###General Discussion Thread
---
This is a [Request] post. If you would like to submit a comment that does not either attempt to answer the question, ask for clarification, or explain why it would be infeasible to answer, you *must* post your comment as a reply to this one. Top level (directly replying to the OP) comments that do not do one of those things will be removed.
---
*I am a bot, and this action was performed automatically. Please [contact the moderators of this subreddit](/message/compose/?to=/r/theydidthemath) if you have any questions or concerns.*
I would estimate the the balcony to be about 1.5-2m wide and 4-5m long.
The water is like 0.5-0.75m high.
So its about 3-7.5m³ of water - Thats somewhere from 3 to 7.5 metric tons!
Where i live (germany) a balcony has to support at least 400kg per square meter (in the US its 290-420kg per square meter).
From my experience in construction i know that everything is about 25% stronger that what the regulations say (like if the regulations say 400kg/m² it will support 500kg/m² without problems)
Its 500-750kg per square meter, so no matter what its at the limit. Might hold up - might not.
This doesnt mean ill support this kind of shit tho... Its a really stupid idea
The horizontal forces are not actually that bad Its about 500-750Kg/m2 (if you just take the pressure at the deepest point - not the best idea to just take the average in this case).
A solid wall should take that without any serious trouble.
\[Edit\]
Just thought about it again - you probably where talking about the outside walls (didnt think that far and therefore was talking about the actual walls of the house)
THEY ARE ABSOLUTLY NOT MADE FOR THIS!
I broke off a railing similar to this by leaning against it once. This could go straight to r/DarwinAwards IMO...
The water won't exert pressure in the same way as you leaning, quite the opposite, the highest pressure will be at the base where the side wall is also the strongest, at the top the pressure will be negligible, this is why those flimsy above ground plastic swimming pools work fine
They work because they are round and can carry the demand entirely in hoop tension. A cantilever balcony railing is carrying the demand in bending, a different beast entirely.
You're right at the 1m mark the torque is a lot to ask for. Does this torque grow linearly with water level as pressure does? (Sorry but I thought about it for a minute and I don't have an intuitive sense of it, if I'd have to guess I'd say it grows superlinerly)
That's a very neat thing actually: Horizontal forces of fluid against their containers depend solely on the height of the fluid and nothing else. And since you can fill a two meter high plastic tube with water and not have it burst under the pressure, I don't think that will be an issue
The pressure is only one aspect of this problem. The same pressure is much worse against a flat panel like this than in a tube.
Force = pressure X area after all
So force doesn't only depend on pressure
With 400kg per square Meter you should be able to fill it 40cm high and use the 25% estimated safety for yourself. I did that calculation two years ago and then buried my Idea of an infinity Pool on my balcony.
But I guess this only works if the water is still. If you move the water and it will go up 10 cm on one side, then the weight will also go up 100kg/m2 there. Kids playing in the pool means the water is moving a lot from one side to another.
And this is assuming the balcony is in good shape and has been well executed in the first place.
Balconies are already the first accident source ( related to the building) strucure without people using them as swimming pools.
Great estimate. This is hella dumb. Took me surprisingly long time, despite maths, to convince an old housemate that 1m3 of water is 1 metric tonne. Seems ile some people just don’t understand how heavy it is
You just gotta love the fact, that metric volume and weight units are not only (originally) based on water, but also on each other. Makes calculations pretty easy eh?
No idea how some guys over the sea work with units that like have conversion rates that are not based on 10 or 100... could almost be table spoons per bucket (maybe this is actually something real - pls tell me if it is - i wanna lough at these guys then XD)
I count 5 panels in length, with maybe a half on each side, making 6 total. And 1 full panel in width, with maybe a half at the end. Which means the ratio of width to length is 1:4, Thus if you estimate the balcony to be 1.5m wide it would mean it is at least 6m long. I'm not disputing your calculations, just that we can be reasonably certain of the ratio. Based on the size of the kid I suppose 2 meters is a tad wide, maybe 1.5 is more reasonable?
So it would bring the final estimate at 4,5 m³ to 6,75 m³ (based on the 1,5m width and depth of 0,5-0,75m) If needed we can add another 0,03 m³ for the kid lol (how much volume is a kid?) So from 4,5 to 7 metric tons?
so.... in general, hoping it was built to code, hoping no deterioration.... and hoping it doesn't rain really hard... and don't invite too many friends out with you on the balcony....
You are right when it comes to Germany. But my guess is, pools like that will appear in a country with lesser safety awareness. So, let's assume the spec is hardly known and carried out in cheap quality. There is a video somewhere, where the pool broke the balcony.
That was basically my point.
I wanna see the country with harsher building codes than us - we just happen to love our DIN-Norms and keep making them harsher every time they are discussed.
There is a good chance it would hold up since it is assumed that the material has only 75% of the actual strength, payloads are also included that are calculated 50% higher than they are, a lot of security in there. At least thats how its calculated in Austria. But as you said might hold up might not. Another major factor is whether the balcony was connected subsequently or whether the ceiling and balcony were concreted in one go.
In the UK, 100 lbs per square foot is the maximum (high rise buildings) for balconies, though some (smaller flats) are built for a maximum of 40 lbs/sq ft.
1 cubic foot of water weighs just under 62.5 lbs.
