# Forum Home Renovation Stairs, Steps and Ramps  Advice on riser problem please

## alpina

Hi all, 
I have the following problem with my new stairway design ... 
The main stairway proposed has a total of 24 & 19 risers in the flights from ground to 1st and 1st to 2nd floors respectively. The BCA only permits a maximum of 18 risers per flight. And with a maximum gap of 125mm having to be maintained between stair treads, it limits the adjustment that may be needed to reduce the riser numbers. 
Any advice on how I can overcome this obstacle? 
Thanks in advance. 
B

----------


## commodorenut

Can you lower the current landing a step, and add another landing 5 steps from the top?
(or vice-versa - add 5 steps to the bottom, a small landing (even a 90 degree turn if space won't allow a straight run) then have 2 x 18 steps?)

----------


## Gaza

> Hi all,
> And with a maximum gap of 125mm having to be maintained between stair treads 
> B

  the riser height can be upto 195mm, depending on the tread width. 
if you went with a 290mm tread a riser height of 185mm would comply. 
the 125mm rule is for open treads with no riser to get over that you could put a strip of timber on the nosing of the tread to build the thickness up.

----------


## ringtail

Max rise is 190 mm OR 220 mm for spiral stairs. Min go is 240, Max 355 OR 210/370 for spirals and the slope relationship ( 2 rise + go) is Min 550 Max 700 OR 590 / 680 for spirals. 
Can you give the heights please

----------


## alpina

Thanks for responses guys. 
The design that I had in mind was a steel beam running through the centre with cantilivered stairs being supported off it. Ideally, I was not looking at using risers as I wanted to see through it. Having said that if visible risers is the only solution it's no biggie and I can get away with putting a mirror finish on the risers to get a similar effect. 
Not sure if it makes a difference, but this is for a commercial application.  
One side of stairs (right side) will have a brick wall and the other side (left side) will be vertical steel cabling. I'm assuming that handrails will be required on both sides. Stair width (excluding handrails) will be 1mt and I'm not sure what the minimum I have to allow for the handrails? 
Stair height from ground floor to level 1 will be approx 4325 and from level 1 to level 3325. 
Really appreciate your help and hope that this information makes things a little clearer. 
Cheers, 
B

----------


## Gaza

you dont need a full riser just a strip of steel or something to reduce that gap,

----------


## ringtail

Ok, from calculations you will need 
for the first flight - rise of 173 mm = 25 rises and 24 treads 
for the second flight - rises of 175 mm = 19 rises and 18 treads. 
Given that you will need a landing for both flights, I would drop the rise down to 166 mm giving 26 rises and 20 rises respectively. A smaller rise is Much more comfortable anyway and you wont have any drama with leaving the stairs see through :Wink:

----------


## alpina

> Ok, from calculations you will need 
> for the first flight - rise of 173 mm = 25 rises and 24 treads 
> for the second flight - rises of 175 mm = 19 rises and 18 treads. 
> Given that you will need a landing for both flights, I would drop the rise down to 166 mm giving 26 rises and 20 rises respectively. A smaller rise is Much more comfortable anyway and you wont have any drama with leaving the stairs see through

  Sorry to be a pain ringtail, but if i go this way (which may be the only way), what would be the size of the landing on each floor (eg, 1mt wide * ?), would I place the landing at the midpoint and what would be the total length of such a stairwell from bottom to top? 
Thanks again. 
B

----------


## ringtail

The landing must be the same width as the staircase with a minimun go ( length of 750 mm). So the general rule is to allow 300 mm for every rise, so if you went for the smaller rise of 166 mm you would have to allow 25 x 300 (7500) + the landing so about 8500 of stringer length for the first flight. The second would be 19 x 300 (5700) + landing so about 6700 of stringer length. For the actual measurement of the go of each flight assuming you are using a tread of 250 mm and a landing that is 750 mm it would be 24 x 250 (6000) + 750 = 6750 and 18 x 250 ( 4500 ) + 750 = 5250. This is how far each flight would project horizontally from its fixing point at the top. 
As far as where to put the landing - midway is best visually and practically.

----------

