Even an estate home with neighbours eight feet away will have noise. You’ll still hear your neighbours barbecuing in the back yard, emergency vehicle sirens, or airplanes passing overhead. Anywhere you live, you’re going to have some type of noise.

Everyone has a different tolerance to noise. What you find tolerable may drive other people crazy. The challenge for homebuilders is to minimize the sound between units as much as possible so that everybody wins.

Walter Neufeld, General Manager of Stonecroft explains, “We’re quite concerned with sound attenuation in our projects. It’s very irritating for homeowners. They have no way of knowing after they’ve looked at a place if the sound attenuation is sufficient. There are some procedures for proper sound attenuation. If they’re followed quite strictly, you will not have problems with sound transmission between units or you’ll at least have acceptable levels.” 

Tim Huxley is the Project Manager for The National. “Typically, in a concrete building, you’ll have a concrete floor structure. The walls between the suites – the party walls – will be two steel stud walls parallel with each other. The two wall structures are built with a one-inch air gap in the middle. Most concrete buildings today have steel studs in them. You stagger the studs in the two walls so the two walls never have a chance to touch. That’s the whole trick – the air gap that runs down the middle does not allow the sound to travel from one side of the wall to the other. Then once the walls are framed, they are both stuffed with insulation.”

Besides killing sound, this type of wall structure also acts as a firebreak between the suites.

“In the National, we are putting in double drywall on one side, in one suite, and on the other side of the party wall, one sheet of drywall,” adds Huxley. “By not duplicating or mirroring the two walls, you actually confuse sound even more.

“The other kind of noise people worry about is the transfer from above through your ceiling. In the case of hardwood floors, you must put a sound mat under the floor, so you cannot get a physical transfer of sound from the hardwood to the concrete.”

In a concert hall, two shells are constructed – an exterior shell keeps sound out and an interior shell keeps sound in. It’s a principal similarly used in multifamily construction. An acoustic shell is built within the building and is isolated from the rest of the building itself.

According to Cardel Lifestyles sound expert Brad Remington, “Traditional homes are built out of 2 x 8 or 2 x 10 lumber, depending on the span across the floors. For our “silent floor,” on top is a 2 x 2, a sub-floor, then a 2 x 2 to form a little truss. That’s basically 12 inches in depth and spans the units of our condominiums from party wall to party wall. We’re trying to isolate any airborne noise going right through and impact that noise.”

Whether the building is wood-frame construction or concrete, either way, you may still hear the dropped silverware from above. While extra layers of materials absorb sound, bat insulation is also used to fill cavities and help cushion sound.

There are minimum standards a builder must apply. The Sound Transmission Classification (STC) is rated much like a Richter scale, which means a seven is ten times greater than six on the scale. So if a building has an STC rating of 50 that would make it ten times the rating of 40. The Alberta Building Code minimum STC rating is 50.

A bead of acoustic caulking, 2 x 4 or 2 x 2 sheets of lumber, strips of resilient channels, air gaps, concrete, or foam – every builder does it differently. There are pre-tested assemblies a builder will choose upon based on its own sound attenuation standards. The architect reviews the drawings of the assembly and suggests a method for the builder to use. With a tile or hardwood floor, extra measures are usually added for better sound attenuation.

Moving a chair across hardwood floor, stomping around in steel-toed boots, and kids bouncing a basketball – it’s pretty difficult to stop the vibration from that kind of foot traffic in any situation. Builders will do their best to lessen the impact of sound transfer, but a considerate neighbour is ultimately the best defense.