Case Study:Stone Stucco Repairs On Grade II Listed Kensington Property

Introduction

This property in Kensington Garden Square is currently undergoing comprehensive redecoration works. While abseiling and painting the property’s façade, our operatives noticed a cracked area in the stucco. The cracks had been painted over multiple times, creating a thick layer of paint, making the damage difficult to spot until our team inspected it closely while abseiling.

Kensington Garden Square, built in 1692, is located in the heart of West London. These beautiful period properties exhibit some of the most iconic London architecture, with houses 1–45 being Grade II listed for their architectural and historic merit.

The Project

Unfortunately, the original stucco had snapped off on two corners of the stone ledge. One corner was recovered, but the missing piece from the other side had been lost over time. The cracking in the stucco had occurred due to years of freeze-thaw damage from water collecting on the ledge, which had severely eroded the corner pieces.

Our team was tasked with restoring these areas of lost stone, using the original pieces where possible, and colour-matching the repairs to the rest of the building.

The Logistics

We had previously worked with this surveyor, who recommended our property restoration services, knowing we could complete the necessary renovations without scaffolding, which was a priority for the residents.

While rope access had been used to restore the rest of the property, this project required a stable surface for the stone repairs. We arranged the necessary permits and coordinated with residents to ensure sufficient space for our cherry picker, allowing our team to access the damaged areas of the stone. By using our 27-metre van-mounted cherry picker, our team could safely reach the work zone without the risks of falls or strain associated with working on ladders. We established safe working zones at ground level by using exclusion barriers to protect pedestrians and create secure areas for the work below.

Our Solution

Thanks to Spectrum’s extensive knowledge and experience in stone care and repair, we were able to provide the client with a detailed and comprehensive remedial proposal. This plan was approved and executed by the same team already mobilised on site. The stone restoration work was completed in just two days, with the repairs and moulding carried out on the first day, followed by final sanding and colour-matching on the second.

On day one, the recovered original stone pieces were bound together using Stonehealth’s Stone Repair Kit. Any missing stone was remoulded using a stone repair resin mixture, which can be sculpted for 20-30 minutes before setting. As no original pieces of the ‘art stone’ remained on the other corner of the ledge, we hand-moulded a replacement corner to match the surrounding areas. Both pieces were then roughly sanded and ‘helifixed’ onto the original stonework. These metal bars help hold the new pieces in place, providing additional structure and stability for the repairs.

Once the repairs had cured and were securely attached, they were finished with a final coat of stone repair material to ensure a seamless blend into the original stonework.
On day two, the repairs were sanded down to smooth the stone repair compound. Two coats of Zinsser paint were then applied to match the rest of the property. Many listed properties specify the use of Zinsser or Keim paint for redecoration due to their high-quality and long-lasting finishes. These paints help preserve the longevity of historic buildings like this one.

Due to the complexity of the project and the skills required for the repairs, our team carefully chose the most suitable access option. The height and location of the work made ladder access impractical and unstable. Therefore, a cherry picker was the best choice, providing a stable, level platform and a safe working environment, with minimal disruption to pedestrians and residents.

Challenges

One of the challenges we encountered was the possibility of asbestos on the property. Due to the building’s age, the materials used differ significantly from modern ones. One key difference in Victorian stucco is the inclusion of fibres within the render layers, likely used as a binding agent. Older stucco was typically applied in three layers, with the final layer consisting of a Portland cement mixture.

Where the corners of the original stucco had snapped off, our team noticed fibres within the exposed layers. Whenever fibrous material is found on a building site, it is essential to rule out asbestos, which poses significant health risks. When working on older buildings, documentation on the materials used can sometimes be limited.

This is not usually an issue, but when fibrous materials are present, asbestos becomes an immediate concern. It is crucial that all team members remain fully informed and briefed throughout any asbestos investigations to ensure their safety. We paused work while awaiting the results of the asbestos report. After receiving the all-clear from the specialists, we resumed the stone restoration service. Asbestos is a serious consideration that had to be prioritised within the project’s timeline. Fortunately, in this case, it was a false alarm.

The Results

With Spectrum’s depth of knowledge and experience in stone care and repair, we could provide a detailed remedial proposal, which was agreed upon and carried out by the same team already mobilised on site. This prevented further damage while the broken stone remained exposed.