Floors/Ceilings

Floor Isolation

Floating floor over concrete

“I am going to build a wooden frame and put insulation in it and plywood on top for my home studio recording room.
Everyone is doing it…Isn’t this a real floating floor?”

floated floor

I have seen this attempt to make a floating floor before. And some have wrestled sand into the frame as a means to add mass. The limp mass provided by the sand is effective in this case.

The sand is limp mass and certainly far more mass than insulation. You control the resonant frequency of the cavities and damp the flooring with either process.

These are important things to do.

There is a standard drum riser that uses owens corning 703 as a means to damp the vibrations from the drums to the rest of the home studio area. It simply decouples as best as possible, so it is not a true floating floor in this respect.

First, an existing Earth damped concrete floor has very high isolation ability. Hell it has the World on the other side of it, so where the thinking came from that a floating floor could be developed on an existing slab with no ramifications in respect to the existing structure is far beyond me.

“Planes, trains, cars, windmills, span bridges, structures, roads, cellular antennas, high rise buildings and the list goes on and on and on, all have the same one thing in common. Vibration is the enemy.”

“Either by seismic or regional weather conditions that move the object, vibration will be a part of the life span of the item in question.”

So we stop vibration by moving the object farther away and when distance isn’t enough we add mass and when mass is not enough we decouple the object and when decoupling is not enough we damp the object.

The natural resonance of anything will allow vibration at that natural frequency to pass thru the object like it did not exist. It is a misunderstanding that sound is moving from one side of a wall to the other. Sound is vibration and vibration is what is moving from one side of a wall to the other.

If it were simply sound then a closed door would stop it. But it isn’t sound it is vibration and the natural resonance of every piece of material involved in anything will either let parts of the vibration pass or it will stop other parts of it.

Earth damped concrete floors have a very low center frequency meaning it will take a vibration at least at or lower than this center or natural frequency to excite/vibrate the concrete slab.

Mass Law predicts that for ever doubling of mass you can expect to ceate a 5 to 6 point jump in the STC or sound transmission class value.

Normal weight concrete weighs about 4000 lb. per cubic yard. There are 27 cubic feet in a cubic yard.
A cubic foot of concrete weighs around 150 pounds. So in order to double that you would have to be able to support another 150 pounds per every cubic foot placed on the existing slab.

So how can it be that a lightweight wooden framed, insulation damped plywood sheathed membrane is even considered as a logical method to develop an even lower transmission loss capable, mass/spring/mass floating floor?

Floor Isolation

STC/IIC Sound Test Data, Concrete Structural Deck
Airborne Sound Transmission Loss, Impact Sound Transmission and Special Impact Tests Measurements Performed on One(1)

Floor Assembly:

Investigation of the sound isolation of concrete slab floors
“The talks studios in the basement of Broadcasting House Extension were mounted on rubber pads as a protection against noise and vibration from the Bakerloo line which passes very close to the building. The isolation achieved, however, was less than the calculated figures and, although a margin of safety was allowed, the noise level in one studio proved to be higher than the maximum acceptable.”


Detailed Report for Consortium on Fire Resistance and Sound Insulation
of Floors: Sound Transmission and Impact Insulation Data in 1/3 Octave Bands
Summary Report for Consortium on Fire Resistance and Sound Insulation of Floors: Sound Transmission and Impact Insulation Data”

Noise and Vibration Control “This manual provides qualified designers the criteria and guidance required for design and construction of those features related to noise and vibration control of mechanical equipment systems most commonly encountered in military facilities. “

Study of Poured-In-Place Concrete Wall ASSEMBLIES in Coastal British Columbia
Examine several specific aspects of construction practices (including exterior coatings, concrete mix, crack control and joint detailing) that impact the performance characteristics of poured-in-place concrete wall assemblies.

Floating floor over concrete

Is a Floating Floor Right For You? Answer: Probably NOT
“One of the most common assumptions people make about studio designs is that a floating floor is necessary to achieve the necessary amount of isolation (a.k.a soundproofing). “

Kinetics: STC/IIC Test Data: Floor and Ceiling Products
“Kinetics Sound Test Data for Architectural Products Sound Transmission Class (STC) and Impact Insulation Class (IIC)”

Floor stc values

Basement Insulation System
“Q: What are the Sound Transmission Class (STC) ratings for concrete and masonry walls? “

BSI-003: Concrete Floor Problems
“Moisture is involved in most building problems. The most serious tend to be structural damage due to wood decay, unhealthy fungal growth, corrosion, freeze-thaw, and damage to moisture sensitive interior finishes. Avoiding these problems requires an understanding of moisture, the nature of materials, and how it interacts with materials”

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