The Joy of Drafting by alan linklater S 1 basic terms size of hole cut out cut at line of intersection of headroom minimum line and soffit headroom line (min clearance) 3000 FLOOR TO FLOOR usable space 1500 clear 2000 clear nosing line low storage SECTION THROUGH headroom line wall 2000 clear 1000 min clear goings light arrow ALWAYS in the UP direction only, runs from bottom nosing to top nosing SECTION THROUGH nosing line handrail size varies but usually 30 dia or more PLAN of DIAGRAMMATIC SECTION RISERS range in height from 115 to 195 GOINGS range in width from 240 (residences) or 250 for all other building types to 355 riser going nosing line = line joining all nosings nosing = junction of going & riser
The Joy of Drafting by alan linklater S 2 stair layouts 4000 24 equal risers each 166.67 24 risers is illegal 4000 24 equal risers each 166.67 2 flights is legal any combination of riser numbers is fine but limited to 2 min & 18 maximum in any flight LANDING = 3 goings long any individual string of steps is a FLIGHT..NO LANDING..WITH LANDING 5750 2000 750 3500 PLANS of above IN-LINE S PLANS of above 3500 1000 2750 1000 flight ANGLED can be any angle landing flight 1000 flight flight landing 1000 1000 RETURN NOTE... FLIGHT DIMENSIONS are INDICATIVE ONLY the stair flight widths and landing returns are the minimum legal requirement in public buildings
The Joy of Drafting by alan linklater S 3 spiral stairs Draw edges of each step tread from numbered point to central pole Plot the back edges of each tread similarly to the front edges (below) Give each trea a depth of 30mm Railing is plotted by drawing lines 950 high above each nosing Connect the tops of these lines using either flexible curves or french curves 4180 4180 380 380 Start with GROUND line or LOOR line divide height into equal parallel lines to represent each riser Project lines up from each riser on plan to meet its corresponding tread location Make sure you work on 1 riser at a time and NUMBER each point to avoid getting confused with all the lines 5 4 3 2 1 full width of step 499 3 420 nosing-to-nosing 35 handrail 35 handrail central pole 2 35 handrail 1 landing area landing area 600 line of actual walking 2280 headroom here under 1500 2090 headroom here under 1500 1500 MINIMALIST 1500 dia with tapered landing Tapered landing allows either: a) an additional rise to increase headroom or MINIMALIST 1500 dia b) keep the 190 rise but widen each going another 19mm or c) keep the 2090 headroom but reduce each rise from 190 to 177 with square landing MINIMALIST 1500 dia FREEFORM CURVED S Any curved stair can be set up in both plan & elevation following this point-by-point method and projecting lines vertically from plan to elevation
A few notes about S..1 BASIC Geometry, Logic and Setout issues required for DESIGN by ALAN LINKLATER As you know, Stairs or ramps are required whenever there are (or ground levels) at different heights to each other and need to be connected. You may also be aware that the old stairs in terrace houses are dreadfully steep with small treads and high rises for each step. If you lived in such a house and were not familiar with the stair character, this could create a dangerous situation where users could easily lose footing or slip down the stair, possibly aided by the fright factor of seeing such steep (and apparently unsafe/dangerous) stair. OK, of course some stairs can be steep the ones used to get out of a building in an emergency for example but as stairs are meant for going up as well as down, it is the climb and its degree of difficulty that we, as designers, need to consider when including stairs in our designs. I am suggesting that the use and the users of the stair need to be considered particularly their age and possible disabilities. These could be heart conditions, just generally out-of-shape, age, physical impairment or just simply make it easy for the users to get up and down in a safe and not-tootaxing manner. DESIGN To design any stair you ALWAYS start with a SECTION THROUGH THE. To draw the plan is fine but will not tell you how many steps you will actually need! The following notes will outline some of the BASIC issues relating to the logic and legality of the stair components requirements and a method of calculating stair rise which then gives the information to draw the plan last. To get a thorough understanding of ALL the requirements, I insist you read all of Part D of the BCA and write down each issue as it relates to your stair situation so you don t miss any legal requirement. STEEP S In exit stairs mentioned above, the major purpose of the stair is to get people down in a hurry during emergencies. These people are usually new to the building and may not be familiar with the geometry of the stairs so a safe stair design is required. Minimum standards for these safe stairs can be found in the Building Code of Australia (BCA) vol 1 in Part D, clause D2.13 Goings & Risers. Here, a range of acceptable (legal) sizes is given for treads (GOINGS) and steps (RISERS). RISERS can range from 115 min to 190 max and GOINGS can range from 240 (private houses)/250 (all other buildings)min to 355 max. See further notes on stair workings and calculations. EXERCISE 1 I heartily recommend that for the next stair you use, decide if it is gentle, easy or hard work..steep then measure the rise and going so you KNOW how a stair such as this would be notes by Alan Linklater 2009 1
