Surely a better way of supporting M&E Building Services on flat roofs?


12 May 2015

Laurence James of ‘Pump House’ in Nottingham looks at how mechanical and electrical contractors are changing their views on the best practice in supporting rooftop M&E building services by favouring independent and non-penetrative support systems now widely available across the UK.    

If you have ever been up on a flat roof where there are old existing building services in-situ, it should be all too clear that the traditional manner of supporting these services is often less than ideal these days.  The question now is whether these traditional methods of casting concrete plinths, building brick piers or manufacturing steelwork are becoming a thing of the past?
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Old heavyweights

Traditional concrete plinths require shuttering works prior to concrete pouring, with additional waterproofing layers to be added following this.  With brick piers curing times and separate trades are also required. 

​Alternatively, steel plinths which break through the waterproofing membrane and insulation down to the structural roof can cause inherent risks themselves, such as potential cold bridging issues, and may affect current Building Regulations Approved Document Part L energy reduction figures.

It goes without saying that the time-frame and differing trades required to carry out such ‘old’ traditional detailing can have an adverse effect on the smooth running of building contracts.  Potentially, there is the risk of delay should, for example, there be ingress of water through an area of extra waterproofing detailing carried out to these plinths.  

​Lighter alternatives 

The problems may be compounded in that traditional practices can cause headaches for the building owner or end user in respect of future upgrading of their flat roof insulation.  If replacement of the existing building services becomes necessary, in favour of smaller, more high-efficient equipment, it can lead to the new items not fitting upon the original plinth locations at all!

It is of little surprise then that we are seeing greater emphasis on utilizing the non-invasive, independent and lightweight supporting products available in today’s market? These proprietary products are typically manufactured from mild steel strut or box sections that are hot dip galvanized to produce frameworks which support building services. 

The frameworks manage the imposed loading down through their polypropylene, plastic or rubber feet which are square, rectangular or round in fashion; these in-turn sit on the finished waterproofing layer or upon the insulation boards within an inverted roof design.
Since the advent of independent support systems, introduced into the UK back in the mid-nineties, contractors, specifiers and consultants alike are realizing that these lightweight solutions negate many of the traditional elements and overall provide greater flexibility, whilst reducing unnecessary risk of delays to the project program.

​Why change?  

One would suggest that the key to the rise of such products is their simplicity?  Lightweight non-penetrating solutions that can be manually positioned at the last minute, without being set within a pre-determined location dictated early on in the project works. They provide the installer with a fully flexible solution that ultimately is quick and simple to install with little, if any, training required.

As mentioned they negate the requirements for often awkward and time consuming waterproofing detailing, avoiding cutting through the insulation layer causing thermal deficiencies and potential interstitial condensation complications.  These independent frameworks are robust enough to manage the heaviest building services such as large chillers and packaged plant rooms quite satisfactorily.

​Considering the risks 

However, these support solutions can come with some inherent risk themselves.  What with a plethora of support systems now available to purchase through many different companies within the UK, the installer should not lose sight of key considerations associated with such systems.   

In the very nature that these solutions are lightweight and independent, they can be susceptible to wind loadings, particularly in exposed areas such as high rise buildings or coastal environments. Therefore guidance and, if necessary, wind loading data should be sort from the manufacturer of such systems prior to delivery. 

Another factor is when heavy services, such as packaged plant rooms, large chillers and air-handling units, have concentrated loads which need to be managed to ensure the roofing insulation within the roof build up is not compromised and compressed.   

​Again, creditable calculations relating to foot pressures, leg reactions and roof loadings ought to be a prerequisite, and a sound knowledge of modern-day flat roof designs and insulation types should be mandatory to ensure there are no inherent damaging effects to the roofing build-up post the installation of framework and plant on top. 

​Support for the support 

Above all, when the consumer makes their selection on which supporting system to purchase, they should ensure they are automatically receiving the technical support, long term experience and professional advice by the product manufacturer.   

The manufacturer should automatically give consideration to all aspects associated with the support system namely, the roofing build-up beneath, the imposed roof loadings and foot pressures and wind load management.  Maintenance & Service manuals for the support system should be available for inclusion within the end user/building owners’ Operation & Maintenance manuals. 

With all factors considered and selection made these alternative solutions are clearly the way forward for future projects that require mechanical and electrical building services supported on flat roofs.  Speed, simplicity and robustness are key, and it is of no surprise we find ourselves working within an industry that chooses more often than not to use such systems over outdated traditional methods.  After all time is money!