If you are replacing the carpet in your Metro Vancouver condo with hardwood or vinyl, your strata council is going to ask about your floor’s sound rating. Two numbers come up, IIC and STC, and they are not interchangeable. Building your floor around the wrong one is the most common reason a strata application gets rejected. Here is what each rating means, which one your building enforces, and how to read a spec sheet with confidence.
Key takeaways
- STC measures airborne noise such as voices and television. IIC measures impact noise such as footsteps. Strata flooring rules exist for footsteps, so IIC is the number that counts.
- The BC Building Code only references IIC 55 for a bare floor. Your binding requirement is your strata bylaw, and many concrete towers ask for IIC 65 or higher.
- What matters is the finished assembly, the slab plus underlay plus floor, not the product spec sheet on its own.
- Bare hardwood rates about IIC 47, while the carpet you are removing rates IIC 75 to 85. The underlay closes that gap.
What STC measures, and why it barely matters here
Sound Transmission Class rates how well an assembly blocks airborne sound: a conversation, a barking dog, a television through the floor. It is useful for walls and ceilings, but it says nothing about the sound your strata actually worries about. A floor can have a strong STC number and still transmit every footstep to the unit below.
What IIC measures, and why your strata cares
Impact Insulation Class rates how well an assembly absorbs impact noise: footsteps, a dropped phone, a chair sliding back. This is the entire reason strata flooring bylaws exist. When a council reviews your application, IIC is the number it is checking, because impact noise is what generates complaints between stacked units.
The IIC 55 reference versus your strata bylaw
You will hear “you need IIC 72” repeated as if it were law. It is not. The BC Building Code recommends an impact rating and uses IIC 55 as a reference point for new construction, tested on a bare floor. For your existing condo, the document that binds you is your strata bylaw, and bylaws vary by building. Some older buildings accept IIC 65 to 68, while many newer concrete towers set the bar higher. Read your own bylaw before you trust any single number.
Product rating versus finished assembly
A spec sheet that shows a high IIC was tested as a complete lab assembly, usually on a concrete slab with a specific underlay. The floor product alone does not carry that rating. Your installed result depends on your slab, your underlay, and the install method together. This is why a quality acoustic underlay matters more than the brand name on the box.
How to hit your building’s number
Start with your bylaw, then choose a floor and underlay assembly rated at or above that target, with margin. Engineered hardwood and luxury vinyl both reach common condo thresholds with a good cork or rubber underlay. Tile usually needs a dedicated sound and decoupling membrane. Keep the spec sheets, because your council will want to see the IIC and STC numbers in writing.
The numbers that actually matter
Concrete figures make this real. Bare hardwood installed directly on a concrete slab tests at an impact rating of roughly IIC 47, which is low enough to telegraph every footstep to the unit below. Carpet over a good underlay sits far higher, around IIC 75 to 85, which is why so many older buildings simply wrote “carpet” into their bylaws. A hard-surface floor only gets close to acceptable when a proper acoustic underlay is built into the assembly.
The key word is assembly. The rating belongs to the whole floor-ceiling system, slab, underlay, flooring, and the ceiling below, not to the plank you pick off a sample board. A vinyl or engineered floor with a quality acoustic underlay can land in a very different place than the same plank over cheap foam. That is why a spec sheet number alone never tells the full story.
Why STC is the wrong number for your floor
STC, the Sound Transmission Class, measures airborne sound: voices, music, a television passing through a wall or floor. IIC, the Impact Insulation Class, measures impact sound: footsteps, dropped objects, a chair sliding. The complaint that gets owners hauled in front of a strata council is almost always impact noise from the unit above, which is an IIC problem, not an STC one.
This trips people up because a product can advertise a strong STC and still perform poorly on impact. When your council asks what your floor is rated, they mean IIC, and they mean the assembly’s rating, ideally confirmed by a field test. Quoting an STC number, or a lab IIC for a different assembly than yours, is how approvals stall.
Lab rating versus the field test
There are two versions of the number. The lab IIC comes from an ideal test chamber; the field rating, sometimes written FIIC, comes from testing the actual installed floor in the actual building, and it is usually a few points lower. Some buildings accept manufacturer assembly data, while others require a field test after installation to confirm compliance. Knowing which your building wants before you start saves an expensive surprise at the end.
How Canadian Home Style helps
We supply and install condo floors across Metro Vancouver every week, so we match the product and underlay to your building’s rating and hand you the documentation your strata requires. From our North Vancouver showroom you get one local team that takes a floor from selection through a clean, compliant installation.
Book a showroom consultation or request an in-home consultation, and our team will help you choose a strata-ready floor and prepare the spec sheets your council needs.
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Frequently asked questions
Is a higher STC the same as quieter footsteps?
No. STC measures airborne sound, not impact. For footstep noise you need a high IIC. Look for the IIC figure on the assembly spec sheet.
Does the floor product’s IIC rating apply once installed?
Only if your slab and underlay match the tested assembly. The rating belongs to the full assembly, so build yours to the spec the rating was based on.
What IIC should I aim for?
Match or exceed your strata bylaw. Where the bylaw is silent, aiming for IIC 60 or higher on the assembly is a safe, council-friendly target in most Metro Vancouver buildings.
Is a higher IIC number better?
Yes. A higher IIC means more impact sound is blocked. Bare hardwood on concrete is around 47; carpet with underlay reaches 75 to 85.
Does my floor’s STC rating help with strata approval?
Rarely. Councils are concerned with impact noise from above, which is measured by IIC, not the airborne STC rating.
Will my building field-test the floor?
Some accept manufacturer assembly ratings; others require a field IIC test of the installed floor. Confirm which before you choose your assembly.