affecting your clients. Now compare this with at least 4 other stairs to gauge dimensions used and degree of comfort in using the stair remember you are young and healthy and not all others are so fortunate. GENTLER S Aged people and children are suited to the 115 to 150 max range while us able-bodieds can handle 150 to 175 range without too much puffing at the top. In houses of at least 2 levels, walking between the various levels can involve many climbings of the stair during the day and although this may avoid the need for gym membership, this may create fatigue and unpleasant thoughts of the designer in mind of the user so careful choices are needed here in the geometry of the stair. Once again, load up your memory with the measurements and your reactions to the various (and numerous) stairs you have encountered so you KNOW an appropriate design size to use. Of course, if SPACE is a critical issue then your clients need to be informed of the resulting, more difficult stair than they were expecting and possibly show them an example to test out for themselves. GOINGS Goings are also within an acceptable range as listed in the BCA vol 1 in Part D, clause D2.13 Goings & Risers. The minimum width of a going is 240 in single houses and 250 for all other buildings to ensure your foot will fit on it safely. The maximum going is 355 which is ceremonial style stair and rarely used. RATIOS The combination of a rise and a going will give each stair its unique slope. The effort to climb this slope is similar to gears in your car where steep hills need low gears to enable your energy to be suited to the rate of climb while a flatter road can handle the top gears easily as the energy needed is far less. Accordingly, a high rise and narrow going will give a steep stair which can be softened by a) commonly reducing the rise or b) increasing the going. The BCA has a range of ratios for stairs as in the formula 2R + G = 550 to 700 (found in Table D2.13 of the BCA) where R is the chosen rise and G the going. Almost any combination of R & G meets this formula but I suggest you do some quick maths to couple the 115 rise and 355 going as well as the 190 rise and 250 going to see if they actually DO fit the formula for a legal stair. EXERCISE 2 DRAW 4 stair profiles with 4 different rise and going combinations and check the angle of the stair climb rate by using your adjustable set square and drawing a line touching the nosings (junction of rise and going at the front of the stair). Draw at least 5 rises in each. CALCULATING GEOMETRY for your DESIGN Stairs go from -to- (not -to-ceiling, so ensure you are using the correct overall dimension here) eg 3750 ground to first. 1 Select your chosen Rise value (between 115 and 190) to suit your clients needs, say 160. 2 Divide the -to- dimension by your R notes by Alan Linklater 2009 2
eg 3750 / 160 = 23.44 You can have only whole numbers not fractions of a rise so you will have either a) 23 rises or b) 24 3 The decision here is if you choose a) 23, the rise will be a little steeper than the 160 you selected, in this case 163.04 which is marginal or if you choose b) 24, the rise will be gentler, in this case 156.25. In either case, the chosen stair climb rate will not really be significant so either is acceptable. 4 However, the space used by an extra going may be critical and so the final design choice will rest on this. WIDTH Again the BCA tells us that for all buildings other than single occupancy dwellings (houses and the internal stairs of 2-storeyed apartments) must comply with the minimum stair widths. The minimum CLEAR width between wall and railing is to be 1000 with handrails added on to this. Check the BCA Part D, clause D2.9 Width of Stairways for the full story on stair widths. Stair railings can be min 30 diameter with a minimum of 50mm clearance between the rail and any wall to allow for fingers. This means a standard width of the stair structure is around 1100 if the stair is between walls with a railing on 1 side only. If your stair is wall-one-side and open on the other, the railing can either be set into the stair (requiring a stair width of 1100 min) or bolted to the side of the stair and the stair can be 1000 in this case. In houses, narrower stairs can be installed but consider how large furniture items will be moved between s when the house is being occupied and whether the narrow stair will really work. RAILINGS & BALUSTRADES These are described in detail in clause D2.16 Balustrades or Other Barriers as well as D2.17 Handrails and wire-type railings are also discussed. Generally, railings (or balustrades) to stairs must be a min height of 865 measured above the line