Condo glass CBC News
Nil Koksal reports 3.14 video report
11 June 2016
A Toronto condo developer says it will replace all the balcony glass in three of its buildings.
More condo balconies are having the glass replaced after panels have
shattered.
Notice how the CBC video report does not give the address of the two
buildings, just the street corner.
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A guide to glass balcony guards and breakage
Condo Business
By Dale Kerr
07 June 2016
Over the past several years, there have been many instances of glass balcony guards breaking.
All glass breaks, but different types of glass break more or less
easily. The type of glass typically used in windows, for example, is
annealed glass, which is the weakest type of glass. When annealed glass
breaks, it breaks into long sharp shards. This can create a dangerous
situation if, for example, such glass is used in a door that someone
might push their hand through.
Glass can be made stronger through a process known as heat treating. In
this process, annealed glass is heated to about 700 degrees Celsius,
then rapidly cooled, or “quenched”. The glass surfaces cool at a faster
rate than the interior of the glass, which creates a compression zone
on the face of the glass and a tension zone inside the glass. This
makes the glass more resistant to breakage.
There are two types of heat-treated glass: heat strengthened and
tempered. Heat-strengthened glass is about twice as strong as annealed
glass, whereas tempered glass is four to six times as strong as
annealed glass. The difference between heat-strengthened and tempered
glass is the rate at which the glass is cooled. The faster cooling of
tempered glass results in a stronger compressive surface, improving its
strength, but it also results in more tension in the glass.
In situations where injury due to breakage is a concern, tempered glass
is typically used. Because of the stresses in the glass, when tempered
glass breaks, it breaks into tiny crystals with relatively blunt edges
that are far less likely to cause injury. For this reason, and
because of its improved strength, tempered glass is used for balcony
guards.
Over the past 20 years or so, glass balcony guards have become more
common. Glass is architecturally appealing and allows an unimpeded view
from a balcony, unlike panel or picket balcony guards. Glass is also
relatively inexpensive, it doesn’t corrode and it requires little
maintenance, unlike metal guards that require regular painting.
As balcony lengths have increased, the size of the glass panels used on
balconies has also increased. Not only has the length and height
of glass balcony guards increased; the thickness of the glass has also
increased to enable the glass guards to resist the increased loads from
wind and potential impacts.
So why have glass balcony guards been breaking?
Nickel sulphide inclusions
One of the possible causes of such glass breakage is a nickel sulphide
inclusion. Sulphur is used in the glass-manufacturing process to help
eliminate bubbles. Glass can be contaminated by nickel being introduced
into the glass-manufacturing process in the raw materials, during
handling and storage, or from the fire brick in the furnaces. A single
gram of nickel can contaminate thousands of tonnes of glass.
At high temperatures, such as those encountered during heat treating,
the nickel sulphide particle is smaller than it is at lower
temperatures. Due to the rapid cooling required to manufacture tempered
glass, the particle can be trapped at the smaller size. Over a period
of anywhere from a few months to a few years, the nickel sulphide
converts to the larger size and that expansion of the nickel sulphide
creates stresses in the glass.
If the nickel sulphide inclusion is in the perimeter compression zone
of the glass, the glass may survive the expansion forces.
However, if the nickel sulphide inclusion is in the tension zone in the
interior of the glass, the expansion forces can cause spontaneous
breakage.
The problem of nickel sulphide inclusions is not new. However, as
the size of glass balcony panels has increased, so has the probability
of having a nickel sulphide inclusion in the tension zone of a
particular panel.
There is a telltale sign that a nickel sulphide inclusion has caused a
panel to break, and that is a “Double D” or butterfly pattern in the
broken glass at the point of the inclusion. When a breakage has
occurred, examine the broken glass for this sign before it is cleaned
up to determine whether a nickel sulphide inclusion was the cause of
the breakage, as opposed to a projectile. The likelihood of a piece of
glass breaking due to a nickel sulphide inclusion will tend to decrease
over time.
There are varied opinions as to what is an “acceptable” breakage rate.
While building owners would like to see zero breakage, it is this
author’s opinion that two breaks in 1,000 panels should not be
considered unusual. If a building experiences more breaks than this,
seek professional expertise to determine an appropriate course of
action to minimize further breakage.
