Staircase problem and BCA

Hi All

I have a problem that I need some feedback on. I am building a staircase to connect the main part of the house with some newly created space underneath (have put two new bedrooms down there).

Before I go into detail, we have no intention of moving for some time so this is all "internal work" that the council doesnt need to know about, it was here when we moved in (your honour).

My problem is a lack of space to fit the staircase to the BCA requirements. The staircase is two short straight flights (6 rises) with a 180 degree landing. All to be built out of reclaimed timber, 265x42mm dressed hardwood. In the space I have, I have the option of 6 rises of 196mm each (260mm going) or 7 goings of 214mm each (168mm rise). One is a slightly over high (BCA max 190mm) rise, the other is a too short (min 240mm) going.

I dont have a lot of time to build it (17 days off work to do a heap of work, this staircase plus the last 10% of a lot of other jobs for SWMBO). It is also my first staircase so dont particularly want to get into the complications of winders. I also dont have any spare timber to allow me to stuff up. In the US, the maximum stair rise appears to be between 7 3/4 inches (196mm) and 8 1/4 inches (210mm) depending on your state so my staircase of 196mm rise is not too outrageous (unless you are a council inspector). The ratio of rise to run and the angle of each flight (37 degrees) is within limits.

Does anyone have any thoughts on options here? There is just not enough room to adjust the staircase into the regs without losing landing width (it is only 900mm top and bottom so there is not much to play with). We dont need to move anything other than people and maybe a basket of washing up and down, there is walk in direct access to both levels (on a slope) so dont need to factor in moving furniture.

I have a total hole in the floor of 3100x1600mm (between the structural steel RSJ's and walls but I need 900mm to walk past the entrance at the top so 2200x1600mm to build in) and have to drop 2350mm. It is going to be narrow but I should be able to keep it above the 750mm minimum width.

Fun and games.

Ben

As an inspector I would make sure the stairs are right, if someone trips and breaks a leg (or worse) your insurance could find an outclause to pay up. Many claims on building inspectors and homeowners involve stairs, if you dont have a permit thats will not look good. The only time the stair requirments can be altered is when they lead to storage areas, then AS 1657 can be used.

How about a couple of winders at the bottom of the stairs that turn 90 degrees.

Even though your are staying a while when you go to sell in say 10-15 years time it could become an issue with any purchasers that have a building inspection done.

If you want to be inside the BCA requirements there is no easy way.

While I can put the landing slightly higher to bring the top flight back to standards, I then have issues with the lower flight. Due to the going requirements, I dont have the length to put another step in. In reality, I have a 1300mm run for each flight. The bottom of the stairs finishes on a raised platform so you dont have to step up again to go out the back door but its height cannot be changed due to the concrete foundations it is hiding. Longer term plans are to cut a hole through the back wall in front of where the stair ends, we are enclosing a walkway to the laundry so dont want to put winders in which will make the bottom of the stairs very awkward.

The other option is to put a single step in the middle of the landing making two square 90 degree landings with a single step between them but I thought the BCA required a minimum of 3 steps. Is this an option?

Regards
Ben

It says you must have a mimimum of 2 risers.

I guess I am screwed then, I either run the gauntlet or have to build a winder. Perhaps a square landing at the bottom of the top flight then a 90 degree winder onto the bottom flight from the landing to give the finishing direction I need at the bottom.

What a pain in the freckle. I really didnt want to have to make winders.

Regards
Ben

Maybe if you talk to a council inspector (with no names or addresses) they could give you another solution, or at least what they would be prepared to accept and certify.

If i'm reading your post correctly as to your layout you can split the landing with a single step as long as both landings are a min. of 750 mm.
The 'step' is not a part of the 2 separate flights. It is merely a change in levels. Min. 115 & max. 190 but should be kept uniform with the risers on the flights.

Christopher Alexander of http://www.patternlanguage.com/ comments on stair proportions, based on an analysis of vernacular designs in many cultures. He says that so long as the tread plus riser dimension is 17.5 inches, it doesn't really matter what the distribution is between them. That is, you could have a 10 inch tread, and 7.5 inch riser, or you could have a 7.5 inch tread and 10 inch riser. Doesn't matter. Obviously, the steeper stairs become more like a ladder.

Worth having a look at his site.

Hi Peter

That is exactly what I want to do if I cannot have over height rises, two straight flights of 6 steps meeting at a landing with split in the middle the same height as the stair rises. They will be 800x900mm each. If I do that I will be able to meet the BCA size requirements for the rise/run and will have all rises evenly spaced at 181mm top to bottom (including the landing split) which is good. It is also more right angles, not a triangular tread in sight. I was not sure if I was allowed to do that.

I have the BCA at home, do you know the clause I need to look at?

Regards
Ben

landings are covered under BCA Volume 2, Section 3, Part 3.1.9

Thanks

Much appreciated

Ben

Quote:

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Originally Posted by Wildman

One is a slightly over high (BCA max 190mm) rise, the other is a too short (min 240mm) going.

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Hi Guys,
I am currently installing a set of stairs with metal stringers. It will have merbua treads.
Can you please explain these measurements to me?
is there a min/max gap allowed between the treads and is there a min/max height allowed from tread surface to tread surface?

If the stairs are over 1M high, or if it is possible to fall 1M or more from them, there must not be any gaps in the stairs or balustrading through which a 125mm sphere can pass. The min/max tread height is not quite as simple as it is tied to the width of the treads. Sorry, haven't got my BCA handy, hopefully someone else will enlighten you.

Mick

Quote:

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Originally Posted by dan76n

Hi Guys,
I am currently installing a set of stairs with metal stringers. It will have merbua treads.
Can you please explain these measurements to me?
is there a min/max gap allowed between the treads and is there a min/max height allowed from tread surface to tread surface?

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Yes, a daylight in excess of 125mm from top of tread to underside of next tread is illegal. If you have say a rising of 150mm , your tread will need to be in excess of 25mm finished thickness.

Treads must be between 355mm -240mm
Risers must be between 190mm-115mm
Riser x2 + Tread must be between 700mm and 550mm

Balustrading must be 1000mm high (min)
On a stair it is 860mm measured vertically from the line of the run of the nosings (min)
You are allowed a 500mm transitional zone between the 860 and 1000
Design not to allow a 125mm to pass through .
Allow for deflection in above ...refer to ASA 1180
Glass infill to comply with ASA 1288-2006
If difference between FFL and natural ground level or floors is in excess of 4.0m you are not allowed a horizontal or near horizontal member between 150mm and 760mm from FFL.
Wire assemblies to comply with the relevant BCA in place at determination of your DA.


Hope this helps

Brett