Safety is Paramount when it comes to Stairways-Part M
It stands to reason that stairways must be safe. If stairs are too steep, and they don’t have railings, or if screens and balustrades are not strong and secure, people may fall with disastrous consequences.
What the National Building Regulations say about Stairs and Stairways
“Any stairway, including any wall, screen, railing or balustrade to such stairway, shall:
(a) be capable of safely sustaining any actions which can reasonably be expected to occur and in such a manner that any local damage (including cracking) or deformation do not compromise its functioning;
(b) permit safe movement of persons from floor to floor; and
(c) have dimensions appropriate to its use.”
What this means is that stairways, in addition to all the elements relating to them, must be properly designed. This takes us back to Part B of the NBR, which deals with structural design.
Like everything else, stairways must be designed to provide the strength, stability, serviceability and durability required for use. It is imperative that they are built so that any accidental overload won’t cause the stairway to collapse. It is also vital to takes steps to ensure that people won’t fall off the structure. If the sides of the stairs don’t have railings or screens this CAN happen – and it does (sadly) happen.
In addition to these general requirements, there are fire requirements that must be adhered to. These are outlined in Part T of SANS 10400 – Fire Protection, but when it comes to houses, those that are relevant mainly relate to basics (including the materials used to build your home). For instance you don’t have to have fire escapes, exit doors, escape routes, and that kind of thing.
SANS 10400 Stairways – Part M
As always, the South African National Standards give a good rundown on how we should build to ensure that we “satisfy” the legislation. The most recent Standard was published in April 2011; and it contains new guidelines that relate to both masonry stairways and timber stairways.
You will find Part M of the legislation towards the end of Standard, on Page 11.
It should be read in conjunction with several other Standards, including SANS 2001-CC1, -CC2, and -CM1 that deal with structural concrete works, minor concrete works and masonry walling; SANS 1460, Laminated timber (glulam); and SANS 1783-2, that deals with stress-graded structural timber and timber for frame wall construction; as well as several other parts of SANS 10400, specifically Part A (general principles), Part B (structural design), Part K (walls), Part S (facilities for people with disabilities), and Part T (fire protection). This is important because, for instance:
- Part S reduces the rise of the step (as indicated in this part), increases the width of stairways and the length of landings. It also has a requirement that solid risers should be used where stairs overlap the next lower tread, and another that specifies the need for handrails on both sides of the stairway.
- Part T increases the standard width of stairways as indicated in this part, disallows the use of spiral stairways, and requires solid risers for all buildings except those defined in Part A as D4 (a plant room that contains mechanical or electrical services that are necessary for the running of a building, and are usually left unattended).
Requirements of this particular Standard that relate to dimensions specify that:
- there must be sufficient headroom above any stairway: at least 2,1 m measured vertically from the pitch line of the staircase (see drawing below)
- stairs need to be wide enough for safe use, usually not less than 750 mm (see drawing below)
- the going (depth of the tread) and width of treads must be at least 250 mm (see drawing below)
- treads of stairways that do not have solid risers must overlap the next tread by at least 25 mm (see drawing above)
- landings serving two flights in a straight line need to be at least 900 mm long and at least as wide as the flight of stairs
- there shouldn’t be a vertical rise that is greater than 3 m between landings
- single step risers shouldn’t be more than 200 mm
- doors cannot open onto stairways unless it’s onto a landing – and the landing then needs to be at least the width of the door (which must not obstruct people using the stairs)
Sometimes the dimensions of risers and going of treads vary in a flight of stairs. This variation should not be more than 6 mm. Further, dimensions of each individual step can be checked for safety by adding the dimension of the going to 2 x the height of the riser. This should be at least 570 mm and no more than 650 mm.
Tapered treads and winders (which are are steps that are narrower on one side than the other and used to change direction of the stairs without landings) are most common in spiral stairways. If they don’t form part of a spiral staircase, they must be designed to comply with the minimum tread and riser dimensions shown in the drawing above, and have a minimum going of 125 mm. The angle between successive risers (measured horizontally) must be constant (see drawing below).
Stairways that incorporate winders – defined by the SANS as a “tapered tread that has a going of at least 50 mm and which is used in conjunction with non-tapered treads in a single flight” – are permitted in our homes as long as there are no more than three of them, and the winder may not turn through more than 90 degrees.
Spiral stairways are defined as a “succession of tapered treads forming a curved stairway which extends as a single flight from one floor or landing to another”. These must be no wider than 800 mm and may not be used as an emergency route. There are also restrictions in terms of certain buildings where they may not be used, including theatres and other entertainment venues, schools, sports facilities, places of worship, exhibition bass, jails, hospitals and health care facilities, offices, hotels, dormitories and hospitality venues.
Prevention Against Falling
It should be common sense, but people don’t always see it that way, because stairs don’t always LOOK good with railings!
Essentially what SANS tell us is that:
If a flight of stairs is more than three risers high, it could be dangerous, especially if toddlers and old people use it. This is why it is essential to have some sort of protection to prevent falling.
This can be in the form of:
- a secure wall
- a screen of some sort
- railings or a balustrade – all of which should be at least 1 m high
Other issues include “openings”. If a child can fall through a gap in the railings, or if someone falls and their leg or foot gets stuck in the gap, it could end up really badly. The opening specification is similar to that which relates to swimming pool fencing: it shouldn’t allow anything with more than a 100 mm diameter to pass through it.
Handrails are also an important element. If a flight of steps continues for more than about five risers, there should be a handrail of some sort. And any sort of handrail MUST be securely fixed to the wall, screen, railing, balustrade or whatever! In some instances, for example when the stairs are wide (more than 1,1 m), it might be necessary to have a railing on either side.
If a screen is made of glass, it is vital that the glass used complies with the relevant SANS.
There are several clauses that relate specifically to timber stairs in SANS 10400 Part M (Edition 3, 2011). This section was previously not covered in the “deemed to satisfy” regulations.
Stringer beams support treads, and where these are not be wider than 1,2 m in double- and single-storey domestic residences and dwelling houses, they should be at least 48 mm x 225 mm. Grade 5 timber should be used and it should not be excessively warped.
These must be at least 36 mm thick. Since timber stairways are designed in different ways, the options are that they may be:
- built into masonry walls with a minimum end bearing of 90 mm
- supported on a steel angle cleat that has minimum dimensions of 50 mm x 50 mm x 4 mm
- bolted to a wall with two masonry anchors per clear according to the manufacturer’s instructions
If anchors are used and embedded into a Grade 20 concrete (which will be 20 MPa), these anchors must have “a safe working load in sheer of not less than 1,25 kN, certified by the manufacturer”.
Materials Used for Timber Steps
Building Materials and Tests in general are covered in Part A of the National Building Regulations. In terms of timber, it should be treated against termites and wood borer as well as protected against fungal decay in terms of SANS 10005. For consumers, the important thing to look for is the product certification mark of a body that has been certified by the SA National Accreditation System.