of the nosings or landings for most buildings. Where the height of potential fall is great and the railing is serving a /landing 4m above the below, railings and balustrades are increased to 1000 high. In all cases, the elements making up the balustrade or railing must not leave spaces between which will allow a 125mm ball to pass through. Clause D2.16 describes these in detail. HEADROOM The minimum BCA clearance on stairways is 2000 measured vertically above a line connecting the stair nosings. Stair NOSING is the projecting point of each step where the going meets the riser. This line of nosings shows the grade of the stair. It is used to offset below the stair for the stair construction thickness. It is used above the stair for the line of the handrail as well as the required headroom. notes by Alan Linklater 2009 3
This 2000 clearance is fine as a minimum standard but can be disconcertingly low as you descend the stair. Also large furniture is hard to carry up such low-ceilinged stairs. To decide where the extent of the required headroom creates a hole in the, you need to: 1 Draw a section through the stair after first drawing the lines of course. 2 Draw a line through the nosings 3 Copy this line vertically by 2000 (or more as you see appropriate) 4 Draw the thickness in the upper 5 Where the headroom line cutes the ceiling of the above, this is generally the end of the hole in the and can be measured. You cannot guess the extent of this hole from a plan alone.you need the section in ALL stair designs. Did you notice that the number of goings in the stair = R-1? In commercial spaces where area rental is most valuable, you may choose to a) increase the R, or b) decrease the G down to the minimum or c) reduce the headroom down closer to the minimum. From this section, you can also see how much space is available to use UNDER the stair for storage, toilets etc. You cannot do this by plan alone either. HOWEVER clause D2.8 of the BCA describes what needs to be provided to safely fire-rate the stair if this type of storage is proposed. You can see that an efficient stair design is very fluid, needing fine tuning in the sizes of the members. This can only be done once you have drawn the plan and section and you may need to re-calculate the R and number of risers as well if you increase the size of the R. This of course reduces the number of goings and thereby can also shorten the required headroom hole size giving more area for rental. LENGTHS OF S The BCA limits the number of goings to between a minimum of 2 and a maximum of 18. One rise is simply a trip hazard as the eye does not readily notice the level change. 2 rises becomes noticeable and is the min number you can have in any flight. 18 risers appears too long when standing at the top and actually dangerous if people fall down the stair during a panic escape. FLIGHTS & LANDINGS A single run of risers in one direction is a FLIGHT of stairs. A flight runs between s or between and landing or landing to landing depending on the number of flights your stair requires. The stair is the sum group of the flights and landings. At the top and bottom of each stair is the served. If you have more than 18 risers required between s, you must break up the stair into 2 separate flights with a LANDING joining them. You can combine stair flights in the following arrangements: straight run, angled and return flights (flights either at 90 degrees or 180 degrees), all separated by landings. notes by Alan Linklater 2009 4
The landing is a minimum of 750 in length and must be the same clear 1000 width as the stair flights. Clause D2.14 talks about Landings and should be read to understand the full picture including a 1:50 slope allowance on landings if necessary. SPIRAL S Because most people have a phobia about dangerous spiral stairs and many fall or trip using them, the BCA declares them illegal so don t use them in public buildings unless they are not required for essential exits. I believe they can be used in single dwellings such as private houses and 2-storeyed apartments. A minimum size of 1500 dia is the absolute minimum in my opinion to be comfortably workable. Spiral stairs generally require about 11 to 12 rises to get required headroom underneath and to draw one, you need to know this. EXERCISE 3 Remember your challenge to prove me wrong by measuring whichever spiral stairs you can and making a personal assessment on the functionality. The BCA does show the geometry for a tapered going which if you put them together, you get a wide, circling stair just like the one from the airport control tower at Sydney Airport (see from General Holmes Drive near the runway overpass). This requires a ridiculous amount of space and so generally not an option, however, never say never and a use for a stair of this shape may be what is needed for your design effect. Further Notes There are further notes and exercises currently under construction on stairs and a cross-reference to these will be added here when completed. ALAN LINKLATER notes by Alan Linklater 2009 5