Sound & Fury After Creaks & Groans
Jim Coulson on noisy floors
LAST month I wrote in CFJ about the annoying creaks and groans that can emanate from floors – especially those laid with T&G chipboard.
Here I want to elaborate on the whole issue of sound passing through floors – in party floor constructions, such as are found between flats and apartments.
Noise coming from your neighbours above (or sometimes below) can be really irritating: and there are numerous properties which have been converted in the past, from former single-occupancy houses, into separate dwellings. And these have not always been done very successfully, from a sound-deadening point of view.
The biggest issue, of course, is the transmission of sound. But it is not always understood that this can happen in two distinct ways: airborne sound and impact sound.
Airborne sound is where noise generated within a room (such as loud music) can be heard in the other property – above or below – simply because of its great volume.
And this can be reduced (if not fully eliminated) by means of some form of layer between the floor of one flat and the ceiling of the one below, for example: and this layer may be either very dense, or it may be very lightweight and act as an insulation.
In the past, it was assumed that density was the answer: and so a layer of sand (called ‘pugging’) was introduced – which greatly increased the weight on the floor joists, and so was not always practicable. In historical times, even crushed oyster shells were used: as by Sir Christopher Wren, in his modifications to Hampton Court!
But nowadays, it has been realised that a mineral quilt insulation, or similar, can effectively absorb airborne sound to a great extent. But that leaves us with impact sound.
That is where you can hear the footfalls, for example, of those dancing to the loud music, drumming on the floor above; and thus are carried through and then reverberate from the ceiling (effectively, using the ceiling like a drum-skin, or diaphragm, to transmit the impact sound).
The only answer here is separation – where the floor and ceiling are not joined together!
This is difficult to do without careful detailing: but it can be achieved, by means of a ‘floating’ floor which sits on top of the original floor surface and is, in effect, a ‘raft’ that is not connected physically to the ceiling below.
In this case, the insulation which acts as the airborne sound-deadening layer, is also doubling as the ‘floating’ mechanism, which carries the room’s internal floor surface above the original (structural) floor – so that no direct contact is made between them.
And in such cases, it is usual for the insulation to be rigid, or semi-rigid: so that it does not get squashed over time, and thus lose its other sound-insulating qualities.
Fitting a good, sound-proofing floor is not easy. But it is very easy to get it wrong by somehow fixing parts of the floor together, when they should be kept separate. For example, by nailing through the ‘floating’ layer and accidentally fixing it directly to the structural floor beneath. Sound advice you might say? CFJ
Jim Coulson FIWSc FFB is director of TFT Woodexperts, based in Ripon, North Yorkshire
T: 01765 601010
This article has been reproduced from the Contract Flooring Journal website. You can find them at www.contractflooringjournal.co.uk.