GRC Cladding panels have become more and more popular choice as an architectural finish material. People consider Glass fibre reinforced concrete as a relatively new type of construction material. Although, the construction industry has been using it for over 50 years it’s only getting more attention in the 21st century. GRC is very versatile and that is why it’s gaining popularity among architects and specifiers. Due to its high elastic properties designers use GRC cladding in solutions where resistance to live loads is necessary.
GRC cladding systems require high quality standards in manufacture and meticulous record keeping. If you use glass fibre reinforced concrete cladding or panels in your projects it is important to employ subcontractor or installation crew with GFRC cladding experience.
Our previous article concentrated on the processes which were mostly carried out off site. This post will focus on works in relation to the GFRC cladding installation on site.
How to install GRC cladding panels?
It’s not easy to answer such question in a short way. Every project is different and every design is different as well. However, there are some common parts which you can apply to various GFRC cladding projects.
Before you start with any installation be sure that your design is verified against compliance with the project specification and architect’s requirements. It is not enough just to get design acceptance. You should also make sure that you can meet all the testing criteria. What is more, it is crucial to check how easy or how complicated it is to build GFRC cladding according to the design. For such an activity you can build a mock-up or a prototype.
Safety documents for GRC Cladding panels installation
The first step for us, prior to any work on site, was working out the methodology of installation of GRC panel cladding. Later it naturally led to preparation of suitable safety documents. For this task we engaged with our client. We visited the site to get familiar with the access, egress, transportation routes and installation area limitations. With over 300 types of different types of GRC panel cladding panels we had to take every step of transportation and handling into consideration. It was crucial to plan how to build suitable timber crates. Additionally, we planned how to fit these crates around every corner of the construction site until these are transported into the final installation area.
Lifting equipment for GRC cladding installation
After we acquainted ourselves with the site we were able to select the suitable access and installation equipment. Some of the GFRC cladding panels weighted over 50kg and were not suitable for manual handling. Thanks to our colleagues from the Research & Development department we identified a few pieces of lifting equipment that were just right.
There were also several GRC cladding panels weighting around 180kg.
We decided to use Winlet 575 machine manufactured by Wienold. Our partner in lifting equipment, Hird, supplied it, maintained it and repaired it for us. They also installed a custom frame with suction pads in Winlet machine.
Hird supported us from the very beginning of the project. They tested several frames and different types of suction pads. We had to make sure that we meet all safety requirements for the installation of GRC cladding panels.
Thanks to an electric forklift from Jungheinrich we were able to handle and install the heaviest panels with the weight of 600kg.
Survey prior to the GFRC installation
Another important step for GRC cladding installation is survey of the fixing area.
We recommend to do it prior to the design work in the locations where GRC panel cladding and substructure will be installed. It is necessary to understand the fixing ground and tolerances of the installation area.
Whether it is an internal cladding panel or a façade panel you should follow the setting out and relation to the architectural grid lines.
Our colleagues from Noack Engineers carried out series of surveys which included scanning of raw tunnel structures and also scanning of as built position of MEP items.
The surveyors used various pieces of equipment like Trimble S7 station.
In some instances we carried out concrete reinforcement survey. Our client did not want that we drill through the rebars. Therefore, we mapped out the position of reinforcement with ground penetration radar with the help from Sandberg surveyors. Afterwards the operatives drilled in between the surveyed rebar locations.
Designing around the tolerance issues
Why is this relevant? If you fix your GFRC substructure to the tunnel walls you want to ensure that these walls are in the place where they should be. If these are installed out of tolerance it can cause installation issues.
When the walls deviate and are further back to the designed position it may require different substructure and fixing method. Increased distance can involve higher loads affecting the substructure.
On the other hand, when the walls are in front of the designed position it may mean that the GFRC panels and substructure will not fit or will clash with other elements.
This should also be checked with building or structure fire regulations. Some buildings require specific dimensions for the escape routes. s
If you install GFRC cladding on a wall which is in front of the designed position you may interfere with the escape route. What is more, such installation may cause clashes with other structural or architectural items.
Due to the potential issues arising from the fixing ground tolerances it is important to design some sort of adjustment in the GRC wall panel cladding system. This way you can accommodate tolerances from survey and manufacture during the installation phase.