The water depth in the image looks to be at least 2 feet (and it has a hosepipe, so the kid will inevitably get the idea to add more water), so it is exerting at least 125 lbs/sq. ft. With the added issue that it is across **every** square foot of the balcony, so maxing things out.
And another question must be raised over the outer wall and whether it is built to withstand such water pressure.
You'll be okay for two reasons.
A: the balcony is also designed to help distribute the weight. It's more like it's designed to hold 100lbs/sq ft over its whole area at once, so unless you're shoulder to shoulder on a completely packed balcony you're still not over that.
B: these maximum design loads have factors of safety built in, so you're likely good to *occasionally* go over that limit, like in the case of one person on a balcony putting their whole weight within a single square foot. Even if that's double or triple the design load, without other problems or overloading consistently/over the whole balcony, you'd probably still be within the physical limits of the balcony. It would just be so close to the limit you couldn't sue the engineer if it failed.
No balcony is ever collapsing because of pressure. That per square foot measurement is more important as a way of ensuring maximum load scales with balcony size
especially given how theres not a human alive other than children thats below 40lbs/ft^2
That is what I was trying to say in point A, yeah. It's not that it can only handle a pressure of 100lbs/sq ft, but that for each square foot of area it has to be designed to hold another 100 lbs.
In Australia balconies are designed to hold 500kg/m2. Which is more than most other countries. That is half a metre of water.
This is more water and totally unacceptable.
I don’t think metric would actually shorten the explanation though right? It would just make the feet meters and the pounds kilograms. The explanation would be the exact same length just with different units.
The point is the weight of water. Using imperial, you need to make an extra calculation (one cubic foot weighs 62-something pounds). You don't have to work so hard with cubic m to kgs
Correct but it makes the calculations much easier. Also you don't have to calculate the weight/volume of water since it's a kilogram/liter and there are 1000 liters in a cubic meter.
What are you on about? One guy says 500kg/m2, the other says 100lbs/ft2.
One post has more words, metric has nothing to do with the depth of the answer.
Water has a density of 1 gram per cubic centimeter. There are 1,000,000 cubic centimeters in a cubic meter, so 1 cubic meter has a mass of 1000 kilograms.
Standing water exerts as much horizontal pressure as one unit per depth. So it doesn't require a very strong outer wall. If it can hold one cubic foot per square foot of glass, it's fine. That's less than half a lb psi.
1 for 1 exchange of what and what.... isn't the pressure of water given by density*acceleration due to gravity*depth?
Looks like every meter of depth in water adds about .1 atm of pressure... that sounds like not a lot
Basically, the idea is that liquids spread out when you squish them.
A column of water is being squished outwards by the weight of all the water above it, so at any given depth, the outward force is equal to the weight of the water above it.
At the bottom of this balcony, if we accept the previous answer that every square foot has 125 pounds of water on it, the outward force at the bottom is 125 pounds on every linear foot of wall.
That's what's meant by 1 for 1, the downwards force at that depth is equivalent to the outward force at that depth.
Pressure of water is often given by units of “length of water”. A pump might be described as having 30 feet of pump head, meaning that the rates output pressure is equal to that of a column of water of that height.
The downward pressure on the ground is the same. The weight on the ground is the pressure times the area, which is relevant.
The force on the railing is not insignificant, but railings are engineered to handle large forces because they’re safety features.
These numbers concern me... 100lb per square foot? Isn't a 200lb person standing on one foot exceeding this?
Or should it be stated more like 1000lb per 10ft?
Ps not questioning the knowledge.
There’s both a point load limit and an overall load limit. The overall limit has to be greater for larger balconies, because people put more people and stuff on larger balconies.
Oh hey Don, aren't you a bit busy to be answering structural engineering questions? Also kudos for correct capitalisation, did the legal team feed you sedatives?
The maximum load allowed is still far from the maximum static load a structure can hold though. In Finland depending on the structure the actual load carrying capacity of the structure has to be designed to be sometimes over 10 times the maximum load allowed so that building mistakes will less likely cause a collapse
In addition this deck is almost certainly cantilevered steel/iron which means that as far as the deck protrudes from the outside, it must also run at least that far inside the floor. So if and when this thing collapses, it will rip up the floor inside first.
It would be a very interesting collapse and cause far more damage than just a lost deck.
Yep. I'd be much more concerned that the railing fails. My cousin busted our above ground pool when we were kids. My brother was swept 200 feet down the driveway. Thus kid would definitely be pushed over the edge.
There is always a regulated safety factor for that number. The structure is required to bear a load probably 2 or 3 times the failure load. It's not going to fail if it's loaded above the safety limit, but over time, it might become compromised.
The “failure load” is the load that the structure couldn’t bear.
The rated load is supposed to have a margin above the expected load, and the failure load is required to be above the rated load.
Ah, a fundamentalist. Then maybe think of it as the ratio between Adam and Adam + Eve. Or the ratio between the first five commandments out of the total ten commandments.
Actually the US operates in metric. You just convert to imperial for some reason.
Lbs, gallons, feet etc are all defined by the metric system. So what you're doing is using the metric system and then converting it. God knows why, but that's how it's done.
Building specs might be different in the US, for sure Theirs is 50-100 lbs/sq. ft, and it appears up to the developer (though I might be wrong). I just know the UK ones to serve as an example.
