Why You Should Never Put A Pool On Your Terrace, Explained With Structural Calculations By An Architect

Why you should never put a pool on your terrace, explained with structural calculations by an architect

With the arrival of heat and summer, many people may wonder: Can I put a pool on my terrace or balcony?

The short answer: NO.

Thank you for reading. Like and follow me for more architecture tips.

The long answer: come with me on this exciting journey of loads and structural calculations

Why can’t I put a pool on my terrace?

The fundamental reason why you should not put a pool on a terrace is because it was not designed to support your weight. What happens is that with this answer we do not get an idea of how much more weight we are overloading the structure.

Let’s do some quick numbers. A circular inflatable pool 3 meters in diameter and 76 centimeters high like this one from Amazon has an advertised capacity of 3,600 liters if it is 90% filled (it is not completely cylindrical, otherwise it would be 4,836 liters).

Why can't I put a pool on my terrace

Knowing that the density of water is approximately one kilogram per liter, which is 3,600 kg of mass ( 3.5 tons, which is more impressive) spread over an area of ​​7.07 m2, which comes out to 509 kg/m2.

Do you know what is the calculation overload of the Technical Building Code (page 9.) for a terrace in a residential building? 200kg/m2. (, 2 kN/m2 because they are loads, not masses, but I have changed the units -and rounded- so that it is understood).

In other words, with a pool of that size, we are making the structure support more than double the load for which it was designed.

This also applies to smaller pools, because it is a matter of weight per area. Any pool that is filled to 50 centimeters will have a mass of 500 kg/m2 and, therefore, will entail an overload of two and a half times what is expected.

But what about the safety factors or the redistribution of burdens?

Safety factors are indeed fed into the calculations, but those are there for, well, safety. In case the materials do not behave as expected, to assume construction imperfections or defects, irregular load distributions, loss of bearing capacity due to exhaustion… Furthermore, they are never greater than two. Even with this coefficient, we are taking the floor to the limit (what is under the terrace floor) and even the beams and pillars.

On the other hand, it must also be considered that the slabs have a compression layer that redistributes the load so that it is assumed by a greater part of the structure, but this layer is more designed to distribute point loads, such as a shelf or a bathtub. Speaking of bathtubs, which are mentioned a lot in these cases: filling the bathtub is usually about 200 liters of water (aka, 200 kg), a much smaller mass that can also be easily distributed, nothing comparable to 3.5 tons. of water.

So, what inflatable pool can I put on my terrace?

So, what inflatable pool can I put on my terrace

Continuing with the numbers that we have done before, theoretically, we could put any pool on the terrace as long as we did not fill it with more than 20 cm (that gives the 2 kN/m2 maximum load). But of course, that is a span of water. And there, in addition, it is necessary to add to the calculation the occupants of the pool (75 kg per adult), because we cannot consider them submerged in a span of water.

So, taking that into account, the biggest pool that we should put on the terrace is a small one for babies and fill it up to a maximum height of 20 centimeters.

That is already 3 kN/m2 (300 kg/m2 to understand each other), 50% more than the calculation overload. What happens is that, in this case, the compression layer is more effective at redistributing the load, so for calculation purposes, we can consider that it is distributed over a larger area than the one occupied by the pool. Even so, it is appropriate not to fill them beyond 20 centimeters, because the pool is not the only thing on a terrace.

Well, my brother-in-law has one on his terrace and it hasn’t fallen

And a man who smoked like a Carter lived to be 105 years old.

The terraces with swimming pools fall. Happens.

So no swimming pools on the terraces and the balconies. Please. If you want to cool off, a hose or, at most, a “bathtub” or its equivalent volume on the terrace.