A while back, a viral video went around poking fun at the infamous noisy upstairs neighbor. For some reason, I was tagged onto this video on social media by a bunch of my real estate friends, presumably because of its relevance to secondary suites.
If you haven't seen it, check it out at the bottom. It's pretty funny.
In reality, poor acoustics between housing units is no laughing matter, and can really stress people out. If you own a 2-unit house with tenants living there, that type of stress is going to find its way back to you that might sound something like this:
"Hey Bob, it's 2am. I'm sick of Dave upstairs practicing handball against the kitchen wall. Can you deal with it!?"
Sure, we can ask whomever to throw on a couple of industrial strength earplugs, but that's hardly a long term solution, and not likely to win you the coveted Landlord of the Year award.
So let's go over some solutions to help alleviate the noise that can travel between units, especially the floor system. The discussion will mostly be around the renovation that is done prior to separating the 2 units.
Understand that it's never 100%, but rather about mitigation.
Important Prior Considerations
Whenever you design a second unit, whether it's in the basement or upper unit, try your best to mirror the various rooms. Living room below living room; kitchen below kitchen; bedroom below bedroom, etc.
In addition to the ease of plumbing considerations, it's great to avoid situations where a night owl is up binge watching the new season of Walking Dead, while the person downstairs is trying to get to sleep. This is less likely to be an issue if bedrooms are matched up.
Plan your tenant profile or set expectations. Ideally you would have a nice professional quiet couple upstairs and a family with little kids downstairs, but that doesn't necessarily work from a market perspective since there's typically more bedrooms upstairs.
If there's young kids upstairs, let your lower unit tenants know that there's going to be noise, and it's something they will have to accept. When it comes to noise, it really comes down to a person's tolerance.
Sound Transmission Class (STC) Rating
After proper arrangement of spaces, choosing the right tenants, and setting expectations, the next best move is to build your separation to be as sound proof as possible. This is where STC (sound transmission class) rating comes in.
Building codes will require a certain sound proof standard, typically an STC rating of 50. To achieve this, you'd be looking at fire and sound insulation in the floor system, metal channels, and a 5/8" type X drywall. The drywall on the metal channels will absorb a lot of the noise.
If you had the ceiling height, additional options to make soundproofing even better include adding independent ceiling joists, and weaving a layer of acoustic quilt in between. An extra layer of drywall with seams staggered can also help. Even certain paints on the ceiling can improve things marginally.
In many cases, if you already have an existing assembly between the units that meet the fire separation requirements, the city may not enforce the sound rating, since that's really just a comfort issue. But depending on your own situation, you might be interested in upgrading it anyways.
In the Ontario Building Code, there's a reference document called the Supplementary Standard SB-3. In this document, there are hundreds of floor and wall assembly options that will specify a particular STC rating. It also shows the fire rating as well. This can come in handy when doing renovations to meet code requirements.(1)
Quick Fixes On Floor Surfaces
If the ceiling is already done, all is not lost. There are a few other supplementary solutions on the floor above that can help reduce the transfer of noise. Generally, thicker more "cushiony" flooring material is going to do better acoustically.(2)
Acoustic Underlayment and Mats - This is often laid on top of the subfloor before placing the flooring material. You can also lay this over top of existing old hardwood before new flooring such as carpet, laminate or engineered hardwood.
Floating Tongue-and-Groove Chipboard Floors - This can be laid on top of the acoustic underlayment and mats to provide additional sound proofing.
Burlap-backed Carpets - If you're into carpeting, burlap-backed type is much better for sound proofing than the less expensive foam-backed option.
Cushioned Vinyl/Fiber Flooring - These are good for high traffic areas (kitchens), are easy to install, look half decent, and relatively inexpensive. Great for rental properties.
Acoustic Sealant/Flanking Tape & Strips - Applying these to structural elements to isolate them is a good solution also.
Don't Be Vertically Challenged
Sound proofing a wall may also be important if there are any shared walls between units. For example, vertically split 2 unit homes, or split-level homes (back splits and side splits).
This can be done easily with acoustic insulation, and thicker drywall as well. Even within the unit itself, it may be worth investing a bit extra to reduce sound transmission between rooms.(3)
Just A Start
This was just a quick intro discussion around acoustic performance for 2-Unit homes. Sometimes these are code rules that are enforced, and sometime it's just good practice.
See notes below on where to get more info on sound improvement.
And worse case scenario, there's always the good old ear plugs!