For one thing, should a multi family building be totally silent? In other words should you ever hear anything from above, below or around? Often one of the problems is a person’s expectations can be based upon faulty information or a preconceived idea. Making a sound proof building is difficult and costly.

To explain how sound travels will help know what questions need to be asked when determining the sound attenuation of a building’s floors and walls.

There are 3 common things people desire to have. Price, quality and service, you can only pick two. You can’t have low price and excellent service and quality. Often time we are willing to forgo one of these to get a better price, or we want these and are willing to pay more. That is often true with sound as well. In this case we could say price, quality and quiet. To get a quiet building you will probably have to pay more. Its what is commonly referred to as value and it is subjective.

That being said, what is a reasonably quiet living area? The building code actually stipulates minimum standards for sound attenuation in multi family dwelling units. These are rated by the amount of sound you can hear from adjoining hallways and rooms. However, that’s only part of the issue. Lets discuss the various types of sound.

The building code references what is called STC sound or in laymen’s terms airborne sound. This is the sound from sources such as people speaking, radios, traffic driving by and the like. STC stands for Sound Transmission Class and is measured in decibels. The easiest way to reduce sound of this type from traveling from one place to another is to use a large mass that will stop sound vibrations, or to use materials that will absorb sound vibrations.

A concrete wall will stop sound - thick carpet and underlay will absorb sound. That is, sound from talking or radios. It is the STC or airborne sound. That minimum number the building code stipulates is 50 and 55 if near an elevator. Most builders these days are building to a much higher standard. That being said however, at 50 you may still hear the occasional conversation or radio. Going to a 60 or 62 rating actually doubles the sound reduction, but  - there are other sources of sound.

Impact sound is another source recognized by builders, yet there is currently no minimum building code requirement. IIC or Impact Insulation Class is a way of measuring the impact sound from walking, tapping, mechanical vibrations such as elevator pumps etc. Materials that work well to sound proof for the airborne or STC, won’t necessarily protect from impact noise.

For instance, 6” of concrete stops airborne sound very well, yet for impact sound, concrete is a very poor insulator. According to published CMHC guidelines, a concrete floor insulates against airborne sound and has a rating of STC 52. For impact sound however, the rating is only IIC 25. Yet add carpet to the same floor and it increases to IIC 86! The problem is that you won’t be putting carpet throughout your whole house.

A builder must do is find economical ways to allow the installation of tile, hardwood, or vinyl flooring and maintain good sound protection for the people living above.

To accomplish this, the wall or floor must be designed as a system, using mass, air spaces, and insulation to reduce the various impact and airborne noises in a building.

When you add additional building requirements such as fire separations, mechanical and other systems, which can cause further difficulties in keeping the sound from migrating to adjacent units. These are a few examples of the technical details that must be addressed.

Architects will generally design a building using published reports based upon test reports on existing buildings. However there are also design issues that need to be looked at.

If the master bedroom of one unit is opposite the living room or kitchen of another unit, people trying to sleep will quite likely hear the stereo or noises from appliances. Therefore the building is generally designed so that like rooms are placed against each other. This is not always the case.

When purchasing a condo the expectation should be set accurately. Ask questions, shop around, and get to know what you can reasonably expect from a multi family dwelling, especially if you are used to living in a single family home.

Darrell Paul has dedicated his entire career within the residential building industry, is President of Qualistat Builders Ltd. (1986), current Director of Board of Governors with the Professional Home Builders Institute of Alberta (PHIBA), accomplished speaker/presenter in addition to instructing with SAIT.

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