Once we completed the survey of the installation area it was time to analyse the collected information. It was a desktop exercise and we overlaid point cloud with the architectural 3D model. Our designers spotted the areas which could cause installation issues and designed suitable custom solutions for almost each case.
In some instances it was not possible to overcome the out of tolerance issue with our design. Where the tunnel wall was over-sprayed and too much in front of the designed position it had to be scabbled back locally.
Setting out prior to GRC panel system installation
After the fixing area was prepared for installation our surveyors returned to site for setting out works. Using co-ordinates from the architectural design they marked centre lines of the substructure frames and location of the fixing points.
Safe access for GRC panels works
When it comes to access to work area we had to consider several options. Different parts of the site required different access. We worked on platforms and in the tunnels where we utilised scissor lifts or podium steps.
Scissor lifts were supplied by Star Platforms who offer great service in terms of quick operations and large fleet available. They always had an engineer close by the site and were able to react in a swift manner to any repair and maintenance needs.
Another area which caused access issues were escalator shafts. We worked there before the installation of escalators and afterwards. In these areas we used several means of access such as PASMA towers, escalator towers, incline hoists with working platform and standard tube & clip scaffold.
Installation of GRC cladding panel substructure
Our substructure arrived to site almost like flat packed furniture from IKEA. This allowed us to minimise the amount of deliveries and to reduce carbon footprint caused by the delivery vehicles. We assembled the components on site in a small pre-fabrication area. GFRC substructure sections were transported to the installation area manually or on trolleys.
In order to install GRC cladding subframe we had to fix several thousands of anchors into the sprayed concrete lining.
Our installation team had to control several setting parameters like edge distance, bolt to bolt distance and drilling depth.
For this instance our structural depertment carried out structural analysis in order to determine applicable loads affecting the substructure.
Our customer had another issue, they didn’t want us to penetrate through the waterproofing layer which was approximately 200mm under the face of the sprayed concrete lining.
Installation of concrete anchors
Once we recognised the loads and dimensions we were able to select suitable anchors. This time we chose Hilti expansion anchor – HST3-R for most of the locations.
Installation of these anchors was kind of a project on it’s own. Correct setting of the anchors required detailed planning, installation team training and quality checks in several steps.
Our operatives torqued each anchor to the required level with a calibrated torque wrench. For example, the torques for M12 anchors were 60Nm and for M16 – 110Nm.
Pull out test for GRC panel cladding substructure fixings
What is more, our customer required that we test our anchors for pull out. This requirement followed Construction Fixings Association (CFA) guidance note for site testing construction fixings – 2012.
We studied CFA requirements and carried our structural calculations. Afterwards we determined that the pull out load in the tests should be 10kN.
There were several instances where GRC cladding substructure consisted of heavy steelwork. Our structural department calculated loads for pull out tests individually and some results reached to almost 50kN.
An accredited test house carried out the pull out tests on site. In our case we selected CRL – Concrete Repairs Limited who attended the site several times with various pull testing equipment. For most of the pull tests we used small and compact testing equipment – Hydrajaws 2000.
In all the tests there was only one single failure. In this case the anchor was cut flash with the concrete substrate and another anchor was installed away from the disengaged anchor. Afterwards, another pull out test was successful.
Details of handling and installation of GRC cladding panels
Once we installed the substructure and levelled in the next step we wanted to install GRC cladding panels. The logistic team delivered GRC cladding to site in timber boxes, offloaded with a telehandler and moved with a crane or hoist to the actual installation area.
The weight of boxes varied depending on the size and shape of GRC cladding panels. Some packs included smaller panels with the total weight of approximately 300kg and there were several panels which weighted almost 600kg each.
Operatives moved timber crates with GRC cladding panels on site with a pallet truck (by Aplant). We removed lighter panels (below 50kg) manually from the boxes and later moved these either on a scissor lift or on a scaffold tower.
GRC cladding which were heavier than 50kg were moved with WinLet equipped with suitable suction pads. Operatives who worked with the glazing robot attended familiarization training prior to site trials.
