Footstep and Impact Noise in Multi-Family Dwellings

25 Sep Footstep and Impact Noise in Multi-Family Dwellings

Noise issues are common in apartments, condominiums and other BKL Consultants Ltd Footstep Impact Noise Problemmulti-family dwellings, and footstep/impact noise is currently the most significant. Footstep / impact noise isolation is only loosely related to the airborne noise isolation (isolation of noise which is generated in the air such as from loud speakers or from voices and is typically governed by Building Code requirements in most jurisdictions). Consequently, a floor system can have an excellent airborne isolation that meets building code standards, but can still have a footstep/impact noise isolation deficiency. Although the noise isolation properties of the construction details found in multi-family buildings are substantially superior to those found in single family dwellings, the proximity of the occupants when compared to the physical separation offered by single family dwellings leads to residents being more aware of the activities of their neighbours. Unfortunately, the noise isolation expectations of the residents, many of whom have moved from single family dwellings, often exceed the capabilities of the construction.

 

…the noise isolation expectations of the residents, many of whom have moved from single family dwellings, often exceed the capabilities of the construction.

 

Footstep or impact noise is observed both in buildings of concrete construction and wood frame construction. However, there is a clear difference in the nature and extent of the problem in these two constructions. In both cases, if the floor finish is “hard”, i.e., tile, hardwood, or the like, footstep impacts will clearly be transmitted to any spaces below. However, with a structural concrete floor such as that found in highrises, if the floor is covered with a quality carpet and underlay, footstep impacts are generally attenuated adequately for most occupants. On the other hand, in wood frame construction, the floor system is less massive and stiff than that found in concrete construction. Thus, the impact from the footstep tends to cause the floor to deflect and produces a low frequency “thump”, even when quality carpet and underlay is used.

 

It has been our experience that floor covering disputes have been a source of major expense and aggravation to both owners and Strata Corporations, incurred both as legal fees and as consultant fees.

 

Footstep/impact noise is generated by the striking of a hard object (the shoe, the dragged chair, the dropped book, etc) on a hard surface. The harder the surface or object, the more noise that is generated, and conversely, the softer the surface or object, the less noise generated. This is why a person in bare, or stocking, feet generally will cause less noise than one in boots. This is also why a carpet performs substantially better than a harder surface such as vinyl tile, hardwood or ceramic tile. In terms of loudness, footsteps would be 4 to 8 times louder with a hardwood floor than with a carpeted floor for similar constructions. Even with hard floors rafted on resilient supports, the impact noise transmitted through to a lower suite will be substantially higher than for a standard floor with carpet and underpad, likely still in the range of 4 times as loud. Removal of the existing carpet and underpad and replacement with a harder flooring will inevitably lead to substantial increases of footfall and other impact noise in the suite below.

BKL Consultants Ltd floor underlay impact noise

Several manufacturers have developed underlayment systems in an attempt to improve the isolation of floor systems with hard floor toppings. Unfortunately, while most of the systems offer a modest improvement in the measurable impact noise isolation, none of them to date offer sufficient improvement to be judged by the occupants as being successful. Impact noise isolation has been quantified by an ASTM test procedure for measuring Impact Insulation Class (IIC). This is a weighted decibel measurement where an increase in IIC rating of 10 decibels can be approximately related to a halving in subjective loudness. It has been our experience that IIC ratings of over 70 are generally required for most occupants below to find the impact noise isolation acceptable. Typically, the following IIC ratings can be expected for standard floor conditions.

BKL Consultants Ltd IIC impact insulation class testing

Floor Condition
Expected Range in IIC rating
Bare concrete floor; concrete floor with ceramic tile set with thinset mortar; concrete floor with terrazzo finish
25-30
Concrete floor with linoleum or vinyl flooring
40-45
Bare wood frame floor with 1½” concrete floor topping and ceramic tile finish
35-45
Wood frame floor with 1½” concrete floor topping and nailed hardwood, linoleum or vinyl flooring
40-50
Concrete floor with floated hardwood flooring
45-50
Wood frame floor with 1½” concrete floor topping and floated hardwood flooring
50-55
Concrete floor with proprietary floor underlayment and finished flooring (tile, hardwood, etc.)
50-60
Wood frame floor with proprietary floor underlayment under 1½” concrete floor topping and finished flooring (tile, hardwood, etc.)
50-60
Any of the above floor systems with carpet or area rug, (but without underlay)
60-70
Any of the above subfloor systems with quality carpet or area rug and underlay
70-80

 

From our experience, IIC ratings of less than 60 are often rated as Unacceptable. IIC 60-70 are often rated as Marginal and IIC greater than 70 are required to ensure that the floor system will be rated as Acceptable.

