The renovation is complete, yet every word of a telephone conversation can be heard from the neighbouring room. The sound of the television in the evening is even more noticeable: it’s hard to make out the words, but the bass carries through the wall almost perfectly. Most often, the reason is that the partition is too flimsy: a frame with a single layer of plasterboard and a hollow space inside.
Heavy-duty partition walls are made from thin concrete blocks, which are manufactured specifically for internal walls. They differ from standard wall blocks primarily in their width. Among the concrete blocks on the page https://shop.kovalska.com/concrete-blocks/ Partition blocks are 80 and 90 mm thick, whilst wall blocks are 190 mm thick. Thinner blocks are usually used for walls between rooms: wall blocks are heavier and quieter, but take up twice as much space.
What affects the vocals, and what affects the bass
Sound causes the wall to vibrate, and the wall transmits these vibrations to the air on the other side. The heavier the wall, the harder it is to make it vibrate. In physics, this is known as the law of mass: in theory, every doubling of mass adds around 6 dB of sound insulation; in practice, it is slightly less.
The frame works differently: the cladding, the insulation and the air gap between them dampen vibrations. If the frame is tightly packed with insulation, clad in two layers, and the cladding on both sides is not rigidly joined by a shared profile, it copes well with voices. The weak point of lightweight structures is low frequencies: bass from a speaker or the hum of a washing machine often passes through them more easily than through heavy brickwork.
If a lightweight partition is already in place, the sound insulation can be improved without dismantling it: an additional layer of plasterboard mounted on a separate frame and filled with insulation acts as a second, independent wall. The result depends on the number of cladding layers, how the studs are fixed, and how well the joints are sealed.
Where sound seeps through the wall
Even a solid partition loses most of its effectiveness if the sound finds a way round it. Most often, it passes through:
- a gap under the door and a lightweight, hollow door leaf without a seal;
- sockets fitted on both sides of the wall, exactly opposite one another;
- an unfilled gap between the partition and the ceiling;
- masonry without plaster, where sound travels through the pores of the blocks and the empty vertical joints;
- a ventilation grille above the door or a shared ventilation duct, which carry sound just as well as a gap.
Therefore, the concrete partition is plastered on both sides, and the sockets are spaced at least a few tens of centimetres apart. Without this, even replacing the studwork with brickwork may not make a noticeable difference.
When is brickwork justified, and when is a framework sufficient?
Partition walls are justified where low-frequency noise is a problem: between the bedroom and the living room with the television, near the laundry room or boiler room, and between the bathroom and the bedroom, where the sound of water in the pipes can be heard at night. The difference in thickness is less than it seems: a 90 mm block with plaster on both sides takes up 12–13 cm, whilst a frame with double cladding takes up around 10 cm.
There is another limitation to brickwork: weight. Before erecting a heavy partition, checks are carried out to ensure that the floor slab can support it, particularly if it is made of timber. The masonry is not built right up to the ceiling: a gap is left at the top and filled with a flexible material to prevent the wall from cracking if the floor sags slightly. For a walk-in wardrobe, a storeroom or to divide up the space, a timber frame is perfectly adequate, and it is several times lighter than brickwork.