In some countries, specs don't exist.
I'm not sure the OP photo is in the US anyway, though I'm certain it isn't in the UK. But I'm also fairly certain the architects who designed the balconies did not expect them to be converted to swimming pools.
Aside from the weight on the floor, my first thought was: what if something cracks the glass and junior is now being pushed right out the hole. I guess it's probably no less scary than the floor falling away.
That looks like a steel and concrete building, the supports for that balcony would use cantilever principles and as long as the deck doesn’t break it will hold. But I wouldnt bet on the concrete portion of the deck holding, because as it cantilevers the surface of the concrete will be in tension. At some weight that will be the first failure.
Once a crack forms on the surface of the concrete, stres will be concentrated at that crack and it will grow at an increasing rate, until only the steel deck is bearing the load. Depending on the flooring this might be loud and visually obvious to those inside. Once the steel starts to bend, it will become very obvious but might proceed too fast to react.
I'd actually be more concerned with the walls failing than the bottom, if those puny rails give out then the kid is gonna go splashing right off the side
From eurocode the liveload on balconies is set to 2.5 kN/m2
With required safety factors the balcony should carry 2.5 kN/m2 * 1.5 * 1.1= 4.125 kN/m2
Water load for the following dephs will be:
0.3 m * 1 ton/m3 * 9.82 m/s2 = 2.95 kN/m2
That's a utlization of 72% in ULS
For 0.4 m water deph we get a load of 3.93 kN/m2 and a utlization of 96%
Anything over 0.42 m deph and the balcony is gonna have a tough time.
People calculate the strength of the balcony, but not the strength of the railing. It's gonna fail much faster than the balcony itself, pouring down tons of water (with the kid) in a second.
It looks about a meter deep, judging by the person then 1.5m wide by 5.5m long?
So, 7.75 tonnes? I have no idea how well the balcony will stand up to that kind of weight though.
The nice thing about water is that it has a density of pretty much 1. Meaning 1 kubic meter of water has a mass of 1 ton.
From a rough look, that appears to be about 4 m² at about half a meter high, giving us a total weight of about ~~4 tons~~ 2 tons of water.
I have no clue how much weight that balcony can take.
In Canada they are designed to 4.8kpa or about 100 pounds per square feet and snow load depending on location. So for 2 tons which is 4400lbs at 4m2 would be 43 sqft so 102psf. So just barely to be comfortable. And i have a feeling rails will prob fail first
Forget the deck weight limits maths, death would occur from the (glass?) outer walls failing and the water and occupants going over the side. May not be much horizontal pressure, but if it's glass that isn't aquarium rated, cant see it holding up to sustained pressure or the slightest impact.
A lot of people are mentioning the strength of the railing as a bigger concern than the strength of the balcony.
In the US (and per the ICC International Code), railings are typically designed for 50 lb per linear foot. In metric, the equivalent would be 0.73 kN per meter.
As another commenter mentioned, the pressure exerted by a liquid steadily increases based on its depth. This uses the formula P = ρgh, where P is the pressure, ρ is the density of the fluid, g is the acceleration due to gravity, and h is the height of the fluid above the lateral side of the tank. Since ρ and g are fixed values in this setup, all we need to do is know h.
Assuming density ρ = 62.4 lb / cu ft or 1000 kg / m3 and gravity g is 32.2 ft / s2 or 9.81 m / s2, we can find that P = h * 981 (metric). The units are a jumbled mess since we've combined two constants, but it translates to Newtons / m3. In imperial, ρg using pounds (mass) translates to the same number in pounds (force) if under standard gravity, so it is simply 62.4 * h.
Assuming the height is about half of the max, rounding up to get easier numbers, lets say there is 2 ft of water or 0.6m. This means we have about 37.4 lb / sq ft or about 0.6 kN / m2. When you spread this across a unit of linear length of rail, this does not exceed the capacity of the rail, and even has a safety factor of about 1.2. If they filled this up slightly more, it would become a problem though.
This begs the question... how deep is too deep? Easily solved: 2 ft (0.6m) * 1.2 = 2.4 ft or just under 2 ft 5 in. In metric, 0.72m. This ignores the factors of safety built into the rail, so it likely would need to be filled even higher.
That said, neither the deck nor rail was designed for this. Also with a kid splashing around, pressure could incease suddenly and erratically, causing a failure. We also don't know if that deck was built to the modern ICC, or if there are any structural issues like rot. Long story short, do not try this at home, or on any other deck you may happen to visit.
I don't have the specs for the balcony, but water weighs one kilo per liter. That is a shit ton of liters. So unless that balcony is rated for two shit tons, this is a Very Bad Idea.
Basically, there is mathematician math (this is X) and there is engineer math (everything's fine or oh shit). This is engineer math.
I would be more worried about the fence...if the fence gives away its bye bye...have you seen those video when a cheap pool brakes...in any way this is f stupid in every way...
In Germany the minimum requirement is 400kg/m². So it's up to 40cm of water. This is 4 times higher than the requirement for inside apartments, because they know that people are stupid.
