Built Up Roofing & Cladding Systems


[wptab name=’Overview’]

Overview of Metal Built Up Roof Systems

Built Up roof and cladding systems have been used for around fifty years in the UK and involve profiled steel or aluminium thin-gauge metal sheets. These metal sheets can be taken to form a liner sheet and an external sheet, which are separated by a spacer system to create a cavity for insulation. Modern built up systems use more complex spacer bar systems designed specifically to reduce cold bridging and enhanced structural performance to accommodate the depth of construction typical of modern buildings.

Metal built up roof systems have been used in the northern hemisphere for many decades, driven by the government regulations to keep heat within a building and to minimise the energy used to create that heat, thus reducing the associated carbon emissions.

With the new south african government standards, SANS 10400 XA legislation, the search for energy efficient metal roofing & cladding systems has certainly begun.

MRC has the experience to specify, deliver and install ‘new build’ energy efficient metal built up roofing & cladding systems that will satisfy a long list of performance criteria such as:-

Thermal performance to a staggering market leading 0.10 W/m²K or even better if required.
Sound attenuation as high as 60 dB Weighted Sound Reduction.
Sound absorption for swimming pools and schools to stop sound reverberation.
Specialist roof systems for high humidity roof systems.
Specialist roof systems for high security performance – Prisons, Data centres, Governmental Buildings.

MRC Group’s Over-Roofing or Over-Cladding solution provides the opportunity to upgrade / refurbish an existing building envelope without having to remove the existing metal or asbestos roof or cladding system. The system is generally considered when the existing roof is either leaking or coming to the end of its operational life.

The patented AshGrid™ System is installed in the troughs of the existing steel profiled roof sheets or asbestos roof sheeting, with the brackets fixed directly to the underlying steel or timber purlins, thus creating an engineered, structurally defined cavity between the old and new roof coverings. When insulated this cavity dramatically improves the overall energy efficiency of the entire building.

MRC Group’s installed over-roofing system, is backed with the unrivalled single source ‘Guardian’ System Warranty which covers design, materials, installation & maintenance for the term of the roofing and cladding system.


[wptab name=’Features & Benefits’]

Key Features of Over-Roofing Systems

  • No requirements to remove the existing asbestos or metal roof system therefore the property can continue to operate while works are undertaken
  • Full range of aluminum and steel ‘Secret’ & Pierce Fix roof and cladding systems
  • Option of increasing the R-Value performance up to 10 (m2.K/W)
  • Minimum disturbance to the use within the building
  • Avoids the costs of stripping and disposing of existing materials
  • Excellent sound reduction & anti-rain drumming performance
  • Opportunity to increase the roof pitch with differing bracket sizes
  • Backed with the up to 20 year ‘Guardian’ System Warranty


[wptab name=’Applications’]

Applications of Over-Roofing Systems

Over-Roofing Systems have been used throughout the world for over 20 years providing roofing & cladding retrofitting and refurbishment solutions for leaking roofs or property envelopes that have come to the end of their operational life.

Whether the existing roof system is constructed from metal or asbestos, or the structure is steel or timber, over-roofing & over-cladding provide the perfect solution to the refurbishment of operational property.

If the original design of the roof system has been designed too low, then the over-roofing system provides the perfect opportunity to increase the pitch of the roof slope minimising wind driven water ingress.

  • Industrial applications such as Workshops, Factories, Food Processing Facilities and Automobile Assembly Property that require the building to operate while the over-roofing system is being installed.
  • Commercial and Retail space such as Shopping Malls and Offices that are always trading and are looking to upgrade their failed roof system energy efficiency to reduce heating or cooling costs.
  • Governmental, Educational, Prison & Transportation Property such as Airports, Schools, Universities, Train Stations and High Security Property that is requires an upgrade in acoustic and thermal performance of their existing leaking roof and cladding system.


[wptab name=’Technical Data’]

Technical Data of Over-Roofing Systems

ASHGRID™ Over-Roofing Spacer Support System

  • Brackets with thermal pads – standard height range from 60 – 280mm (Deeper brackets available on request)
  • Standard Bar lengths from 1.2 / 2.4 / 3.6 Metres
  • 2 No. Self Driller Fixings per Bracket – AshFix Mild Steel 5/16 Hexagonal Head LS25 (Steel Purlins) or TF45 (Timber Battens) Self Driller Fixings, with an integrated 16mm washer flange, fixed through the existing roof sheet into the structure

Optional Insulation for Over-Roofing Systems

  • Full range of insulation types & thicknesses available
  • Fire Classification Class 1 (non-combustible)

Please note that insulation compressed between purlins & roof sheets will lose at least 35% of the proclaimed R-Value, a constant cavity thickness does NOT compromise the R-Value.

The table below provides the R-Values that can be achieved using an over-roofing system.

[table id=1 /]

Acoustic Data – Sound Reduction

  • 0.55mm Steel Roof System 40dB +
  • 0.8mm Aluminium Roof System 42dB +

Weight of a Typical Over-Roofing System based on existing purlins at 1800mm centres

  • 2 No. 135mm Bracket per Ln Metre                   1.0 kg / m2
  • 135mm roll out insulation                                   1.7 kg / m2
  • 55mm Secret Fix / Pierced Fix Roof                   6.0 kg / m2

                                                            Total Weight  8.7 kg / m2

Alternative Over-Roofing Roof Sheet Options to Consider

  • 0.8mm Aluminum Roof System                            4.0 kg / m2
  • 0.8mm Steel Roof System                                    9.0 kg / m2

Over-Roofing System Warranty

  • Up to 20 year, single source ‘Guardian’ System Warranty covers Design, Materials, Workmanship & Maintenance


[wptab name=’Guarantees & Warranties’]

Guarantees & Warranties of an Over-Roofing System

MRC Group’s up to 20 year ‘Guardian’ System Warranty cuts through the myth & mystic of product guarantees and workmanship warranties issued by the construction industry.

Traditionally a product guarantee would be issued by the manufacturer and the workmanship warranty would be issued by the installer of the over-roofing system. Two separate pieces of paper, with differing length of terms and when put along side each other, never answered the question of who will pay for the materials and works such the over-roofing system fail.

‘Guardian’ System Warranty is an unrivalled new era of warranty that covers Design, Materials, Workmanship & Maintenance. The length of term for each element matches and is issued as a single source, transferrable warranty for the life of the guarantee of the over-roofing system.

MRC Group challenges the construction industry to ensure that the workmanship warranty issued by contractors matches the length of term of the supplied over-roofing system, thereby ensuring high quality installations with designed and tested over-roofing and over-cladding systems.


[wptab name=’Downloads’]

Technical Bulletins

Brochure Downloads

‘Guardian’ System Warranty Details

Book a CPD on Over-Roofing


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