Contact breakage
Glass breakage can also be caused by glass-to-metal contact or by
glass-to-glass contact. The simple act of the glass edge rubbing
against a mounting plate, a guard post or the edge of an adjacent piece
of glass can cause the glass to break. Breakage can also be caused if
there is a temperature difference between glass and metal if they are
in contact.
To prevent such contact, appropriate clearances must be maintained,
typically by mounting the glass on setting blocks (pieces of neoprene,
EPDM, silicone, or other elastomeric material) and using gaskets or
sealant to separate glass from metal supports. One of the problems that
has occurred with the larger sizes of glass panels now being used as
balcony guards is that, due to their weight, they are difficult to
handle and assure that the appropriate clearances are maintained when
they are installed.
Also, over time, if a glass panel is not secured on all four sides, it
may shift its position due to buffeting from wind or movement of the
building structure. So even if correctly installed in the first
instance, over time, contact breakage may increase. Unlike a nickel
sulphide inclusion problem, shifting of panels can be readily observed
and corrected before breakage occurs.
New requirements for new construction
In 2011, following a series of cases of glass balcony guards breaking,
the Ministry of Municipal Affairs and Housing struck an expert panel to
study the issue. In 2012, the Ontario Building Code was amended to
include Supplementary Standard SB-13, which became effective July 1,
2012.
The supplementary standard prescribes requirements for the design and
construction of glass in guards that are intended to reduce the
probability of breakage or injury; it is recognized that it is not
possible to eliminate breakage. One such requirement is to use
heat-strengthened laminated glass for guards located beyond the edge of
a floor (e.g. on the face of the balcony slab).
SB-13 is applicable only to new construction or when a major renovation
is being undertaken, such as the replacement of the balcony guards. The
supplementary standard does not require existing balcony guards to meet
its requirements.
Can glass breakage be prevented?
Unfortunately, it is impossible to entirely eliminate nickel sulphide
inclusions in glass, so it’s difficult to prevent all glass breakage.
However, there are steps that can be taken to ensure that the risk of
injury is minimized if glass does break.
Heat soaking
Some experts recommend that tempered glass be heat soaked to determine
if it has, or likely has, nickel sulphide inclusions. In this process,
the tempered glass is reheated in a controlled factory environment to
force breakage of glass with nickel sulphide inclusions. The problem
with this approach is that it adds significantly to the cost of the
glass, and some uncontaminated glass may break, further adding to the
cost. However, using only heat-soaked glass will certainly minimize, if
not eliminate, the use of glass with nickel sulphide inclusions.
Buffer zone
A buffer zone, about 20 feet wide, can be created around the perimeter
of the building using planters or other means to limit pedestrian
access. Should a glass panel break, injury will be minimized as there
should be no one in the area where the glass falls. Of course, this
approach may not be feasible in dense, urban areas.
Support of the glass panel
In recent years, framing around glass balcony panels has been reduced
or even eliminated in some cases. This has resulted in the need for
thicker pieces of glass to compensate for the reduced structural
contribution from framing. And thicker glass increases the chances of
nickel sulphide inclusions in the tension zone of the glass.
Designing balcony guards with metal framing allows thinner glass to be
used, reducing the probability of a nickel sulphide inclusion.
In some designs, the balcony panels are mounted on the face of the
balcony slab rather than on the top of the slab. When the glass breaks,
all of the glass will fall to the ground. Some experts believe that
keeping the glass back from the edge of the balcony slab will minimize
the amount of glass falling to the ground and potentially injuring
someone.
Laminated glass
On some new buildings, laminated glass is being used for balcony
guards. An interlayer film bonds layers of glass together. As a result
of the glass being held together, it is less likely that glass pieces
will fall to the ground should the glass break.
However, this approach will only work if the laminated glass is held
securely in a frame. If the laminated glass is not held on all four
edges, it could fall, and a large piece of falling laminated glass is
likely to cause more injuries than small pebbles of tempered glass. For
this reason, the use of structural silicone sealant on the exposed
edges is recommended to adhere laminated glass to adjacent metal posts.
For retrofits, there are films that can be applied to the surface of
the glass to hold it together should it break. To be properly applied,
the balcony glass should be removed from its supports so that the
entire surface of the glass can be covered with the film, not just the
area of glass within the inside perimeter of any framing. As with
laminated glass, if a film is applied, the glass must be secured in
place on all four sides.