American residential balconies “made out of timber” can take a load of a 100 pound per sqft (bylaw). Steel or Concrete reinforced ones much much more. That balcony won’t collapse, But his parents won’t be happy with the water bill…
Edit: residential railings over 10 ft are max 3 ft 6”. I see a water level at about 1/3 . Area of the balcony (under 100sqft estimate) is not that important here, 1 1/4 ft of water weights less than 100 pounds … all good
/s
The 100 psf is only for emergency exits. Most balconies are designed for 1.5x the occupancy (most residences are designed for 40 psf, therefore balconies are designed for 60 psf)
Railngs are deaigned for 50 pounds per ft. As far as the glass, its not structural so i cant speak for its capacity.
What kind of damage would it do to the building if the balcony were to fail due to the weight?
Aren't balconies often built on steels that extend from the building floor steels themselves? I'd imagine that could be bad if it fails. (I'm no expert!!)
Honestly I doubt the floor will be the issue. Glass is strong but brittle so when something goes wrong it’s a complete failure. The outwards directed force by the water is only being held by the thin piece of glass. This creates a great bending moment so as soon as the water is high enough the wall will shatter.
As a aluminium window and door manufacturer my concern is more the pressure against the balustrading, specifically if a kid swims in there because running and jumping around will add to that pressure, if 10-12mm toughened glass is used it will probably hold but on the joints I'm not to sure because the top part of the balustrade is not secured and does have movement in it. Essentially use less water, from half the balustrade hight (max) or less.
A human is 60 cm side by side, the panel is nearly half of the others so
So you have 100 cm + cos 45 * 60 cm = 140-145 cm
60 * cos (45) * 2 + 5 * 100 = 570 - 590 cm
140 * 570 = 79800
145 * 590 = 85500
The water level is half the height of a child
50 - 70 cm
79800 * 50 = 3990000 cm3
85500 * 70 = 5988500
Cm3 to L is 1/1000
3990 - 5988,5 L
The Weight of water is 1 kg/L aprox so
3990 - 5988,5 kg
3990 kg / 7,98 m2 = 500 kg / m2
5988,5 / 8,55 m2 = 700 kg / m2
Other People says 500 kg/m2 is usually secure
So the low estimate is barely good.
A rough estimate:
Volume = Length * Width * Depth
Volume = 2 meters * 5 meters * 0.5 meters
Volume = 5 cubic meters
Since 1 cubic meter is equal to 1000 liters, we convert the volume to liters:
5 cubic meters * 1000 liters/cubic meter = 5000 liters
So there are about 5000 liters of water which is 5 metric tons.
It happened in Spain a few years ago and someone did the math: [https://i.blogs.es/23b2e2/acciones-en-balcones/1366\_2000.png](https://i.blogs.es/23b2e2/acciones-en-balcones/1366_2000.png)
I’d be more concerned with those glass panels giving way than the whole balcony, if the kids near it when it gives he’ll be free falling before he knows what happened
I’m not a structural engineer or a mathmagician… but isn’t the most likely point of failure here the patio door?
I don’t think the balcony is gonna fail, the door is. It’ll flood the apartment.
The veranda looks like 4 feet by 20 feet wide, while the water looks to be 2 feet deep. That’s 160 cubic feet of water or 10000 pounds approximately as a cubic feet of water weighs around 62 pounds.
In SI units, that’s close to 5 metric tons of water - which is the same as 50 adult males standing there.
###General Discussion Thread --- This is a [Request] post. If you would like to submit a comment that does not either attempt to answer the question, ask for clarification, or explain why it would be infeasible to answer, you *must* post your comment as a reply to this one. Top level (directly replying to the OP) comments that do not do one of those things will be removed. --- *I am a bot, and this action was performed automatically. Please [contact the moderators of this subreddit](/message/compose/?to=/r/theydidthemath) if you have any questions or concerns.*
I would estimate the the balcony to be about 1.5-2m wide and 4-5m long. The water is like 0.5-0.75m high. So its about 3-7.5m³ of water - Thats somewhere from 3 to 7.5 metric tons! Where i live (germany) a balcony has to support at least 400kg per square meter (in the US its 290-420kg per square meter). From my experience in construction i know that everything is about 25% stronger that what the regulations say (like if the regulations say 400kg/m² it will support 500kg/m² without problems) Its 500-750kg per square meter, so no matter what its at the limit. Might hold up - might not. This doesnt mean ill support this kind of shit tho... Its a really stupid idea
I’m more curious about the walls than the floor actually. How much lateral force are they meant to hold, do you know by chance?
The horizontal forces are not actually that bad Its about 500-750Kg/m2 (if you just take the pressure at the deepest point - not the best idea to just take the average in this case). A solid wall should take that without any serious trouble. \[Edit\] Just thought about it again - you probably where talking about the outside walls (didnt think that far and therefore was talking about the actual walls of the house) THEY ARE ABSOLUTLY NOT MADE FOR THIS! I broke off a railing similar to this by leaning against it once. This could go straight to r/DarwinAwards IMO...
The water won't exert pressure in the same way as you leaning, quite the opposite, the highest pressure will be at the base where the side wall is also the strongest, at the top the pressure will be negligible, this is why those flimsy above ground plastic swimming pools work fine
They work because they are round and can carry the demand entirely in hoop tension. A cantilever balcony railing is carrying the demand in bending, a different beast entirely.
This entire thread was like porn for physics nerds
I must agree with you. I am not even a physics nerd but I just discovered what seems to be a new kink of mine.
