Building Envelope Case Study: West Huskisson Docks

Situated near the mouth of the celebrated and evocative River Mersey, Liverpool’s historic Huskisson Dock dates back to 1852. Originally dealing with timber, it gradually developed as a grain trading centre and also provided berthing facilities for passenger ships on North American routes.

After being destroyed During World War Two, Huskisson Dock underwent extensive rebuilding after the war. In 1960 a quarter of a mile long grain store was constructed, running along almost the entire length of the dock.

However, over the years, the building had fallen into a state of disrepair.  Owners Peel Ports decided to give it a new lease of life with complete refurbishment of the external building envelope.

Refurbishment specialists Lester Fabrication and Cladding were appointed to carry out the work, who recommended metal roof and wall cladding profiles by Panels and Profiles, in Colorcoat HPS200 Ultra®.

Made in the UK to ISO 14001, for a lower carbon foot print, Colorcoat HPS200Ultra® is the most durable pre-finished steel on the market. It incorporates advanced coating technology, providing superior corrosion resistance, especially in challenging environments, with twice the colour and gloss retention of standard
plastisol products.

Project managers at Peel Ports agreed with the assessment and recommendations of Steve Lester and his colleagues and ordered a total of 24,000m2 of  metal cladding profile in Colorcoat HPS200 Ultra®, consisting of the 0.9mm thick  R32 profile on the roof and the 0.7mm thick C32 profile on the
walls.

Colour choice was Merlin Grey for roof and walls. A contrasting Black finish was chosen for associated trims and flashings and above service doors. Steve Lester and his team began to prepare the building for its new envelope by removing the existing profiled aluminium roof sheeting and cleaning the old purlins before they could accommodate the R32 profile.

“We then broke down the concrete between support columns on the lower half of the walls. This enabled us to incorporate rooflights to improve internal daylighting levels.”

“We fixed miles and miles of new cladding rails to the structure to accept the new walls in the C32 profile.”
Reflecting on the completed project, Steve Lester observed: “The roof and wall profiles look superb. The building is unrecognisable compared to what it looked like before refurbishment.”

A Sound Approach to Achieving the Best of Both Worlds

In building envelope designs calling for high levels of acoustic performance, there is often a potential trade-off between the conflicting requirements for controlling sound reduction and sound absorption. Sound reduction refers to the control of either internal or external noise in a building.

Typical applications include concert venues, where one is trying to avoid excessive noise levels from breaking out and buildings in areas near noisy facilities, such as airports, where one strives to achieve precisely the opposite. Sound absorption is the more common acoustic feature required by designers.

It is the control of attenuation, or internal reverberation of sound against building surfaces. A school sports hall is a very typical, everyday application requiring attention. Although most projects usually require one method of acoustic control, some still need to address sound reduction and absorption in the same envelope construction.

A typical example would be a concert venue situated close to or underneath a flight path of a major airport and with nearby residential properties. Decks are typically perforated to break up sound waves and assist absorption. However the perforated open area also allows sound to escape into the roof cavity, thus lowering reduction values.

There may also be requirements of a project where longer spans are required and  perforated deck  is unsuitable.

How, then, can these conflicting requirements be achieved at a minimal cost?

The answer is to install a plain deck with a  perforated under lining sheet, as indicated:-

Click to enlarge

Installation of a D159 plain roof deck provides maximum spanning capability, whilst the addition of RL32/1000 perforated liner enhances absorption values with a 22% open area, and provides a more aesthetically pleasing finish. Sound is absorbed into the trough infill fillets, as for a perforated deck profile. This liner may be installed directly below the deck, or positioned under the beams to hide all support structure.

Comparison of ex works prices, based on 1000m2, indicate that there is no additional cost increase, for profiled elements, by offering an underlining system.

There would be costs for supporting zed spacers, additional fasteners and installation time. However the combined benefits of enhanced acoustic absorption, reduction and aesthetics will more than justify the modest additional expense.

Diaphragm design and construction in Green Roofs

In our previous green roof focus, we noted that the growing popularity of a hitherto “alternative” solution has not been at the expense of the advantages of more established options.

