Weight Limit for a Concrete Reinforced Floor?

[xohaib]

Hi,

Here is an interesting question for civil engineers. I have installed a round 15 feet diameter & 4 feet deep swimming pool that holds about 4,400 gallons of water at my back terrace on 1st floor. My house is newly built, constructed this year in January, the floor is made of about 10 inch thick steel reinforced concrete. The location where i have placed the pool is supported by 9" thick walls under it. While filling the pool i started to get worried as the weight of the water is going to be approx. 16,632 Kg as 1 gallon of water weighs 3.78 Kg. Right now the pool is only 1 feet filled. I am confused whether it is safe to load the concrete slab with 16k+ Kgs. Is there any formula i can calculate the load bearing capacity of the concrete slab? Or what is the max weight an ordinary floor can sustain?

Below is the diagram of the pool area.

Thanks, Zohaib

[waqar19]

@fazalwahab11375 can guide you better.
Also post the detail of foundation.
e.g

[fazalwahab11375]

Have you consulted any structural engineer or just did everything on your own? We always realize and get confused about things when we have already done it especially construction. Share structural cross sections and pictures if you have.
Is wall designed/ constructed as a load bearing wall?
Is this a brick wall or reinforced concrete wall?
When you filled the tank, did you see any deflections?
What is underneath the pool area? Any occupied space?
How is the quality of concrete? Any compression data?

Its not the load what a slab can take.. I am concerned about the walls underneath . You needed formulas at time of design. We can come up with solution if you share more data.

Hi,

Here is an interesting question for civil engineers. I have installed a round 15 feet diameter & 4 feet deep swimming pool that holds about 4,400 gallons of water at my back terrace on 1st floor. My house is newly built, constructed this year in January, the floor is made of about 10 inch thick steel reinforced concrete. The location where i have placed the pool is supported by 9" thick walls under it. While filling the pool i started to get worried as the weight of the water is going to be approx. 16,632 Kg as 1 gallon of water weighs 3.78 Kg. Right now the pool is only 1 feet filled. I am confused whether it is safe to load the concrete slab with 16k+ Kgs. Is there any formula i can calculate the load bearing capacity of the concrete slab? Or what is the max weight an ordinary floor can sustain?

Below is the diagram of the pool area.

Thanks, Zohaib

[VCheng]

Whatever you design, how can you be sure it will be built according to specifications?

Have you consulted any structural engineer or just did everything on your own? We always realize and get confused about things when we have already done it especially construction. Share structural cross sections and pictures if you have.
Is wall designed/ constructed as a load bearing wall?
Is this a brick wall or reinforced concrete wall?
When you filled the tank, did you see any deflections?
What is underneath the pool area? Any occupied space?
How is the quality of concrete? Any compression data?

Its not the load what a slab can take.. I am concerned about the walls underneath . You needed formulas at time of design. We can come up with solution if you share more data.

[xohaib]

@fazalwahab11375

Thanks for your reply.

Unfortunately i don't have any constructional details as we bought this house from a builder, and its practically not possible for me to contact him and get the details. The house was not built considering that a swimming pool will be placed on the top, however its a single story house with one room at the 1st floor at front and all the area at back side is the covered terrace.

Do you think this much load is really harmful for the concrete slab?
Can you please tell what is the average load bearing capacity of an ordinary concrete slab?

[qwertypoiu]

Where is the house located ? As per rules all the detailed plans are submitted in society office. If its Dha or some new scheme it is easy to get them.

[waqar19]

@fazalwahab11375

Thanks for your reply.

Unfortunately i don't have any constructional details as we bought this house from a builder, and its practically not possible for me to contact him and get the details. The house was not built considering that a swimming pool will be placed on the top, however its a single story house with one room at the 1st floor at front and all the area at back side is the covered terrace.

Do you think this much load is really harmful for the concrete slab?
Can you please tell what is the average load bearing capacity of an ordinary concrete slab?

its not only about concrete slab. the load will be deposited to brick walls and foundations underneath. without knowing details of structure, its risky!

[fazalwahab11375]

its not only about concrete slab. the load will be deposited to brick walls and foundations underneath. without knowing details of structure, its risky!

