in this case i dont know the number of steps

i know the problem in my calculation is that the centre to centre measurement does not allow for the fact that there is one less baluster than space

[9fingers]

Add the maximum inter-baluster spacing to the width of the baluster and divide that into the distance between the newel. Round the result down to the nearest integer and that is the number of balusters


Eg 100mm max gap, 25mm baluster and 5018mm between newel posts

5018/9100+25) =40.144. round down to 40.

test the answer

40 balusters at 25mm =1000mm, leaving 4018mm for the 41 gaps
Gap =4018/41 =98mm ie less than 100mm

Is this what you need DD??

HTH

Bob

[dirtydeeds]

9F

thats where everything goes right OR wrong

it seems to work on some newel distances others it doesnt




hence my question

[jfc]

I gave up trying to work it out years ago , i just start nicking or adding mm when i get half way up .

[sainty]

9finger said:

Eg 100mm max gap, 25mm baluster and 5018mm between newel posts

5018/9100+25) =40.144. round down to 40.

I think that you meant

5018/ (100+25)) =40.144. round down to 40.

Just to be pedantic!!!


Rgds

Sainty

[sainty]

Just to clarify. All these dimensions need to be taken in the same plane, ie if you measure down the stringer you must also measure the balusters are the same angle. Also the 100mm is the maximum spacing which in the case of vertical balusters is a horizontal measurement so that would involve too much trigonometry for 22.19 on a Tuesday night!

That makes sense to me anyway!


rgds


Sainty

[engineerone]

surely if you are going up stairs, then the width of the stair itself may well vary as you go up, so that is why it doesn't seem to work all the time.

having never done it i can feel sympathy with you all. the maths is always the same, but part of what you have to consider is the aesthetics. although you can see a 1/8th droop in a shelf, it seems to me from various amounts of looking at balusters is that you would find it much more difficult to notice the distance cause you rarely stand and look at them from a level viewpoint.

surely the most important thing is the distance from the bullnose, and then making it look similar on each succeeding step.

if however you are talking about balusters that do not touch the
stairs but is rather what we call a bannister, then you revert to the original maths.

paul

[andy]

But you always have one more spacing than number of spindles therefore you should subs tract one spindle thickness from the overall distance between the newel posts and then divide by the 100mm plus thickness of the spindle


((5018-25)/ (100+25)) =39.944 round up to 40.

therefore

((5018-25)/40)-25=99.8mm (spacing)


Sorry DD but its the only way I know how to calculate it but this might be useful

[jfc]

Or just start fitting them and lose a mm per gap when you get close to the top

[9fingers]

dirtydeeds said:

9F

thats where everything goes right OR wrong

it seems to work on some newel distances others it doesnt




hence my question

OK DD can you give me a specifc set of figures where that does not work?

I just plucked my numbers out of the air to illustrate the formula.

Yes you are correct Sainty the '9' should have been'(' . A simple slip of the shift key.


Andy: your formula is wrong

41 spaces of 99.8mm plus 40 ballusters at 25mm means a space of 5091.8mm between Newel posts not 5018 that we started with.

Bob

[andy]

9finger said:

Andy: your formula is wrong

41 spaces of 99.8mm plus 40 ballusters at 25mm means a space of 5091.8mm between Newel posts not 5018 that we started with.

Bob

Thats a BIG yes Bob given you a karma point for that one


modified formula

((5018-25)/ (100+25)) =39.944 round up to 40.

therefore

(5018+25 (additional spindle)) /41(spaces)-25(spindle thickness)=98mm(spacing)

(5018+25)/41-25=98mm

Andy who must try harder ;D

[9fingers]

No Stress Andy!

We are all learning this together. Some we win some we lose and I made a mistake in my original formula too.

BTW Thanks for the KP ;D

Bob

[dirtydeeds]

ive cracked it for raised string staircases, with two layouts

you need two baseline lengths, one for calculating the baluster centres and one for calculating the gaps.

one is measured between the newels, the other is the addition or deduction of one baluster to this first length.

if you go with the standard layout you add a virtual balluster to the newel to newel length for calculating the centres of the balusters and the newel to newel length to calculate the gaps

if you go for a half baluster attached to each newel post you use the newel to newel for the cnetre spacing and dedut one baluster to calculate the gaps



these calculations without the staircase angles will also work for spacings for the landing balusters and for picket fences

modified slightly they work for both equalised and modular joist spacing

[9fingers]

DD,

Before I saw your last post, I knocked up a simple excel calculator which I hope might help you.

You can try it here homepage.ntlworld.com/bob.minchin/W-UK%20Folder/BalusterCalc.xls

I hope it helps.

Bob

[argus]

.

Not really my field, but if they are for stairs etc., I think that there are minimum separation distances for spindles and the like in the building regs somewhere..... prevents little Johnny from either climbing through or sticking his head through....


.

[dirtydeeds]

9 fingers i stopped updating at excel 97 so excel 8 is now beyond my computer

argus you are right the building regs. in domestic settings the essential information is

that the handrail must be a minimum of 900 above the nosing and a 100mm ball must not pass anywhere through a staircase and the minimum steps and risers means that the steepest staircase is 42 degrees

almost all staircases built at 42 degrees to take up the minimum possible space

our building regs do not have any minimum widths


so the 100mm rule means fully open risers are out, you need stub risers

most balusters are turned so the spacings are less than 100mm if they arnt square

on landings the baluster spacing tends to be about 80mm because all the turnings are in the same horizontal plane

on the stairs the spacings for the same balusters are around 89mm because the turnings are not in the same horizontal plane


the 80 and 89mm spacings are for Richard Burbidge turnings, other manufacturers may have different dimensions but dont expect massive differences

[9fingers]

DD:
I've posted an excel 97 version here
homepage.ntlworld.com/bob.minchin/W-UK%20Folder/BalusterCalc97.xls

Bob

[dirtydeeds]

bob9

thanks for putting so much effort into this for me but i got the following message


the page cannot be found

The page you are looking for might have been removed, had its name changed, or is temporarily unavailable.

[9fingers]

Sorry about that DD.

I have fixed the link - it had a spurious dot on the end.

I hope it now works for you.

Bob

[tim]

a 100mm ball must not pass anywhere through a staircase

Not a baluster specific question (apologies) but I am about to change the balusters and handrails for our staircase. They are currently 70's ranch style post and rail - nice. However, the staircase is open riser with greater than 100mm rise. Can I change the balusters and leave the treads as is and not contravene regs?

Cheers

Tim

[9fingers]

Tim, I've not looked at the very latest regs but generally there is a principle of 'change of use'If the work you are doing is not related to increased traffic up & down the stairs, then you don't have to comply with the latest regs - I'm sure you are not allowed to make it worse than it was when you started.
If however you were for example putting on an extension and making more bedrooms upstairs, then the BCO would be likely to insist that this was a change of use for the staircase, and want it brought up to the latest regs.

Best way as always is to talk to the BCO - the are generally quite helpful - as least round here anyway.

Good Luck

Bob