Green roofs are heavy in comparison to almost every other roofing method. However, if they are used in conjunction with structural decks and trays, they can still provide engineers and building owners with the economies and aesthetic enhancements that can be gained from diaphragm, or stressed skin, construction.

Diaphragm action essentially concerns the judicious selection of a structural deck or tray and designing the roof layout such that horizontal wind load forces are transferred into the deck and the structure.

This complex technique, usually accomplished with the use of the Corus Roof Decking Software package, can replace cross bracing and reduce secondary steelwork.

Not only does this method save money, it also provides a cleaner internal building appearance that is commonly considered to be better looking than standard techniques.

As if all this were not enough justification, there are also no real additional costs associated with the diaphragm/stressed skin method, save for the use of relatively low-cost primary fasteners around the building perimeter.

So with all these very attractive benefits to be gained, why on earth doesn’t every project go down this route? Well, as always, the term “horses for courses” applies.

Straightforward, square buildings are the easiest to design in this way. It gets more problematic, however, when rectangular , long, thin structures are necessary, for reasons of location and/or function. It is also essential to have at least three braced walls.

Other essential roof requirements, such as rooflights and other roof penetrations, can also quickly count against the viability of the diaphragm option. Stressed skin construction only allows for 3% of the total roof area to be “open”. If we take the example of a building that requires considerable natural roof lighting, this factor alone is going to eliminate the option.

Armed with your drawings showing your proposed deck layout and braced walls and line loads at diaphragm edges, our technical support team is able to quickly advise you as to exactly what is possible on your own project, via email or by telephone on 0845 30 88 330

Green Roofs – Acoustic Considerations

As green roofs become an increasingly popular solution, their image as an “alternative” method of construction has not completely disappeared. One might therefore consider that caveats lie in wait and that they do not offer all the common benefits of more established options.

In practice, however, nothing could be further from the truth.

And nowhere is this more apparent than in the area of acoustics where green roofs, supported by Corus decks, offer a completely comprehensive solution, with additional advantages of their own thrown in for good measure.

Although acoustics has moved more into the mainstream of desirable building features in recent years, it is still something of a “grey art”. We often talk to designers who are confused between the sometimes conflicting requirements of sound reduction and sound absorption.

Sound reduction refers to the control of either internal or external noise in a building. Typical applications include concert venues, where one is trying to avoid excessive noise levels from breaking out and buildings in areas near noisy facilities, such as airports, where one strives to achieve precisely the opposite.

Sound absorption is the more common acoustic feature required by designers. It is the control of attenuation, or internal reverberation of sound against building surfaces. A school sports hall is a very typical, everyday application requiring attention.

Green Roofs installed over Corus decks and trays can be fine-tuned to achieve sound reduction and/or sound absorption. They actually offer two significant advantages over other types of roof construction: -

• Green roofs contain soil and sedum which gives them good mass. This is of critical importance in a situation where sound reduction is required, as they provide a natural sound barrier that can be further tuned by careful attention to detail with the underlying construction.
• Reduction of the drumming noise created by rainfall on the external roof surface is an important acoustic consideration in many buildings. Green roofs offer a naturally soft outer surface that provides a “built-in” solution to an age old problem.

Choice of deck or tray plays an instrumental role in the success of a properly executed green acoustic roof project.

We offer a full range of perforated decks and trays, for applications requiring sound absorption. The perforations help to break up sound as it hits the underside of the roof construction, thereby reducing reflectivity.

Dense mineral fibre is the general insulant of choice for acoustic applications. It is therefore common for a tissue or foil layer, to prevent fibres from falling through the perforations, to be inserted in the pans of decks or trays, or directly above the deck.

The “open area” – the degree of perforation of the deck surface – is critical to the success of sound absorption. We can provide decks and trays with open areas between 5% and 30%. In an ideal world, everyone would specify the 30% maximum. However, as the open area increases, so the structural performance of the deck or tray in question reduces. This has implications for the amount of bracing and secondary steel that will be required. Therefore compromises often have to be made, either in favour of better sound absorption levels and the consequent increase in steelwork, or vice versa. Cost is clearly a key driver here.

Moreover, if a project requires both sound absorption and reduction, the bigger the open area, the more sound breaks into the roof construction, increasing noise break in and/or break out levels.

