Project Case Study Allen Court, UB6 0JZ

Project Information

  • Project Address: Ridding Lane, Ealing, UB6 0JZ
  • Client: Lindon Homes
  • Duration: January 2016 - July 2016
  • Value: £790,000
  • Scope: Asbestos removal, temporary works installation, deconstruction from 11th - 4th floor, demolition from 4th to ground, ground works & concrete crushing
“This contract is a great example of the Downwell philosophy. We pride ourselves on not doing what is easy but doing what is right,” Matt Phillips Managing Director of Downwell.
11 Storey Large Panel System (LPS) Tower Block

History of Large Panel System

Ronan Point is a name that will live long in infamy in construction history. In May 1968, a 22-storey tower block in Newham, East London partially collapsed when a gas explosion demolished a load-bearing wall, causing the collapse of one entire corner of the building. Four people were killed in the incident, and 17 were injured. That collapse led to complete loss of public confidence in high-rise residential buildings, and major changes in UK building regulations resulted. In particular, the so-called “Large Panel System” design used at Ronan Point fell into disrepute, the collapse having been attributed directly to the implementation of this construction method in which prefabricated concrete parts are lifted into place by crane and joined together in-situ.

Ronan Point partially collapsed following a gas explosion

According to a Government investigation into the disaster, the Large Panel System design of Ronan Point (and several similar tower blocks across the nation’s capital) was not adequate to withstand even small explosions, as proved by the actual collapse; was not adequate in a fire during which the building was likely to bow; and was note even adequate to withstand expected wind loading. Indeed, it was suggested that—in a high wind - wall panels could be sucked out, leading to collapse.

Since that collapse, the remaining Large Panel System blocks have been strengthened and reinforced. And those that have reached the end of their practicable and functional life have been demolished with the fate of Ronan Point an ever-present consideration.

Investigations & Planning

There was one major consideration that would need to be addressed before the project method could be fully designed. That was that Allen Court was standing a mere 18m away from the Piccadilly Line

Our 3D representation of our intended method is a great way of showing our intentions to the client.

Once Allen Court had been awarded to Downwell it would take take several months of investigations and planning before deciding the best approach for the project. After completing structural investigations and advice from engineers the preferred demolition method would be the reverse construction method which is the most widely used method for demolishing buildings of this construction.

Our 3D illustrations to communicate how we intend to deconstruct the building

This method involves encapsulating the building with scaffolding, installing diagonal bracing on the individual panels and then deconstructing the building starting from the top down.

Asbestos Removal

Prior to the demolition works commencing the building would have to firstly be surveyed for asbestos containing materials (ACM's). This survey is called a demolition and refurbishment survey and involves intrusive investigations throughout the building to ascertain the presence and then the extent of any asbestos materials.

The asbestos was identified to be both the licensed and non-licensed varieties. The licensed asbestos is removed using fully controlled conditions. The non licensed asbestos is removed under semi controlled conditions.

Removing asbestos under fully controlled conditions

Inner City Environmental were appointed to remove all of the asbestos containing materials from the building prior to the demolition works. They are a fully licensed asbestos removal contractor with years of experience working on large scale demolition projects. They were given 12 weeks to complete the removals over the 11 floors of the building.

All of the ACM's were removed from the structure which included the removal of vinyl floor tiles, asbestos insulating board, asbestos rope, asbestos gaskets and various asbestos cement products.

Scaffold Erection

To aid with the demolition the entire building needed to be encapsulated with over 2800m2 of tubular scaffolding. We appointed Inner City Scaffolding to provide the scaffolding needs for the project. This included encapsulating the building with debris netting on 3 sides and then Monarflex on the 4th side that is facing the Piccadilly Line. This is designed to prevent dust and small fragments from leaving the scaffold.

The scaffold would also provide the required access to the floors whilst the building is being demolished. Ladder access points on the rear of the building meant that the building could be safely vacated in the event of an accident.

The debris fan used for the protecting the access road

A debris fan was required on the south elevation of the scaffold. This fan was required to provide additional protection to the access road that runs up the side of the building. This access road was to remain open during the demolition as it is the only access to the residential properties to the north east of the site.

As the building is reduced open edges are always created which causes the potential to fall from height. Inner City Scaffolding were on hand throughout the project to constantly erect and adapt hand rails to ensure that the workforce on the building were always safe.

Erecting the scaffold a floor at a time

As the building is deconstructed a floor at a time the scaffold will be progressively struck whilst working in harmony with Downwell. Inner City Scaffolding were constantly on site to ensure that the scaffold could quickly be adapted around the deconstruction works. The scaffold was always kept one lift above the deconsruction works to ensure that the works were safley contained and nothing could leave the footprint of the building.

Soft Strip

Prior to the demolition works commencing and with the building now being free of asbestos the internal fixtures and fittings from the building need to be removed. This includes all soft furnishings that would have been left behind by previous tenants.

Soft furnishings to be removed prior to structural demolition

All of the arisings created during the strip out was transported to the ground floor via the lift shaft. Once on the ground floor the different waste streams were separated and loaded into their dedicated bin for recycling.

Stripped back to the structure

The main purpose of the soft strip element is to ensure that the concrete arisings during the structural demolition phase remains clean and free from other materials. It also helps with the programme as removing the soft furnishings prior to the structural demolition is quicker and easier than removing it from the concrete arisings.

Reverse Deconstuction

The most crucial part of the approved method for demolishing LPS buildings is to adequately prop the panels that make up the walls of the building. This was is to prevent the domino effect once the panels are started to be removed. On the external panels, props with adjustable heads were secured to each panel and floor using six resin-anchored bolts. Holes were then created between the panels’ reinforcing bar to allow chains to be affixed to crane chains.

A 90 tonne crane ensured that the panels did not move while they were cut out of place using a mini excavator equipped with a hydraulic breaker. Once the panel had been cut along both the vertical and horizontal joints, the crane lifted the panel out, lowering it to ground level for further processing.

Deconstructing the building one panel at a time

This process was then largely repeated on the internal panels. Following a detailed structural survey to determine the type and quantity of propping required, holes were once again created in the internal panels between the reinforcing bars within. Chains were then passed through the panels with the crane taking up those chains while a mini excavator cut around the perimeter of the panel. Once it was broken free, it was lifted to the external processing area.

All of the panels were then processed using a demolition excavator with munching attachment. This attachment munches the concrete free from the reinforcing bars so they can be separated for recycling. The concrete is then loaded away into tipper lorries and taken to a recycling facility. Following the removal of all the above ground arisings the foundations are removed from the ground down to a depth of 2m. This material is then processed and removed from site for recycling.

“Every Downwell Demolition project begins and ends with the safety of local people and the safety of our workers. Having analysed the Large Panel System construction of Allen Court and having looked at the condition of the building, we believed that a controlled deconstruction was the safest and most effective demolition method.” Matt Phillips.

Ultimately, the demolition was completed ahead of the scheduled 36-week contract duration, with zero reportable incidents, and whilst achieving a recycling rate of more than 98.5 percent.

Update 23/8/2016

We are pleased to announce that we have been shortlisted in the World Demolition Awards for this project. The category we have been shortlisted in is "Contract of the Year Under $1 Million" The award ceremony is to be held in Miami, Florida in October 2016. We would like to take this opportunity to thank the project team for their excellent work on this project. They excelled in ensuring that this technically challenging project was brought down safely and way within the allotted programme.

Created By
Matthew High

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