It is difficult to install such films outside of a controlled
environment, and as the films are on the surface of the glass, they are
prone to degradation due to ultraviolet radiation from the sun. It is
preferable to use laminated glass rather than apply films, though the
use of laminated glass would require complete replacement of the glass,
which is an expensive proposition.
As noted earlier, while glass breakage due to nickel sulphide decreases
over time, contact breakage will increase. Annual inspections of
balcony guards are recommended to identify potential glass-to-metal or
glass-to-glass contact and to take corrective action. These
inspections can be conducted by the property manager.
Dale D. Kerr, M.Eng., P.Eng., BSSO,
ACCI, is a building science specialist with GRG Building Consultants
with more than 30 years’ experience in assessing and repairing
buildings.
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Infinity pool’s glass panels crash from Whampoa condominium The Star Online
09 July 2016
Glass panels surrounding the swimming pool fell from Cradels@Whampoa, a condominium, on July 8, 2016. Photo: SHULI SUDDERUDIN
SINGAPORE: Glass panels from a condominium swimming pool off Balestier
Road crashed from the fifth floor to the ground on Friday afternoon.
Shuli Sudderudin, 31, who lives in the condominium beside Cradels@
Whampoa, said she first heard a loud crash like a “big metal thing
falling” while she was at home.
She left her home half an hour later, and was walking past the condominium when she heard the sound of “a small waterfall”.
She looked up and realised that water was pouring from the swimming
pool at Cradels@Whampoa down the building. Then, she saw another glass
panel tumble from above.
A photo taken by Shuli showed a glass panel dangling in mid air. A number of other panels appeared to be missing.
She was outside the fence of the condominium but still alarmed, she said.
“Water sprayed everywhere over the road in front. It was quite
dramatic. I was standing there and people came rushing out and yelling
and telling me not to stand there as another glass panel shattered,”
she said.
The Singapore Civil Defence Force said it was alerted to the incident at 2.32 pm. No injuries were reported.
A Building Construction Authority (BCA) spokesman told ST: “Upon
arriving at the site, BCA engineers found that a row of glass panels,
that act as a safety barrier for a stretch of maintenance ledge on the
outer edge of the swimming pool, had fallen off from the fifth floor.
The glass does not contain the water in the swimming pool.
“In the interest of public safety, BCA has directed the owner of the
building to close the entire fifth storey and the affected area below
the fallen glass panels. The owner will be required to appoint a
Professional Engineer to advise on the necessary precautionary measures
to remove any danger, carry out a detailed investigation assess the
structural condition and recommend permanent rectification works.
“Under BCA’s building regulations, glass that is used as a safety
barrier must be laminated glass and designed to withstand horizontal
loading determined in accordance with prescribed standards. For
infinity edge pools, the industry is required to incorporate reasonable
safety measures in the infinity pool design to mitigate the risk of
falling from height.”
– The Straits Times/Asia News Network
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Building must undergo safety review after pane of glass falls from condo balcony CTV News
14 September 2016
City inspectors have ordered a downtown condo building to complete a
safety review after a pane of glass fell to the ground Wednesday
morning.
It happened around Simcoe Street near Adelaide Street just before 8 a.m.
The pane fell from the 26th floor, according to Bruce Hawkins from the
City Planning department. Initial reports said the pane fell from the
25th floor.
A pane of glass fell from a downtown condo building on Sept. 14, 2016. (Stephanie Smyth/CP24)
The building must now retain the services of a professional engineer to
determine the cause of the glass breaking, and any links to a previous
failure, Hawkins told CTV Toronto. The building must also complete a
detailed review of the glazing and balcony system to determine what, if
any, remedial action is required.
There were no injuries.
It was not immediately clear what caused the window to fall, however,
Hawkins said it is not believed to have been from any sort of impact.
Police said a large shard of glass was hanging from the balcony where the pane fell from.
As a precaution, police closed a portion of Simcoe Street, Nelson Street and Duncan Street.
While the area remained closed, guests at the nearby Shangri-La Hotel have been instructed not to use its Simcoe Street doors.
This is the second time glass has shattered at this building. In August
2015, another pane of glass from a 26th floor balcony shattered.
Hawkins could not confirm whether the glass that fell Wednesday morning was from the condo unit with the same problem in 2015.