As mentioned earlier, the superior mass of the green roof construction helps to reduce the deployment of other sound reduction “counter measures”.

Bespoke mineral fibre acoustic infills that fit flush into the deck/tray pan profile are the most beneficial option, because they act as a direct barrier to sound entering the construction.

Flexible, high density polymer mass layers with exceptional sound reduction properties are also commonly used in conjunction with insulation, particularly when very high levels of control are required, especially where very low frequencies need attenuation.

We hope that this blog entry has given you some general food for thought when considering acoustic performance in green roofs. Please contact our technical support team if you require any specific advice on 0845 30 88 330.

Green Roofs – Choosing the right metal deck and tray

With a focus on the use of structural decks and trays on green roofs, we highlight some of the main design considerations and deck attributes to look out for during the product selection process:  -

• Decking systems in England & Wales must be designed and installed to meet the Building Regulations 2000 and Approved Document L2A 2010 (Scotland to be designed and installed to meet the Scottish Building Regulations 2007).
• Where used as a vapour control layer, the metal deck must be reasonably airtight so that the air permeability does not exceed 5m³/h/m² at an applied pressure of 50pa in accordance with the Building Regulations 2000, Approved Document L2A 2010.
• Deck profiles must achieve minimum Class C non-fragile assembly when tested to ACR(M) 001:2005 Test for Fragility of Roofing Assemblies.
• Fixing fasteners can be either carbon steel or austenitic stainless steel (Stainless steel fasteners required for aluminum deck and for fixing into timber supports)
• Fire rating of roofs is not generally applicable. However, for surface spread of flame, decks will achieve Class O to the Building Regulations, Class 1 to BS476: Part 7. Metal deck profiles are non combustible to BS 476 Part 4.
• Corus (Tata Steel) produce a range of nine trapezoidal decks from 35 mm deep to 210 mm deep, and three structural trays from 90 mm deep to 145 mm deep, in steel or aluminum, in various gauges and finishes.
• Decks and trays may be perforated to enhance acoustic absorption, assisting with reduction of reverberation time, thus minimizing the echoy effect within the room environment.
• Decks provide lateral restraint to support structure, or may provide full diaphragm, or stressed skin, design, which will minimize bracing structure.
• Decks must be designed to support all relevant loads, designed to British Standards or Eurocodes:-

British Standards:

(a) Dead loads: Calculate to BS 6399-1

(b) Imposed loads: Calculate to BS 6399-3

(c) Snow loads

(d) Diaphragm Loads: BS5950 Part 9

(e) Wind loads: Calculate to BS 6399-2

(f) Basic wind speed (Vb):

(g) Altitude factor (Sa):

(h) Direction factor (Sd):

(i) Seasonal factor (Ss):

(j) Probability factor (Sp):

(k) Terrain and building factor (Sb):

(l) Size effect factor (Ca):

(m) External pressure coefficients (Cpe):

(n) Internal pressure coefficients (Cpi):

(o) Dominant opening:

Eurocodes:

BS EN 1991 Eurocode 1: Basis of Design and Actions on Structures

Part 1     Basis of design

Part 2-1  Densities, self weight and imposed loads

Part 2-2  Actions on structures exposed to fire

Part 2-3  Snow loads

Part 2-4  Wind loads

BS EN 1993 Eurocode 3: Design of steel structures

Part 1-3 Cold formed thin gauge members and sheeting

If you require any guidance on any aspect of structural roof deck and trays, such as choosing the right deck for the right application, or simply require more advice on any of the above points, please contact the technical team on 0845 30 88 330

Sustainable application of metal decking

As a 100% recyclable product, metal roof decking is the ideal choice when sustainability in construction is a key consideration. However, there are a number of other benefits to using metal decking in the construction of single-ply, standing seam or green roofs.

It’s incredibly strong for its weight, the fact that metal decking can span up to 12 metres allows building designers to lose much of the secondary structure.  Roof deck is fast to lay therefore reducing time on site and as large quantities can be bundled and loaded effectively, each lorry delivers a vast roof area, reducing the number of vehicles to site, not to mention all associated traffic, unloading and storage activities.  Roof deck  is a solution to the negative environmental impacts of a construction site – reducing noise, emissions, traffic congestion and more importantly our carbon footprint.

