As a manufacturer of light gauge steel-framed (LGSF) buildings I feel obliged to comment on the problems that have arisen after completion of the Kirby Court contract at Greenwich Millennium Village (6 May, pages 26-29).
We are completing about 20 apartments per week and have not had a sound problem. LGSF works extremely well but laboratory tests are very limited when considering flanking of sound. The matrix of party walls and floors above, adjoining and below requires careful consideration.
It is very difficult, if not impossible, to achieve top quality when an LGSF structure is “stick built” on site. Trusses, such as those used at Kirby Court, should never be site assembled.
Some people in the LGSF industry think that any drylining or ceiling fixer can adapt to this technology overnight. This is not our experience. Site personnel must have a high level of training to fully understand the implications of not complying with the specification. We also believe the manufacturer must take responsibility for the contract from design to handover.
One reason for the creaking floors could be the omission of the resilient bars on the underside of the structure. Although their primary purpose is to enhance the acoustic properties, they also act as “bridging” in conjunction with the oriented strand board. The bottom element of the truss must also be fixed securely to a wall, preventing truss rotation. Were the floors designed to L/240 or L/360?
Pictures of the truss show the elements connected with what seems to be a single screw. One screw per connection seems inadequate and it is possible that some slip is occurring at connection locations, which is probably causing the floors to deflect beyond design levels and consequently causing creaking.
To eliminate all these risks, the manufacturer should specify a simple metal deck and concrete floor supported on LGSF walls. Potential buyers always feel more comfortable on a concrete floor.
Eoin Madden, managing director, Stanta