Building Science, basement suite soundproofing
Hi all,
I wanted to talk about soundproofing and see what the community thinks about noise separation between units.
I am currently developing a legal basement suite in a single-family house in Edmonton Alberta, the house is in a B-C neighbourhood. After reading through the rules and regulations on what is required for fire and noise separation between the units in Edmonton, I found it a little weak. The code states that in Edmonton to have a legal basement suite I have to have 6 inches of bat insulation (or brown in insulation to capacity) in all the ceiling joists, except where there is HVAC running in the joist cavity in which case the main floor HVAC must be moved up to the top of the joist cavity with 3 inches of insulation placed below it and the downstairs HVAC must be moved to the bottom of the joist cavity with 3 inches placed above it. Resilient strips (a strip of metal that prevents thudding sounds from transfering) must be placed perpendicular to the joists and screwed to the joists. Finally half inch drywall must be screwed to the resilient strips and not touch the joists themselves. Above is the general requirements although if you read the rules themselves it’s slightly more nuanced than that. There are a couple other components, separate HVAC systems must be in place with no shared ductwork, to illuminate sound transfer between the units, also the smoke alarms must be tied together between the units.
After sifting through all the information and trying to imagine what it would be like to live in a to-code basement suite below the main floor, I think it would be a pretty loud place to live. I decided to go beyond code of the residential suites and aline more with the commercial apartment building code. For joist cavity insulation I placed 10 inches (Full depth of the joist) of acoustic rated installation, I will separate all of the HVAC and leave the spaces for the required insulation above and below, I am using the resilient strips as per the cities recommendations, and I am using a double layer of 5/8 fire code drywall.
There’s one more area that I decided to change which will help with sound and fire rating but mostly just make it a nicer place to live. I am removing the staircase in the building that goes up and down, I am instead cutting a 36 inch wide door in the foundation wall and pouring concrete steps on the outside of the building so the basement suite will have its own separate entrance. The separation Should help the soundproofing significantly by removing the last area for sound waves to travel through, it will also help the fire rating as there will be no easy path to travel between the units, and finally I imagine it will Make the basement suite a better place for someone to call their home.
My thought on doing all of this beyond code is first of all that I think I will be able to attract a higher quality of tenant who will be likely to stay longer and be more steady. The other benefit is that there aren’t many basement suites available that are quiet, bright (the door is mostly glass), and have their own entrance. I would like to know how other people approach the topic of noise between units and balancing the cost of construction with the quality of unit.
thanks!