Energy use

These substantial sustainability benefits pale into insignificance, compared to the benefits gained over the life of a building, by utilising metal deck sustainable roof design. It is commonly accepted that the embodied energy in a building is approximately one tenth of the energy used in that building over a period of 50 years. The impact of including a highly insulated, well sealed metal deck roof can be a reduction in heat loss through the roof by half.

Green Roofs

However it’s not just about carbon and energy, metal deck green roofs offer far more than just that.

• Slows the run off. They reduce the amount of rain that runs off the roof and they slow down the peak rate of runoff by several hours, which in turn dramatically reduces flooding and the burden on the drainage system. The water is cleaned as it percolates through the layers.
• Habitat for wildlife. They cool the surrounding air as well as the building they are on and they provide a safe habitat for plants, bees, butterflies insects and birds.
• Feel good factor.  Green roofs look good in any work or home environment and encourage wildlife.
• Economics. Green roofs reduce the need for air conditioning and heating so they save money.
• Planning benefits. Many councils now insist on the inclusion of green roofs in building developments.

As a recent example, the UK’s largest and greenest sustainable storage facility at Adnams Brewery used a metal deck green roof with a Corus Panels and Profiles D159 under a Sky-Garden Greenroof to reduce the visual impact of the building on the landscape and to regulate the internal temperature. A drip irrigation system was installed to sustain the plants.

Corus Advocates The Right Choice, Not The Light Choice!

Designers and contractors need to be aware of the high risks and potentially catastrophic consequences of using lighter gauge steel liner profiles in site-assembled building envelope systems.

The drive to cut costs is increasingly leading to the selection of liner profiles made from inferior materials that do not meet non-fragility standards and could even lead to a loss of life, if used as a working platform during construction.

To encourage correct specification and procurement practice and promote site safety, Corus Panels and Profiles has just published an article entitled “Make the right choice, not the light choice”.

Click here to download a PDF of the article.

Click here to download the Colorcoat® Technical Paper on steel gauges and the building envelope.

New Technical Paper from Corus – Gauge

Corus has published a new technical paper regarding the importance of  the effect of gauge on pre-finished steel roof and wall cladding performance. The paper takes an in depth look at the implications that using a lower gauge will have on the building envelope and how to clearly specify gauge. The paper is available to download from the colorcoat-online website here

ComFlor® Colorcoat® and Closed Ends

Colorcoat®

Union Square, Aberdeen, using Comflor® 80 Colorcoat®

Uniquely for composite floor profiles ComFlor® 60 and ComFlor® 80 can be manufactured with Colorcoat® Exterior Flexible Polyester coating to the underside. This is suitable for situations where a visibly exposed soffitis required, such as in multi-storey car parks or in schools, offices and any application where the benefits of thermal mass are required. The ComFlor® soffit can be left exposed or where further protection is required it can form the base coat for further protective systems.

• Suitable for multi-story car parks
• Attractive visual finish for an exposed soffit within any heated building.
• Allows the full benefits of thermal mass to be used.
• Colorcoat® surface finish is highly efficient at heat transfer

Comflor® Closed Ends

ComFlor® 60 Closed Ends

Closed ends are available on ComFlor® 60. Produced on line during the roll-forming operation, closed ends both allow the wet concrete to be retained without the use of filler blocks and give a continuous mass of concrete above the beam flange.

• Ideal for single-span construction
• They permit in factory shear stud welding – removing the need for onsite stud welding
• Solid concrete behind the closed ends give acoustic reduction over dividing walls
• Intrinsic fire stopping is also provided
• Allows solid slab shear stud values

For more information on both products, visit our website.

New Building Envelope Case Study : Eddie Stobart

I’ve just uploaded a new case study to our website: Eddie Stobart in Widnes.  This project uses 12,000m2 of Trisomet® 333 Insulated panels in white. Its certainly an impressive case study and we’ve got some great photos which you can view by clicking on the gallery tab. You can also download the full case study as a PDF on the page.

To view the case study, click here