Bespoke soundproofing solutions for Victorian mill conversion
A project by Clay Developments involved redeveloping the historic Old Town Mill in the Pennine hills close to Hebden Bridge, with the conversion work managed by its sister-company Clay Construction.
The mill’s original building was constructed around 1851 and was initially used as a cotton mill. In the 1880s, the complex was extended with the addition of a second larger mill building and associated facilities. Throughout its industrial life, the mill was used for various purposes ranging from the production of hosiery yarns and wool combing to sheepskin rug manufacture.
The plan developed by local architects Gagarin was to create a development of high specification homes overlooking the Calder Valley. After a successful phase one, the second phase involved converting the landmark mill building into ten properties, including triplex apartments.
This building, known as Carding Mill, was to retain its external character with its distinctive coursed square gritstone walls and Welsh blue slate roof. New high performance aluminium glazing and features such as perimeter walls created using natural reclaimed stone, would enhance these original features.
Internally, a more substantial transformation was required to remodel the building into two- and three-bedroom residential units which comply with the requirements of today’s Building Regulations, including acoustics.
The developer wanted to ensure the new homes created in Carding Mill were built to a standard that went beyond compliance with the minimum acoustic requirements in order to deliver a higher level of luxury for potential buyers.
Clay Construction approached Hush Acoustics to explore the design options and available materials to meet these aims. The technical team worked with the client to develop configurations for the separating floors, ceilings and walls which would comfortably meet the higher performance standards sought.
Hush developed an acoustic wall lining for the building’s dense concrete cavity block separating walls involving the Hush Enhanced Clip and Bar system, with the clips and the bars used at 400mm centres. The clips were screw-fixed to support the horizontal channels and an insulation layer of 25mm APR (acoustic partition roll) was then installed within the spaces between the bars to prevent the newly created cavity acting like an echo chamber and amplifying noise. A layer of 15mm acoustic plasterboard completed this wall lining.
As underfloor heating was being installed throughout the properties, acoustic issues had to be considered relating to the floor structure and build-up. A difference in floor levels also added complexity here.
Hush developed a UFH solution using an 8mm Hush FFR Underlay laid over the whole floor area – timber and screeded floors – onto which underfloor heating chipboard panels, complete with the pipes, would be laid. The UFH chipboard panels were then isolated at the perimeters using Hush RD Flanking Strip, providing a sub-floor for the floor finishes.
Hush also developed a design for the ceilings for further sound reduction. This involved fitting Hush Slab 100 sound absorbers in between timber joists and installing a Hush MF (metal frame) ceiling system across the ceiling area, suspended from the joists on acoustic hangers. Hush Slab 100 sound absorbers could then be used across the back of the MF ceiling grid and two layers of 15mm acoustic plasterboard were attached to the underside of the grid.
Soundproofing for the building’s structural beams which hold up the separating floors was also provided by Hush, along with solutions for any additional voids and minimising the acoustic impact of any services incorporated into the walls and floors.
The large structural beams were boxed-in with acoustically insulating boxing which was to stand independent of the beam. Hush Slab 100 was packed into the boxing to ensure the passage of sound is reduced through the beam and two layers of 15mm acoustic plasterboard created the outer skin of the boxing.
A sound insulation test was conducted when the properties reached an appropriate stage of completion and internal finishing. The results were particularly good compared to what would be expected on compliance level developments of a similar type.
Airborne sound tests revealed levels ranging between 52 and 61 dB DnT,w+Ctr, well above the compliance level of 43 dB. And for impact sound, two tests were carried out which registered levels of 35 and 37 dB L’nT,w, again surpassing the Approved Document E requirement of no higher than 64 dB.
Chris Bradford, Project Manager for Clay Construction commented:
“We had the pleasure of working with Hush Acoustics for the acoustic properties of the party walls and floors within each property. We did a lot of backwards and forwards with different options, mainly coming from myself trying to keep cost down, but we came to the agreement that soundproofing of each dwelling must be priority over cost and settled on a design.
I felt this had been the correct decision and it was confirmed when the sound test results came back, receiving amazing results. The results are more impressive due to the fact that we had only completed one side of the party wall. The incomplete side was still bare masonry. Now that the second property is in the final stages of completion we are now confident that the party wall surpasses the current legislative regulations to make the homes really comfortable to live in.
- Hush Slab 100
- Hush MF Ceiling System
- Hush Enhanced Clip and Bar System
- Hush FFR Underlay
- Hush RD Flanking Strip