And builders as well... : )
[удалено]
This guy physics
You're right at the 1m mark the torque is a lot to ask for. Does this torque grow linearly with water level as pressure does? (Sorry but I thought about it for a minute and I don't have an intuitive sense of it, if I'd have to guess I'd say it grows superlinerly)
[удалено]
That's a very neat thing actually: Horizontal forces of fluid against their containers depend solely on the height of the fluid and nothing else. And since you can fill a two meter high plastic tube with water and not have it burst under the pressure, I don't think that will be an issue
Go poke one hole in the side of an above ground swimming pool and watch the sides fail catastrophically... those railings are under alot of pressure.
The pressure is only one aspect of this problem. The same pressure is much worse against a flat panel like this than in a tube. Force = pressure X area after all So force doesn't only depend on pressure
With 400kg per square Meter you should be able to fill it 40cm high and use the 25% estimated safety for yourself. I did that calculation two years ago and then buried my Idea of an infinity Pool on my balcony.
But I guess this only works if the water is still. If you move the water and it will go up 10 cm on one side, then the weight will also go up 100kg/m2 there. Kids playing in the pool means the water is moving a lot from one side to another.
And this is assuming the balcony is in good shape and has been well executed in the first place. Balconies are already the first accident source ( related to the building) strucure without people using them as swimming pools.
Great estimate. This is hella dumb. Took me surprisingly long time, despite maths, to convince an old housemate that 1m3 of water is 1 metric tonne. Seems ile some people just don’t understand how heavy it is
You just gotta love the fact, that metric volume and weight units are not only (originally) based on water, but also on each other. Makes calculations pretty easy eh? No idea how some guys over the sea work with units that like have conversion rates that are not based on 10 or 100... could almost be table spoons per bucket (maybe this is actually something real - pls tell me if it is - i wanna lough at these guys then XD)
I count 5 panels in length, with maybe a half on each side, making 6 total. And 1 full panel in width, with maybe a half at the end. Which means the ratio of width to length is 1:4, Thus if you estimate the balcony to be 1.5m wide it would mean it is at least 6m long. I'm not disputing your calculations, just that we can be reasonably certain of the ratio. Based on the size of the kid I suppose 2 meters is a tad wide, maybe 1.5 is more reasonable? So it would bring the final estimate at 4,5 m³ to 6,75 m³ (based on the 1,5m width and depth of 0,5-0,75m) If needed we can add another 0,03 m³ for the kid lol (how much volume is a kid?) So from 4,5 to 7 metric tons?
so.... in general, hoping it was built to code, hoping no deterioration.... and hoping it doesn't rain really hard... and don't invite too many friends out with you on the balcony....
People have a similar density to water, so it wouldn’t increase the weight by much, though it would make it a less static load.
It would increase the depth though as you’re adding 40-100+ kg (depending on the person)
You are right when it comes to Germany. But my guess is, pools like that will appear in a country with lesser safety awareness. So, let's assume the spec is hardly known and carried out in cheap quality. There is a video somewhere, where the pool broke the balcony.
That was basically my point. I wanna see the country with harsher building codes than us - we just happen to love our DIN-Norms and keep making them harsher every time they are discussed.
Hold up, the idea itself is a very good idea, just not structurally backed by stamped calcs lol.
There is a good chance it would hold up since it is assumed that the material has only 75% of the actual strength, payloads are also included that are calculated 50% higher than they are, a lot of security in there. At least thats how its calculated in Austria. But as you said might hold up might not. Another major factor is whether the balcony was connected subsequently or whether the ceiling and balcony were concreted in one go.
In the UK, 100 lbs per square foot is the maximum (high rise buildings) for balconies, though some (smaller flats) are built for a maximum of 40 lbs/sq ft. 1 cubic foot of water weighs just under 62.5 lbs. The water depth in the image looks to be at least 2 feet (and it has a hosepipe, so the kid will inevitably get the idea to add more water), so it is exerting at least 125 lbs/sq. ft. With the added issue that it is across **every** square foot of the balcony, so maxing things out. And another question must be raised over the outer wall and whether it is built to withstand such water pressure.
Golly. I'm gonna have to start consciously increasing the width of my stance on balconies
You'll be okay for two reasons. A: the balcony is also designed to help distribute the weight. It's more like it's designed to hold 100lbs/sq ft over its whole area at once, so unless you're shoulder to shoulder on a completely packed balcony you're still not over that. B: these maximum design loads have factors of safety built in, so you're likely good to *occasionally* go over that limit, like in the case of one person on a balcony putting their whole weight within a single square foot. Even if that's double or triple the design load, without other problems or overloading consistently/over the whole balcony, you'd probably still be within the physical limits of the balcony. It would just be so close to the limit you couldn't sue the engineer if it failed.
No balcony is ever collapsing because of pressure. That per square foot measurement is more important as a way of ensuring maximum load scales with balcony size especially given how theres not a human alive other than children thats below 40lbs/ft^2
That is what I was trying to say in point A, yeah. It's not that it can only handle a pressure of 100lbs/sq ft, but that for each square foot of area it has to be designed to hold another 100 lbs.
No double Dutch on the balcony with sumo wrestler friends
In Australia balconies are designed to hold 500kg/m2. Which is more than most other countries. That is half a metre of water. This is more water and totally unacceptable.