WinLet glazing robot allowed for easy handling of GRC cladding. For example we could remove heavy panels from the storage box, rotate it, move it and install it on the substructure.
Preparing GRC wall cladding panels for installation
Some GRC cladding panels required extra assembly of some parts, for example acoustic panels. Operatives on site installed the sound insulation from Rockwool, secured it in a panel and also fixed an inspection cylinder. This part allows for inserting boroscope through the panel for visual check of the substructure and elements behind the cladding without removing a single GRC panel.
GRC panels included cast-in plates with a hook on notch. This allowed for the panel to be hooked on the subframe without additional moving parts.
Safety tethers and locking mechanism provided additional security for GRC panels.
When operatives put the panel on the subframe they aligned it and set the panel in level.
In several instances we surveyed cladding in reference to the project grid-lines and datum level. If a GRC panel was too high or too low we adjusted it to follow the architectural specification. We followed these architectural requirements which you can find in the GRCA specification.
On-site repairs of GRC wall panels
It is nearly impossible to handle such a high quantity of GRC panels in a tight environment and do not make any scratches or damages.
Different trades or access equipment occasionally hit, scratched or chipped some of the panels. With all the small damages it is possible to make local repairs on site.
We developed a suitable repair procedure and a team of trained operatives worked on fixing the minor damages.
Quality Assurance during GRC panel cladding installation
Our customer and the end user of the facility had high quality standards. Quality engineers inspected each step of installation and recorded their findings in the installation QC check sheets.
For some of the quality checks our client witnessed the installation or inspections with third parties. For other steps we documented the process and and the client checked the paperwork.
We supported our customer with random checks as well. This included torque test of fixings, pull out tests and survey of specific parts.
Our client had also carried out his own quality surveillance of GRC Cladding. We presented the results of such inspection in a report with detailed description and photographic evidence.
Of course we had do some snagging works and re-inspect the GRC panels.
GRC (also GFRC) is glass fibre reinforced concrete. This type of concrete uses alkali-resistant glass fibres instead of metal reinforcement.
Main characteristics of GRC are high resistance to live and dynamic loads. It is much more flexible than standard reinforced concrete. In certain conditions it is more resistant to cracks when compared to standard reinforced concrete.
Due to its high flexible strength construction companies predominantly use GRC as parts of facades, GRC cladding panels, permanent formwork, building restoration elements, street furniture, GRC planters, electrical cable covers, planters and many other sectors.
GRC elements present higher flexural strength tan pre-cast concrete. GRC manufacturer replaces standard reinforcement with thin and light glass fibres which add to the bending capabilities of GRC elements. Pre-cast concrete elements require minimum concrete cover for reinforcement depending on the concrete exposition class. Usually it’s minimum of 20mm up to 50mm concrete cover. This cover is necessary to achieve proper bonding between reinforcement and concrete and also to protect reinforcement from corrosion due to water ingress and moisture. This concrete cover around reinforcement makes the pre-cast concrete panels heavier than GRC elements. GRC can be thinner and lighter in weight which reduces the overall dead load of a specific element or the whole building or structure. Additionally, thanks to higher flexural properties GRC can withstand higher live and dynamic loads.
It’s a type of concrete that uses alkali-resistant glass fibres as reinforcement instead of standard metal reinforcement.
GRC panels are elements of GRC in a designed shape and you can fix these into a substrate by adhesion or mechanical fixings. For example these can be square, rectangular, trapezoidal or round. Architects usually define the size and shape of GRC for each particular project. GRC panels can create standalone cladding or can be a part of unitised façade or cladding system.
GRC cladding is the secondary skin of a building or structure consisting of GRC panels and supporting structure. GRC cladding elements installed on steel stud frame enable production of a lightweight and strong architectural GRC cladding systems. According to Designing Buildings Wiki GRC can be 80% lighter than pre-cast concrete with steel reinforcement and therefore can achieve BREEAM A+ material rating.
Specialists GRC manufacturer usually makes GRC from portland cement, silica sand, other aggregates, water and alkali-resistant glass fibres which will never corrode as oppose to the standard ferrous reinforcement. Oftentimes, the manufacturer uses additives in the GRC mix like plasticisers or pigments.