Technically I will not go for a brick wall to take such loads. I will go for Concrete columns with drop panels to withhold the extra load on the slab . Now that's not possible.
You have changed the utilization of the structure now. There is no average load. An engineer design the slab looking at the use, dead and live loads and with factor of safety in place. You can have a 10" slab and a heavy truck load can pass over it. You can have a 12" slab and even a car would not be an appropriate load. Engineer design the slab or any other structural segment on basis of concrete strength, size of rebar, spacing or rebar/steel. Your terrace slab was designed for a light foot traffic and never ever for a pool. It was not designed to take 16000Kgs of dynamic load. In other words think about gathering 200 people on your terrace each weighing 80kg on average and concentrating them within 176 square feet area. Do that look safe?No it will over load the slab.

You need to consult a local structural engineers NOT an Architect. These things need visual inspection. If you dont have drawings an engineer on site will be able to estimate what is required / is it safe or appropriate. In my opinion I would not fill up the pool until you get the structural evaluated. Being professional myself I dont and never make recommendations until I see things in black and white.

[fazalwahab11375]

We can always increase the load capacity of the slab or columns if needed. Carbon fiber external applied composites are the answer but even for designing that we need to estimate current structural design. [I have done numerous projects with such technology and we are using it here to strengthen bridges. I can get you in touch with experts in Lahore who do same, if you want to go that way but it will cost you some money]

[butwhy]

Whatever you design, how can you be sure it will be built according to specifications?

You can't be sure....So you increase tolerances in design and "overbuild"...

[VCheng]

You can't be sure....So you increase tolerances in design and "overbuild"...

Sure, that works only up to a point.

[zia1288]

Structural engineer will inspect and calculate the loads for you. Most probably by using sap. You should have consulted before construction. By the way what is under the pool area?

[xohaib]

Structural engineer will inspect and calculate the loads for you. Most probably by using sap. You should have consulted before construction. By the way what is under the pool area?

Zia, The pool is made up of metal frame, i bought it from the market. Pool itself has no weight, its less than 50Kg. There are four walls under the pool as shown in the above diagram.

[xohaib]

Have you consulted any structural engineer or just did everything on your own? We always realize and get confused about things when we have already done it especially construction. Share structural cross sections and pictures if you have.
Is wall designed/ constructed as a load bearing wall?
Is this a brick wall or reinforced concrete wall?
When you filled the tank, did you see any deflections?
What is underneath the pool area? Any occupied space?
How is the quality of concrete? Any compression data?

Its not the load what a slab can take.. I am concerned about the walls underneath . You needed formulas at time of design. We can come up with solution if you share more data.

@ fazalwahab11375

Is wall designed/ constructed as a load bearing wall? YES
Is this a brick wall or reinforced concrete wall? Brick Wall
When you filled the tank, did you see any deflections? NO
What is underneath the pool area? Any occupied space? There are four walls intersecting each other and pool is exactly place at its center.
How is the quality of concrete? Any compression data? I don't have any data, but i am sure that the construction quality is A+

[xohaib]

We can always increase the load capacity of the slab or columns if needed. Carbon fiber external applied composites are the answer but even for designing that we need to estimate current structural design. [I have done numerous projects with such technology and we are using it here to strengthen bridges. I can get you in touch with experts in Lahore who do same, if you want to go that way but it will cost you some money]

@fazalwahab11375

How much the expert visit will cost?

I have calculated the weight bearing capacity of the slab and the walls on my own, may be i am going in the wrong direction but this is what i came up with. Doing a bit of reverse engineering.

Few Facts:

> The foundations of this house is constructed for double story construction for future expansion.
> The pool is placed on the back terrace, and there are four walls under it.
> Slab is RCC

Lets replace the pool weight with the weight of building on 1st floor in that area. Suppose we construct 4 walls on the back terrace with dimensions 7.5'(2.3m) x 10'(3m) exactly on the top of the ground floor walls, where the pool is placed right now.

Assuming the no. of bricks required per square meter is 120 for double brick wall, total bricks required is 2.3x3x120 = 828
For four walls same dimensions no. of bricks = 828 x 4 = 3,312
Assuming weight of each brick is 2.5 Kg
Total weight of all bricks = 2.5 x 3312 = 8,280 Kgs
Adding assume weight of plaster = 1,000 Kg
Total weight of walls including bricks & plaster = 8,280 + 1,000 = 9,280 Kgs (A)

Now lets calculate the weight of the slab of the 2nd floor.
Considering the weight of the slab is evenly distributed on all the walls, i am going to calculate the approx. weight of the slab just above the walls and not for the whole room.

Area of the portion of slab for 2nd floor is 15' x 15' = 225 sq. ft
Assuming the weight of concrete block per sq. ft with height 8" = 40.21 kgs using http://www.calculator.net/concrete-calculator.html
Total weight of the concrete slab = 225 * 50 = 9,047.25 Kgs (B)
* Not including brick floor and other miscellaneous weights

Total weight A + B = 9,280 + 9,047 = 18,327 Kgs.

