~ What makes jack-up floating floors so effective? ~
In facilities like cinemas, music venues or gyms, vibration generated in one area can travel through the building’s structure and emerge as sound elsewhere. The best way to prevent noise travelling through a building is with a floating floor, and the best way to float a floor is with a jack-up system, says Tom Van Dongen, project engineer at Mason UK.
Imagine being on the edge of your seat at the cinema during a suspenseful moment of the latest blockbuster. Hearing the thud of weights being dropped in the gym upstairs, coupled with the bass from its sound system, would ruin the mood, wouldn’t it?
Floating floors interrupt the transmission of vibration through a building by introducing an air gap. A secondary concrete slab — usually 100-150mm thick — is installed on top of the existing one and supported by either rubber or spring mounts, with a gap in between. Much like the way a double-glazed window reduces the passage of heat, the floating floor reduces the passage of sound.
Mounting the floor
The simplest floating floors involve pouring concrete directly into a mould built on top of either rubber or spring isolation mounts, thereby creating the all-important air gap. The advantage of this method is that the floor is done once it’s poured, and no secondary work is necessary.
However, there are two critical things that need to be considered to ensure a floating floor works effectively. The first is choosing the right type of mount, which depends on the application. Rubber is best for reducing sound and high frequency vibration, while springs are better for low frequency and impact noise.
The second consideration is ensuring even load distribution across all the isolation mounts. For example, if a spring mount sits proud of the others when the load comes on, it will be under pressure before the others are even engaged. If a spring is over-compressed and becomes too dense, it will act as a bridge for vibration, negating the air gap. For rubber mounts, over-compression might lead to permanent creep, where the deflection in the element becomes permanent over time and the rubber can’t spring back in response to vibration.
Achieving even load distribution means adjusting each mount using shim and laser until they are all level, within one or two millimetres of each other. With four mounts per square meter of floor, the time this takes can add up quickly.
The jack-up system
Rather than using blocks or springs under a formwork layer to support the floating floor, the jack-up system uses a threaded mount to gradually lift the slab above the original floor. The more turns on the thread of the mount, the higher the floor rises. This creates the specified air gap and helps address the two considerations mentioned above.
Because the element is flat on the structural floor and you’re screwing down from above, the jack-up method means the load across each mount can be precisely calculated. Each turn of the thread produces a precise amount of compression on the element. This makes it much easier to ensure each mount carries the same load.
This also enables minute adjustments to the overall level of the floor. In my experience, a concrete floor is almost always more level after jacking it up compared to when we started, limiting deviations to +/- 5mm across the floor.
Another benefit is that after the floor is poured, but before it is jacked up, it can support heavier loads. On some sites, being able to continue moving heavy machinery across the floor while construction is completed makes a big difference.
Whether keeping a recording studio silent or keeping a weightlifting gym secret, the jack-up floating floor is the way to prevent the transfer of noise. To see videos of how floating floors are installed, or for more information about acoustic isolation in general, visit mason-uk.co.uk.