 

Should we be engaged to work on a project involving flooring and acoustics, it would be our recommendation to select a floor system that would fall within the “acceptable” range. However, we recognize that almost all installations in multi-family dwellings are hard floor surfaces. This would lead to the conclusion that occupants may be becoming more tolerant and accepting of footfall noise impacts. Thus there is a demand for knowing how to specify the best installation conditions to control these impacts when a hard flooring surface is used.

Stipulating the limitations mentioned above, if a hard floor topping is going to be employed, it is recommended that the following be considered:

 

  • First, whatever topping is used, it should be isolated from the subflooring using an isolating element that has been tested using similar structural floor construction (i.e. wood frame test for wood frame buildings, and poured concrete test for concrete high rises) and found to demonstrate (with independent lab test results) an ability to achieve an IIC rating of 58+
  • Second, there can be no bridging of this isolating element with fasteners of any type
  • Third, if a fracture mat is required, it should be installed in addition to the isolating element, unless independent lab test results demonstrate that the fracture mat is capable to achieve an IIC rating of 58+ by itself

 

Occupants of dwelling units with hard floor toppings (hardwood, vinyl, ceramic tile, etc.) must recognize that the floor impacts resulting from their activities are more readily transmitted to units below and must take active steps to limit the production of these impacts. Actions which will all help to reduce impact noise transmission to the lower unit include the removal of hard soled shoes or boots in favour of slippers or stocking feet, control of heavy impacts resulting from rapid movement through the unit or from dragged or dropped furniture, and placement of area rugs or carpets.

It has been our experience that floor covering disputes have been a source of major expense and aggravation to both owners and Strata Corporations, incurred both as legal fees and as consultant fees. These charges can rapidly run into the tens of thousands of dollars. Accordingly, it is proposed that Strata Councils, concerned about noise impact issues, consider adoption of the following by-laws:

Possible Strata By-law Amendments

“1. Floor coverings in the interior of any strata lot shall not be replaced with less resilient coverings than the pre-existing coverings without the prior written consent of the Strata Council. For the purpose of this clause ceramic tile, marble or the like shall be considered less resilient than vinyl tile, hardwood flooring or the like which shall be considered less resilient than carpeting, carpeting & underpad, or the like.

2a. Where hard floor coverings are permitted, and where they are located in a Strata lot that is above another strata lot, the floor coverings must be installed using a resilient underlay which has a laboratory tested rating of Impact Insulation Class (IIC) of 58 or higher when tested on a similar floor structure.

2b. The floor covering must ‘float’ on the isolated underlay with no fasteners or other bridging through to the structure. ”

We recommend that Strata Councils seek legal advice on the appropriate wording for the above by-laws to suit their specific circumstances.

Whether or not a floor covering by-law has been approved by a Strata, owners should be aware that any action that they take which results in excess noise impact on their neighbours, likely contravenes Strata by-laws regarding “quiet enjoyment” of their unit. This could lead to fines and legal consequences. Therefore, we would caution an owner to consider the consequences before making a decision on floor covering changes in any suite renovations.

Note: The information contained in the above article is provided in good faith based on BKL’s experience. However, we accept no liability for any damages resulting from the application or mis-application of this advice.

14 Comments
  • insurance
    Posted at 09:25h, 27 September Reply

    I’m not positive the place you are getting your info, however great topic. I needs to spend some time studying more or understanding more. Thanks for magnificent info I was in search of this information for my mission.

    • bkladmin
      Posted at 17:44h, 01 October Reply

      Thank you, It’s based on a few decades of our own experience! 🙂

  • red sole shoes
    Posted at 10:11h, 30 September Reply

    I love the way you wrote this article. This is wonderful. I do hope you intend to write more of these types of articles. Thank you for this interesting content!

  • Brittney
    Posted at 15:36h, 02 October Reply

    Very interesting article. However, the focus places the responsibility of sound dampening on the people “making the noise”. What options are available to the people who have to “live with the noise”. Are there materials we can put on our ceilings or walls to reduce the amount of incoming noise from our neighbors?

    • bkladmin
      Posted at 17:47h, 06 October Reply

      Unfortunately, there is not much that noise receivers can do that wouldn’t cost an arm and a leg… Good idea though – we should add another section to this write-up.

  • Bruce
    Posted at 09:52h, 24 April Reply

    Just wondering if you have available the “another section” you mention above in October, 2012 response, to assist those who live in the lower living space. There appears to be some online suggestions for example
    about adding acoustical tiles to current ceilings etc. to assist in footfalls and so forth. Your perspective would be greatly appreciated!

