Piano World Home Page Forums Our Most Popular Forums Piano Forum Technical Issue, floor strength.

I am having a room added to my house which will contain, initially, my upright and perhaps later a 6/7 ft grand. The room will have a wooden floor and I am given to understand that a normal wooden floor is designed to take a deadload of 1.5 kN/m² (kN is kilo Newtons) I have no clear idea of what this means. Does anybody happen to know how many kN/m² might be exerted by a grand of this size?

I was looking into finger pressure on keys today. That can run up to 30 N; roughly 3 kg. Your floor will carry about 150 kg per/m2. Pianos like that can weigh up to 400 - 500 kg.

Good evening Withindale, I hope that the weather in Suffolk is not as foul as that affecting SW France today. I have to admit that in technical matters I am a complete dunce and that despite your erudite response I am still not clear whether or not a floor specified at 1.5kN/m² is sufficiently strong to support a grand piano. Any further help that you can give will be much appreciated.

J-C.

Indeed the sun shone on Suffolk today. I've heard it said that if you and I can walk across the room the floor will take a piano. My first post was going to ask how many people might be in the room at a party and how much would they weigh, but I left it out in case someone took offence.

Felicitations.

Hello Jean Claude, put very simply, a 6/7 ft grand roughly needs 4 square meters of space (since 1 m = 3 ft, then the length and width of the piano implies 2 m for both dimensions). So we can divide its approximate mass of 500 kg by 4, which gives (roughly) 125 kg pushing on each of those square meters, so no problem. It's actually more complicated than that, as of course a grand has only three legs, not to mention the additional weight of the surrounding bench, pianist sitting, and especially other heavy furniture around if any.

I say if your new room is built according to construction specs, you will be just fine. It would be another story in an older house like mine where the joists are not so solid, or if there will be several other very heavy objects close to the piano like an enormous 6 ft tall bookcase, etc.

J-C,

I would think that the best bet would be to discuss the issue with your builder.

Picture three people (in the case of a typical grand), holding hands at arms' length, each standing on one heel, where the heels are little bit narrower than cuban heels but not quite as narrow as a stiletto heel, and where said people mass somewhere between well-built and obsese. If you reckon your floor could handle that, then it will probably handle a piano.

Very nicely explained, de cajon
Add to that the fourth person, the piano player, on a four-legged bench...

Normal floors should be fine. However, the party question is well-taken. If a floor won't handle a few people dancing then a grand might add to the problem.

I love the visual!

Although, the small casters on most grands would be more like the pressure of a stiletto heal. Unless, that is, one is using caster cups and then it would be like a Cuban heel.

One must not forget the additional weight of Ricardo Montelban atop an artist bench upholstered in Corinthian leather.



Is a photo available?

maurus - great minds think alike!

Hi Jean Claude,

Marty's answer is most correct.
The load limit will not be exceeded on a distributed basis (considering the large area the piano covers), but will certainly be exceed just considering the area under the wheels or caster cups, so that needs to be clarified with your builder.

Best wishes-

Thank you all for your reassuring responses. I must say in passing that if a piano weighs about 500kg then each of our hand-holding party-goers will weigh, on average, just short of 170kg (for those of you who do not yet benefit from the Napoleonic system of weights, that is about 26 stones) I earnestly hope that they will not take it into their heads to start any sort of one-legged dance, not because of any concerns for the integrity of my floor but purely on aesthetic grounds.

J-C.

Reinforce the floor if you are really worried. When we built our addition, I had the builder put double the I beams under the section of the room where we would put the piano, and double thickness plywood. My 7' M & H is about as heavy as most other brands' 9 footers.

I have total peace of mind.

I am not a construction engineer so the following is strictly a simplistic novice application of Physics to the complex computations of Load Distribution. It may help you explain your concerns to the engineer and ask him/her to provide you with a convincing design that mitigates your concern.

1 Newton (N) is 0.101972 kgf.
Kilo (k) = 1000.

1.5 kN/m-2 = 1.5 x 1000 x 0.101972 kgf / m-2 = 152.96 kgf / m-2.

Let us assume that the 152.96 kgf is distributed evenly over 1 square meter, then we have approx. 0.0153 kgf / cm-2.

Let us now apply this to a hypothetical piano:

1. Steinway Model B, 211 cm, 345 kg (kgf).
2. Length is 211cm, width is 148cm.
3. Approx. area is 31228 cm-2 or 3.12 m-2 (square meters).
4. Given shape of a grand, it is possible this area is evenly distributed under each foot.

Let us assume, simplistically, that the piano's weight is distributed to three legs evenly; then, each leg of the Model B will exert 115 kgf down through the wheel to the floor.


Exactly how this load is distributed by Building Engineering is beyond my expertise.


If this force is evenly distributed to a square meter, then the the floor deadload specification of 152.96 kgf / m-2 is larger than the piano load of 115-kgf / m-2.

For the sake of this discussion, let us further assume, simplistically, that the contact surface of the wheel is 5mm wide by 10 cm long yielding a contact surface area of 5 square centimeter (cm-2).

This means we have a theoretical 115-kgf down through 5 cm-2 of contact surface, or 23 kgf / cm-2.

Each contact point of the Model D is exerting a deadload force of 23 kgf / cm-2 on the floor.

If this force is not evenly distributed to a square meter, then the piano load of 23 kgf / cm-2 is much much larger than the floor deadload specification of 0.0153 kgf / cm-2.

Again, exactly how this load is distributed by Building Engineering is beyond my expertise. Hopefully, this can help you start a conversation with the Building Engineer.

Good luck and I hope this is useful.

Really gang - Tell the contractor that you are contemplating the purchase of a grand piano and want to make sure the floor is sturdy enough.

It's new construction! It's a no brainer.

In an older building, if there is a question, hire a structural engineer to do an inspection.

How do you factor in the effects of sound vibration?

Unfortunately, our experience in California says otherwise .

Forgive me but just like in piano, the experts often have "little patience" with the perceived novice and they often wave us off too soon. It pays to listen to us.

In our case, a very good contractor ignored our specifications about an in-home IT room. It is a real IT room with real IT wiring, cooling and fire-suppresant requirements, but he ignored all our questions and waved us off.

I finally withheld the first payment before design commenced and wouldn't give him the signed contract until he listened and answered our questions; however stupid they might be in his eyes.

He then said that he thought we were just talking about a couple of computers sitting on a desk. The design for that would have been trivial compared to our actual needs.

I think the consumer needs to be as INFORMED as possible. This is true in piano shopping and also true in home construction and everything else.

CHeers!

Lordy

Time to move on to "Technical Issue #2, acoustics"?