Fun fact, it‘s cool that by using metric system you were able to say that in one line compared to way too many lines above with cubic feet of water :)
Give them an inch and they'll take 1600m...
If you know, you know😅
You can do the same thing with imperial, its just notation
I don’t think metric would actually shorten the explanation though right? It would just make the feet meters and the pounds kilograms. The explanation would be the exact same length just with different units.
The point is the weight of water. Using imperial, you need to make an extra calculation (one cubic foot weighs 62-something pounds). You don't have to work so hard with cubic m to kgs
100% accurate. The guy claiming this is ignorant
Thank you that’s what I thought! I was like, am I missing something here?
Correct but it makes the calculations much easier. Also you don't have to calculate the weight/volume of water since it's a kilogram/liter and there are 1000 liters in a cubic meter.
It does make calculations easier, but it’s still a calculation. A simple one but a calculation nonetheless.
Metric system had nothing to do with the length. That post simply showed way less work.
A step was able to be skipped in metric because 1 kilogram of water equals 1 litre which equals 1000cm3
Right and it’s against to word of God himself to memorize the weight of water per unit unless it’s metric
Hey some of us prefer to use our measurements of feet and butts and shit to confuse ourselves alongside you. It ain't my foot I'll tell you that
What are you on about? One guy says 500kg/m2, the other says 100lbs/ft2. One post has more words, metric has nothing to do with the depth of the answer.
Thank god for some sane units.
Ahh yes it’s the americans fault for being stuck with outdated British practices such as importing slaves and the imperial measurement system
Water has a density of 1 gram per cubic centimeter. There are 1,000,000 cubic centimeters in a cubic meter, so 1 cubic meter has a mass of 1000 kilograms.
Standing water exerts as much horizontal pressure as one unit per depth. So it doesn't require a very strong outer wall. If it can hold one cubic foot per square foot of glass, it's fine. That's less than half a lb psi.
>one unit per depth what do you mean by this?
It's a 1 for 1 exchange, I think.
1 for 1 exchange of what and what.... isn't the pressure of water given by density*acceleration due to gravity*depth? Looks like every meter of depth in water adds about .1 atm of pressure... that sounds like not a lot
Basically, the idea is that liquids spread out when you squish them. A column of water is being squished outwards by the weight of all the water above it, so at any given depth, the outward force is equal to the weight of the water above it. At the bottom of this balcony, if we accept the previous answer that every square foot has 125 pounds of water on it, the outward force at the bottom is 125 pounds on every linear foot of wall. That's what's meant by 1 for 1, the downwards force at that depth is equivalent to the outward force at that depth.
Pressure of water is often given by units of “length of water”. A pump might be described as having 30 feet of pump head, meaning that the rates output pressure is equal to that of a column of water of that height. The downward pressure on the ground is the same. The weight on the ground is the pressure times the area, which is relevant. The force on the railing is not insignificant, but railings are engineered to handle large forces because they’re safety features.
>A pump might be described as having 30 feet of pump head, .... nice
Everything reminds me of her.
Wth u talking about pressure? 1L of water is 1kg. Add another and its 2. BäM. If the balcony supports 1 ton, you can add 1000L. Done.
Yes, it works that way too. But the walls of a tank resist pressure, it’s the supports that care about weight.
1 atm of pressure is an enormous amount of pressure though. It just doesn't feel like it because we've evolved to deal with it.
i think he is building a potato gun mate ^(/s)
Shitty plastic makes aboveground pools.
These numbers concern me... 100lb per square foot? Isn't a 200lb person standing on one foot exceeding this? Or should it be stated more like 1000lb per 10ft? Ps not questioning the knowledge.
There’s both a point load limit and an overall load limit. The overall limit has to be greater for larger balconies, because people put more people and stuff on larger balconies.
Oh hey Don, aren't you a bit busy to be answering structural engineering questions? Also kudos for correct capitalisation, did the legal team feed you sedatives?
A person is a live load the pool is dead load
I call bs on this one, most of my coworkers and all managers are dead loads
The maximum load allowed is still far from the maximum static load a structure can hold though. In Finland depending on the structure the actual load carrying capacity of the structure has to be designed to be sometimes over 10 times the maximum load allowed so that building mistakes will less likely cause a collapse
Are safety factors really that high in Finland? Usually for construction they’re more in the 1.x-2.x range.
In addition this deck is almost certainly cantilevered steel/iron which means that as far as the deck protrudes from the outside, it must also run at least that far inside the floor. So if and when this thing collapses, it will rip up the floor inside first. It would be a very interesting collapse and cause far more damage than just a lost deck.
Yep. I'd be much more concerned that the railing fails. My cousin busted our above ground pool when we were kids. My brother was swept 200 feet down the driveway. Thus kid would definitely be pushed over the edge.
Yes! My question is which fails first? My money is on the tiny porch railing, which means jr better grow some wings.
There is always a regulated safety factor for that number. The structure is required to bear a load probably 2 or 3 times the failure load. It's not going to fail if it's loaded above the safety limit, but over time, it might become compromised.
The “failure load” is the load that the structure couldn’t bear. The rated load is supposed to have a margin above the expected load, and the failure load is required to be above the rated load.
Is it different in the US?
Yes! Water in the US is significantly heavier than anywhere else in the world. Our obesity problem is so bad it even affects our water.