  • Hearing Noises
    Posted at 09:47h, 29 May Reply

    Fantastic article. This response is slightly off and on topic. We also hear the flanking noise generated from our neighboring unit (Townhouse complex). We can hear them walking on the hardwood flooring and using stairs. This is the least of our problems.

    The off topic portion of my reply, is that our party wall isn’t well isolated, we heard cupboards, microwave closing, closet doors and shower door closing. All these noises causes a “thumping” sound in our unit. Also can hear coughing and some conversations (some of the sounds are “muffled” but clearly someone conversing or singing in the bedroom).. Driving us crazy.

    Does BKL offer any residential services to help block out some of these noises on the common wall?

    Thanks so much for any input.

  • neil spiegel
    Posted at 11:16h, 23 June Reply

    Does the ceiling assembly below help to ameliorate for IIC as well. That is, if you use an assembly as described above in the 50 to 60 range (ie underlay and gypcrete) if done in addition to a rsic and quietrock ceiling with Roxul help to improve the acceptability of foot fall noise or is the solution largely independent.

    Thx

  • bkladmin
    Posted at 17:59h, 24 June Reply

    Constructing a good independent ceiling, for example, two layers of 5/8″ Type X gypsum wallboard, with insulated airspace (typically fibreglass or rockwool batts), minimum 4″ deep, sealed with acoustic (non-setting) caulking around the perimeter, will make a significant improvement. However, budget or space constraints usually means this option is abandoned.

    We had feedback from one client that found the only practical approach was to pay for a custom carpet with thick underlay for their upstairs neighbour. It was wall-to-wall but bound around all the edges like an area rug and cost them around $2,500. They said it resolved their issue by “about 85 or 90 percent” and was money “very well spent”.

  • Henrianne Slattery
    Posted at 15:53h, 02 April Reply

    We are researching solutions for our hard surface impact sound issues. What works BEST over concrete floors, using laminates. We have several hundred apartments in this retirement home. Buyers are choosing laminates and driving their downstairs neighbors nuts. Each apartment is different but problem is the same.
    Your writings on the subject are useful but we need specifics. Is hiring an acoustic engineer the answer?
    Thank you for your response.
    yan

  • Kevin Mason
    Posted at 08:05h, 10 June Reply

    We are replacing our old carpet with porcelain “timber look” tiles throughout our apartment & have a unit below and would like to make sure we comply with using an acoustic underlay, but already have 12mm thick timber parquetry floor sitting on a 6mm cork/magnesite insulation over a concrete slab.

    We have researched the Davco & Regupol BCA approved acoustic products which we are wanting to place on top of the existing parquetry then apply a thick approx. 20mm screed concrete bed with the tiles over the top of this or do you suggest taking up the parquetry & placing down the acoustic matting on the slab? Assume the existing parquetry on the magnesite/cork will also provide some acoustic dampening?

    Do you have any suggestions or comments that can assist & have you suggested these products before or do you suggest other products?

    Kind Regards,

    Kevin Mason
    0419645862

  • bkladmin
    Posted at 09:55h, 06 August Reply

    The details often become critical to understanding a specific scenario. Please contact us directly with any project specific questions using our contact form at http://www.bkl.ca/contact-us/

  • Darcy Lindahl
    Posted at 09:03h, 05 March Reply

    Hi I’m living in a strata underneath noisy laminate flooring which the manufacture claimed in their sales literature had an IIC rating of 71. Our strata council believed it and allowed the installation despite me having provided them with an older pdf version of this article pointing out the real world rating would be in the 50 to 60 range at best.

    Thanks for pointing out that the ratings need to be backed up by independent lab test results. This is supported by The City Of Vancouver Noise Control Manual at page 24 stating strata councils should consult with a noise control professional, not a hardwood flooring or resilient underlay salesperson.

    Your article states IIC ratings of less than 60 are often rated as unacceptable, and that It has been your experience that ratings of over 70 are generally required for most occupants below to find the impact noise isolation acceptable., Why then does the possible bylaw amendment you include state 58 as a base line? Shouldn’t you be recommending something in the acceptable range (or at least in the marginal range) rather than in the unacceptable range?

    • Mark Bliss
      Posted at 20:47h, 19 October Reply

      Thanks for your comments Darcy. With the perception of sound being so subjective, choosing a minimum acceptable level basically comes down to statistics as there will always be a percentage of the population that would still rate it unacceptable. IIC 58 is a potentially acceptable compromise between an owner`s desire for hard flooring and the impacted occupants` desire for quiet.

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