So this is the total weight for which the foundations, walls and the slab on 1st floor is designed.

Comparing with the weight of swimming pool with water is 16,500 Kgs. I still have an approx. 2,000 Kgs cushion for overloading.

What do you think?

[butwhy]

@fazalwahab11375

How much the expert visit will cost?

I have calculated the weight bearing capacity of the slab and the walls on my own, may be i am going in the wrong direction but this is what i came up with. Doing a bit of reverse engineering.

Few Facts:

> The foundations of this house is constructed for double story construction for future expansion.
> The pool is placed on the back terrace, and there are four walls under it.
> Slab is RCC

Lets replace the pool weight with the weight of building on 1st floor in that area. Suppose we construct 4 walls on the back terrace with dimensions 7.5'(2.3m) x 10'(3m) exactly on the top of the ground floor walls, where the pool is placed right now.

Assuming the no. of bricks required per square meter is 120 for double brick wall, total bricks required is 2.3x3x120 = 828
For four walls same dimensions no. of bricks = 828 x 4 = 3,312
Assuming weight of each brick is 2.5 Kg
Total weight of all bricks = 2.5 x 3312 = 8,280 Kgs
Adding assume weight of plaster = 1,000 Kg
Total weight of walls including bricks & plaster = 8,280 + 1,000 = 9,280 Kgs (A)

Now lets calculate the weight of the slab of the 2nd floor.
Considering the weight of the slab is evenly distributed on all the walls, i am going to calculate the approx. weight of the slab just above the walls and not for the whole room.

Area of the portion of slab for 2nd floor is 15' x 15' = 225 sq. ft
Assuming the weight of concrete block per sq. ft with height 8" = 40.21 kgs using http://www.calculator.net/concrete-calculator.html
Total weight of the concrete slab = 225 * 50 = 9,047.25 Kgs (B)
* Not including brick floor and other miscellaneous weights

Total weight A + B = 9,280 + 9,047 = 18,327 Kgs.

So this is the total weight for which the foundations, walls and the slab on 1st floor is designed.

Comparing with the weight of swimming pool with water is 16,500 Kgs. I still have an approx. 2,000 Kgs cushion for overloading.

What do you think?

Buddy, the thing is, you have ~37,000 extra pounds (for the water alone from your own figures) resting on around 22sq.ft of wall that will be taking the load (we don't know how well the slab is able to transfer the load on to the rest of the walls on which the pool is not directly on top, so we take just the wall area). So we get additional ~1,700 psi that will be placed on the wall in orange highlighted area.

The problem may not be that much of the slab, but mainly the wall and its compressive strength.

[butwhy]

Sure, that works only up to a point.

then the builder has sit in 40 degree heat and make sure nothing major is going wrong. lol...

[VCheng]

then the builder has sit in 40 degree heat and make sure nothing major is going wrong. lol...

It is too late for that now, since the construction was completed a long time ago. Now the issue is whether reinforcement is needed to use the pool safely or not.

[fazalwahab11375]

I wish these numbers were that easy. Lets assume for a second.. both walls and slab are fine.. the load need to transfer via wall to ground.. what you did under the wall? What is size of footings? You need to transfer the load ? What you did there?

Now go back again. Concrete is good in compression not in tension. Once you load a slab the deflection starts. You need a tension member in slab to transfer the load.. what that is? Your steel. Here comes size of bar and spacing. Concrete is poor in tension and will not transfer moments until you have adequate steel in it.

I am not saying your slab is weak to take this load. But the point is your slab is not designed for such loads and overtime you will or might see problems. You need to contact a structural engineer for evaluation. He will make recommendations.

[VCheng]

I wish these numbers were that easy. Lets assume for a second.. both walls and slab are fine.. the load need to transfer via wall to ground.. what you did under the wall? What is size of footings? You need to transfer the load ? What you did there?

Now go back again. Concrete is good in compression not in tension. Once you load a slab the deflection starts. You need a tension member in slab to transfer the load.. what that is? Your steel. Here comes size of bar and spacing. Concrete is poor in tension and will not transfer moments until you have adequate steel in it.

I am not saying your slab is weak to take this load. But the point is your slab is not designed for such loads and overtime you will or might see problems. You need to contact a structural engineer for evaluation. He will make recommendations.

May be it is time to fill the pool and see what happens?