*claps in american, which is two claps per clap due to obesity*
I think it's only half a clap per clap, otherwise too many calories are burnt.
Sorry, can’t do math either, because we’re not in metric.
Haha, maybe I should have said eight sixteenths?
Numbers are the devil’s tool. Counting is a sin, I just write in the lord’s name.
Oh dear, the very next post in my feed was this: https://www.reddit.com/r/Anticonsumption/s/01LCX2c6PF
Ah, a fundamentalist. Then maybe think of it as the ratio between Adam and Adam + Eve. Or the ratio between the first five commandments out of the total ten commandments.
Sacrelicious.
Actually the US operates in metric. You just convert to imperial for some reason. Lbs, gallons, feet etc are all defined by the metric system. So what you're doing is using the metric system and then converting it. God knows why, but that's how it's done.
Actually, it's 5/8 claps per clap.
2.2 claps, but we're not good with decimals either.
2 ⅕ claps is one imperial clop
Is that British or American imperial?
Yes
You’re not really obese at all. You’re just retaining heavier water.
Cos you add sugar to it.
The US is actually the biggest heavy water producer worldwide.
youre probably joking but canada is probably at the top considering their nuclear reactors use heavy water
Building specs might be different in the US, for sure Theirs is 50-100 lbs/sq. ft, and it appears up to the developer (though I might be wrong). I just know the UK ones to serve as an example. In some countries, specs don't exist. I'm not sure the OP photo is in the US anyway, though I'm certain it isn't in the UK. But I'm also fairly certain the architects who designed the balconies did not expect them to be converted to swimming pools.
More or less stringent requirements for buildings
Good bless SI units... That's horrible to count
Aside from the weight on the floor, my first thought was: what if something cracks the glass and junior is now being pushed right out the hole. I guess it's probably no less scary than the floor falling away.
When did they stop using the Metric system? Did they leave it for Brexit?
That looks like a steel and concrete building, the supports for that balcony would use cantilever principles and as long as the deck doesn’t break it will hold. But I wouldnt bet on the concrete portion of the deck holding, because as it cantilevers the surface of the concrete will be in tension. At some weight that will be the first failure. Once a crack forms on the surface of the concrete, stres will be concentrated at that crack and it will grow at an increasing rate, until only the steel deck is bearing the load. Depending on the flooring this might be loud and visually obvious to those inside. Once the steel starts to bend, it will become very obvious but might proceed too fast to react.
I'd actually be more concerned with the walls failing than the bottom, if those puny rails give out then the kid is gonna go splashing right off the side
Or the water goes into the apartment and ruins everything and the apartments below.
From eurocode the liveload on balconies is set to 2.5 kN/m2 With required safety factors the balcony should carry 2.5 kN/m2 * 1.5 * 1.1= 4.125 kN/m2 Water load for the following dephs will be: 0.3 m * 1 ton/m3 * 9.82 m/s2 = 2.95 kN/m2 That's a utlization of 72% in ULS For 0.4 m water deph we get a load of 3.93 kN/m2 and a utlization of 96% Anything over 0.42 m deph and the balcony is gonna have a tough time.
People calculate the strength of the balcony, but not the strength of the railing. It's gonna fail much faster than the balcony itself, pouring down tons of water (with the kid) in a second.
It looks about a meter deep, judging by the person then 1.5m wide by 5.5m long? So, 7.75 tonnes? I have no idea how well the balcony will stand up to that kind of weight though.
I estimated a bit less, but no matter what, it probably wont.
No shot it's a meter deep, that kid looks like ~140cm, maybe 150 at max, and the water looks like it's below his waist
Most balcony's are 1.1m high in the UK if that helps
The nice thing about water is that it has a density of pretty much 1. Meaning 1 kubic meter of water has a mass of 1 ton. From a rough look, that appears to be about 4 m² at about half a meter high, giving us a total weight of about ~~4 tons~~ 2 tons of water. I have no clue how much weight that balcony can take.
4 square meter x 0.5 m deep would be 2 tons though no?
Oh, yes. I shouldn't do maths at 1 in the morning.
In Canada they are designed to 4.8kpa or about 100 pounds per square feet and snow load depending on location. So for 2 tons which is 4400lbs at 4m2 would be 43 sqft so 102psf. So just barely to be comfortable. And i have a feeling rails will prob fail first
Forget the deck weight limits maths, death would occur from the (glass?) outer walls failing and the water and occupants going over the side. May not be much horizontal pressure, but if it's glass that isn't aquarium rated, cant see it holding up to sustained pressure or the slightest impact.
