Over Roofing and Cladding Case Study: Alloa Trade Centre

This case study will walk you through an example of Over Roofing and Cladding as a solution for protecting a Commercial property.

What you will see is a complete transformation into what now looks like a completely different building.

If you have any questions about this particular case study please leave your thoughts in the comments section below or call me on 01592 372573.

Jamie Morton.

The situation

This roof is approximately 40 to 60 years old and is leaking in various different areas.

Over Roofing and Cladding

The original roof prior to work being carried out

Unfortunately there’s no short-term solution for this roof. Certainly we could patch up the holes, but the roof has had many patches over the years and the company have already spent a small fortune on short-term repairs.

The roof is now at the stage where the company will be paying more and more money on an annual basis to continue patching holes/repairs. Over time more holes will develop, and the current patched holes will start to break down because they are only short-term fixes.

In short, they need a more permanent solution for their roof, of which there are two main options.

The solution

There two main options available to us are:

  1. Take the old roof off and replace it with a brand new roof
  2. Keep the original roof and install a new roof over the existing roof (Over Roofing)

Let’s briefly look at both options:

Option 1 – Replace the old roof with a brand new roof

In this specific situation a complete roof replacement poses 5 main challenges, which are:

  1. There are ongoing operations in the building, which would be affected when replacing the roof. This will be a huge inconvenience and impact the indirect costs of the project to the business.
  2. It’s an old asbestos roof, which creates additional costs. As a professional roofing contractor we have to pay to have asbestos sheets removed from the site and disposed of safely and appropriately. We will pay approximately £300 per ton to dispose of asbestos sheets. For this specific project there might have been as much as 50 tons, so there’s at least £15,000 worth of additional cost.
  3. Additional labour costs. Not only would we be replacing the roof, but we have to remove the old roof first. Therefore we would have to build into the project our labour cost for removing the current roof.
  4. When you’re taking sheets off there are multiple health and safety issues because you’re opening up the roof and exposing the inside of the building. There would be additional health and safety considerations, and given weather conditions, may have a direct impact on the operations of the business.
  5. The current single roof materials that have been used make the roof absorbent. This means that the roof absorbs any condensation that is generated due to internal heat. If the roof were to be replaced with a metal roof, there could be additional costs added into the project for internal insulation to minimise condensation.

In short, there are additional financial considerations and a direct operational impact on the business for a complete roof replacement solution, which are mostly eradicated when comparing this to option 2 – Over Roofing and Cladding.

Option 2 – Keep the original roof and install a new roof over the existing roof (Over Roofing)

For this solution the current roof stays exactly as it is, and a new metal cladding roof is installed directly on top. This is commonly known as Over Roofing or Cladding.

There are several advantages for this option, which are:

  1. Operations inside the building can continue as normal, as there will be no external exposure to what’s happening inside the building.
  2. Complications and considerations for working with asbestos roofing materials are minimised as less work is required on the old roof.
  3. The new metal roof completely encapsulates the old roof protecting it from the outside elements and therefore the current problems with water ingress are completely eliminated.
  4. The old roof becomes the inner roof, which takes care of the issue of condensation mentioned in point 5 above.
  5. No further repairs will be required for the old roof, thus drastically reducing the maintenance costs for years to come.
  6. Insulation can be laid between the old roof and the new roof, which can potentially increase the thermal values of the building.

Based on this short summary it’s no surprise that the client in this specific situation opted for the Over Roofing solution to instal a new roof over the existing roof.

How we implemented the solution

1. We installed a proprietary bar system

Alloa Trade Centre - Over Roofing and Cladding

Proprietary bar system

2. We rolled out insulation to increase the U value of the building

Alloa Trade Centre - Over Roofing and Cladding

Rolling out insulation

3. We removed the glass astragals as were perished and we replaced them with GRP translucents

Alloa Trade Centre - Over Roofing and Cladding


Alloa Trade Centre - Over Roofing and Cladding


4. We installed a new roof over the top of the existing roof

Alloa Trade Centre - Over Roofing and Cladding

Over Roofing installation in progress

Alloa Trade Centre - Over Roofing and Cladding

Over Roofing installation complete

Concluding remarks

The option chosen is called ‘Over Roofing’ or ‘Cladding’, which for this project was the most cost effective way to solve the current problem.

There are many roofs on buildings just like this and Over Roofing is likely to be the more effective solution, both financially and from an operational perspective.

In summary, Over Roofing and Cladding was the best option for this project because:

  • the material costs for cladding were lower than full roof replacement.
  • there were less labour expenses to consider because we didn’t have to remove the old roof.
  • there were no direct cost implications for downtime in operations due to the old roof remaining in place.

Photo gallery

As you can see from the photo gallery, once the cladding is in place it is a complete transformation!

Our client’s perspective

We asked our client to comment on the work carried out and this is what they said:

We have owned the Trade Centre Complex for over 20 years, and in that time the building has proven to be a vital asset to our company in terms of the popularity of the units and the strategic location of the industrial units, with occupancy rates at almost 100% year in year out. The downside to the complex, was the roof which was made up of Chrysotile Asbestos. This was built around some 300 Georgian wire glass skylights that for the most part were cracked and heavily soiled and severely restricting the amount of natural light from entering the building. The building is around 50 years old and over the years, the roofing had been needing increasingly more attention to prevent water ingress.

We decided that the time had come where we had to invest in the roof to future proof the building for decades to come. The decision was made to put the contract out to tender, where we invited three companies to tender for the contract. The contract of works consisted of cleaning down all of the existing asbestos sheeting, removing all existing skylights, installing new Polycarbonate skylights, overlaying glass wool insulation over the entire roof and finally clad over the entire roof with a metal profile sheeting, with all associated cover caps, ridge profiles and enclosures.

After the tender quotations were received, we decided to award the contract to Industrial Roofing Scotland.

Due to the duration and scale of the work involved, we commissioned a CDM coordinator who while working closely with IRS, prepared a construction phase plan, health and safety package along with all relevant Method Statements and Risk Assessments. This was then notified to the HSE using the F10 form as legally obligated.

The contract start was agreed and IRS were on site as promised and agreed. From our company’s perspective, the work was carried out according to the schedule and to a very high standard whilst routine auditing of the work was carried out by myself. The logistics of the work meant that there was always going to be a degree of difficulty in carrying out such a large construction project, whilst working alongside our tenants who carried on with their businesses with minimal disruption. Overall, the project went very well with IRS meeting all H&S requirements whilst leaving us with a job completed to a high standard.

We have now instructed IRS to carry out another cladding job and have every confidence on their ability to leave as good a job as the one left at the Trade Centre.

– Steven Dalgleish, Maintenance Manager