How much weight can bedroom floor take

greenface2

you want to build a hot tub don't ya ???? 

Norman_Castle

greatcrested said:

,...........

It all started when a neighbour kept turning up with cake...

grumbler

Ajackspade said:

I spent alot of time researching this question, "how much weight can upper/raised timber joist floor take" ?
The only answers I could find was that ( and in-line with UK building regulations )  the floors should be designed to take a load of 150kg/m2 spread over the entire floor.  
However this is an unsatisfactory answer , because does it mean 2 x 100kg people standing next to each will cause the floor to fail? Clearly not, so the specification of  spread over the floor is not a useful metric in my opinion.

Ideally I need to know the maximum allowable weight  over a square meter taken at mid span.

The internet was generally very poor at answering this question.

Assuming 60cm distance between  joists, 150kg/m2 means 90kg/m uniform load for each joist.

The same deflection in the midpoint of the joist will be if you apply 0.625 of the total load in the midpoint of the joist instead of spreading it.

weeg

The code states that domestic floors must be designed to carry a UDL of 1.5kN/m2 over the entire floor OR a point load of 2.0kN at any point (there's your 2 people in 1 sq m covered). An most cases the 1.5 UDL is the more onerous.
Realistically though, your floor will be able to take more than this without failing, as there is also a deflection limit of 14mm, or span/333, and this is the most common mode of 'failure', by which I mean I floor failing to conform to the BSs. I's also note that for ULS (or failure type states) these figures have a load factor of 1.5 applied. SLS ( or deflection) is calculated using unfactored loads. These are the current BS EN 1991-1-1 values, or course. The previous code BS5268 used 1.6 for live loads.

And no, if you put 1500kg in one room, it wouldn't collapse. I've absolutely put more than that in upstairs rooms. (Pallets of plasterboard, specifically, although we stack them away from midspan)

Of course, I'm assuming your house was built properly. 

If you don't believe that the - as you admit- readily available figures are true, then the only option is to lift the floorboards, measure the joist spacings and sizes, check the timber grade, and moisture levels in the timber and run a back analysis. Or maybe consider than structural engineers know how to design houses.

Belenus

greenface2 said:

you want to build a hot tub don't ya ???? 

Maybe a home water birth pool.

As in the Worst Week of My Life.

GDB2222

@weeg I'd have thought that a lot less than 14mm droop in the ceiling below would be very noticeable, with cracks in the plaster?

Also, does the timber tend to bend more over time? So, what starts as a small deflection steadily gets larger?

I doubt that the failure mode is that the whole thing collapses very often? People in the room below would get alarmed long before it actually gives way. 

Of course if you load the floor up with a gigantic hydroponic cannabis factory that might be different.

weeg

GDB2222 said:

@weeg I'd have thought that a lot less than 14mm droop in the ceiling below would be very noticeable, with cracks in the plaster?

Also, does the timber tend to bend more over time? So, what starts as a small deflection steadily gets larger?

I doubt that the failure mode is that the whole thing collapses very often? People in the room below would get alarmed long before it actually gives way. 

Of course if you load the floor up with a gigantic hydroponic cannabis factory that might be different.

It's much less noticable than you would think. It's also not that common - because you'd have to really load the floor to the max allowable, which doesn't happen that much in housing. You get a little bit of creep over time, but timber is pretty elastic, so mostly the floor bounces back when you remove the weight. The whole thing collapses is indeed rare. That limit has been in place for decades (since the 80s, I think), if anything it's more onerous now.

There's a line between cost and robustness, and developers like to sit as close to the line as they can, so the creakiness of new builds can be surprising if you've never lived in one before, but that's usually all it is - a bit of local creakiness. Of course, there are instances when people mess it up  - either designers or builders, or lack of communication between the two.

jackspade

weeg said:

The code states that domestic floors must be designed to carry a UDL of 1.5kN/m2 over the entire floor OR a point load of 2.0kN at any point (there's your 2 people in 1 sq m covered). An most cases the 1.5 UDL is the more onerous.
Realistically though, your floor will be able to take more than this without failing, as there is also a deflection limit of 14mm, or span/333, and this is the most common mode of 'failure', by which I mean I floor failing to conform to the BSs. I's also note that for ULS (or failure type states) these figures have a load factor of 1.5 applied. SLS ( or deflection) is calculated using unfactored loads. These are the current BS EN 1991-1-1 values, or course. The previous code BS5268 used 1.6 for live loads.

And no, if you put 1500kg in one room, it wouldn't collapse. I've absolutely put more than that in upstairs rooms. (Pallets of plasterboard, specifically, although we stack them away from midspan)

Of course, I'm assuming your house was built properly. 

If you don't believe that the - as you admit- readily available figures are true, then the only option is to lift the floorboards, measure the joist spacings and sizes, check the timber grade, and moisture levels in the timber and run a back analysis. Or maybe consider than structural engineers know how to design houses.

Thanks much appreciated.
Basically the answer im looking for is , take a standard upstairs bedroom in a UK house built in last 30 years , what is the maximum weight placed at mid-span ( over 1 meter squared ) that would be close to acceptable limit?  I understand its not an easy question to answer doing pure calculations and might be the sort of question that only a real life simulation could answer.  I dont know.

Whats your opinion

weeg

jackspade said:

weeg said:

The code states that domestic floors must be designed to carry a UDL of 1.5kN/m2 over the entire floor OR a point load of 2.0kN at any point (there's your 2 people in 1 sq m covered). An most cases the 1.5 UDL is the more onerous.
Realistically though, your floor will be able to take more than this without failing, as there is also a deflection limit of 14mm, or span/333, and this is the most common mode of 'failure', by which I mean I floor failing to conform to the BSs. I's also note that for ULS (or failure type states) these figures have a load factor of 1.5 applied. SLS ( or deflection) is calculated using unfactored loads. These are the current BS EN 1991-1-1 values, or course. The previous code BS5268 used 1.6 for live loads.

And no, if you put 1500kg in one room, it wouldn't collapse. I've absolutely put more than that in upstairs rooms. (Pallets of plasterboard, specifically, although we stack them away from midspan)

Of course, I'm assuming your house was built properly. 

If you don't believe that the - as you admit- readily available figures are true, then the only option is to lift the floorboards, measure the joist spacings and sizes, check the timber grade, and moisture levels in the timber and run a back analysis. Or maybe consider than structural engineers know how to design houses.

Thanks much appreciated.
Basically the answer im looking for is , take a standard upstairs bedroom in a UK house built in last 30 years , what is the maximum weight placed at mid-span ( over 1 meter squared ) that would be close to acceptable limit?  I understand its not an easy question to answer doing pure calculations and might be the sort of question that only a real life simulation could answer.  I dont know.

Whats your opinion

It's a very easy question to answer if you know exactly what the floor construction is. But you don't know that, so I would strongly advise not exceeding the design loadings. Of course, if you gave us an idea of WHY you are asking this question, we might be able to tell you if it's a terrible idea.

There is no such thing as a standard upstairs bedroom. Houses/ housetypes are all individually designed.