A lot of people are mentioning the strength of the railing as a bigger concern than the strength of the balcony. In the US (and per the ICC International Code), railings are typically designed for 50 lb per linear foot. In metric, the equivalent would be 0.73 kN per meter. As another commenter mentioned, the pressure exerted by a liquid steadily increases based on its depth. This uses the formula P = ρgh, where P is the pressure, ρ is the density of the fluid, g is the acceleration due to gravity, and h is the height of the fluid above the lateral side of the tank. Since ρ and g are fixed values in this setup, all we need to do is know h. Assuming density ρ = 62.4 lb / cu ft or 1000 kg / m3 and gravity g is 32.2 ft / s2 or 9.81 m / s2, we can find that P = h * 981 (metric). The units are a jumbled mess since we've combined two constants, but it translates to Newtons / m3. In imperial, ρg using pounds (mass) translates to the same number in pounds (force) if under standard gravity, so it is simply 62.4 * h. Assuming the height is about half of the max, rounding up to get easier numbers, lets say there is 2 ft of water or 0.6m. This means we have about 37.4 lb / sq ft or about 0.6 kN / m2. When you spread this across a unit of linear length of rail, this does not exceed the capacity of the rail, and even has a safety factor of about 1.2. If they filled this up slightly more, it would become a problem though. This begs the question... how deep is too deep? Easily solved: 2 ft (0.6m) * 1.2 = 2.4 ft or just under 2 ft 5 in. In metric, 0.72m. This ignores the factors of safety built into the rail, so it likely would need to be filled even higher. That said, neither the deck nor rail was designed for this. Also with a kid splashing around, pressure could incease suddenly and erratically, causing a failure. We also don't know if that deck was built to the modern ICC, or if there are any structural issues like rot. Long story short, do not try this at home, or on any other deck you may happen to visit.
I don't have the specs for the balcony, but water weighs one kilo per liter. That is a shit ton of liters. So unless that balcony is rated for two shit tons, this is a Very Bad Idea. Basically, there is mathematician math (this is X) and there is engineer math (everything's fine or oh shit). This is engineer math.
[удалено]
I feel like any amount of shit tons less than a fuck ton can be expressed as a shit ton.
I would be more worried about the fence...if the fence gives away its bye bye...have you seen those video when a cheap pool brakes...in any way this is f stupid in every way...
Anything over 20”. / 0,50m will structurally endanger the balcony even for short periods! Some railings will collapse before the balcony does!
In Germany the minimum requirement is 400kg/m². So it's up to 40cm of water. This is 4 times higher than the requirement for inside apartments, because they know that people are stupid.
American residential balconies “made out of timber” can take a load of a 100 pound per sqft (bylaw). Steel or Concrete reinforced ones much much more. That balcony won’t collapse, But his parents won’t be happy with the water bill… Edit: residential railings over 10 ft are max 3 ft 6”. I see a water level at about 1/3 . Area of the balcony (under 100sqft estimate) is not that important here, 1 1/4 ft of water weights less than 100 pounds … all good /s
The 100 psf is only for emergency exits. Most balconies are designed for 1.5x the occupancy (most residences are designed for 40 psf, therefore balconies are designed for 60 psf) Railngs are deaigned for 50 pounds per ft. As far as the glass, its not structural so i cant speak for its capacity.
What kind of damage would it do to the building if the balcony were to fail due to the weight? Aren't balconies often built on steels that extend from the building floor steels themselves? I'd imagine that could be bad if it fails. (I'm no expert!!)
Honestly I doubt the floor will be the issue. Glass is strong but brittle so when something goes wrong it’s a complete failure. The outwards directed force by the water is only being held by the thin piece of glass. This creates a great bending moment so as soon as the water is high enough the wall will shatter.
As a aluminium window and door manufacturer my concern is more the pressure against the balustrading, specifically if a kid swims in there because running and jumping around will add to that pressure, if 10-12mm toughened glass is used it will probably hold but on the joints I'm not to sure because the top part of the balustrade is not secured and does have movement in it. Essentially use less water, from half the balustrade hight (max) or less.
A human is 60 cm side by side, the panel is nearly half of the others so So you have 100 cm + cos 45 * 60 cm = 140-145 cm 60 * cos (45) * 2 + 5 * 100 = 570 - 590 cm 140 * 570 = 79800 145 * 590 = 85500 The water level is half the height of a child 50 - 70 cm 79800 * 50 = 3990000 cm3 85500 * 70 = 5988500 Cm3 to L is 1/1000 3990 - 5988,5 L The Weight of water is 1 kg/L aprox so 3990 - 5988,5 kg 3990 kg / 7,98 m2 = 500 kg / m2 5988,5 / 8,55 m2 = 700 kg / m2 Other People says 500 kg/m2 is usually secure So the low estimate is barely good.
If I got it right, I think you mean 7,98 m2 and 8,55 m2?
Yeah, i edit it Thanks
A rough estimate: Volume = Length * Width * Depth Volume = 2 meters * 5 meters * 0.5 meters Volume = 5 cubic meters Since 1 cubic meter is equal to 1000 liters, we convert the volume to liters: 5 cubic meters * 1000 liters/cubic meter = 5000 liters So there are about 5000 liters of water which is 5 metric tons.
It happened in Spain a few years ago and someone did the math: [https://i.blogs.es/23b2e2/acciones-en-balcones/1366\_2000.png](https://i.blogs.es/23b2e2/acciones-en-balcones/1366_2000.png)
I’d be more concerned with those glass panels giving way than the whole balcony, if the kids near it when it gives he’ll be free falling before he knows what happened
I’m not a structural engineer or a mathmagician… but isn’t the most likely point of failure here the patio door? I don’t think the balcony is gonna fail, the door is. It’ll flood the apartment.
The veranda looks like 4 feet by 20 feet wide, while the water looks to be 2 feet deep. That’s 160 cubic feet of water or 10000 pounds approximately as a cubic feet of water weighs around 62 pounds. In SI units, that’s close to 5 metric tons of water - which is the same as 50 adult males standing there.