Case Study:Night-Time Façade Cleaning and Tap Testing: Oxford Street

We were appointed to carry out specialist external cleaning and façade inspection works at a prestigious commercial property, located just off Oxford Street in central London. Due to the building’s location and high pedestrian footfall, all works were carefully planned and delivered out of hours over two nights.

The Site

The property is a tile-clad commercial building situated in Hanover Square, central London, above a retail unit on Oxford Street. The prominent location required a discreet and controlled approach to minimise disruption to the surrounding area and ensure public safety at all times.

The Client

The works were carried out on behalf of a very large multinational leading client, this was our first job with them so it was hugely important to us to make a good first impression, which we did.

The Challenge

The client required external façade cleaning alongside a condition assessment of the tiled elevation. Given the building’s prominent Oxford Street location, the works needed to be completed out of hours to manage footfall and reduce disruption.

In addition to the cleaning works, the client needed reassurance that the tiled façade did not present any safety risks, particularly the risk of loose or debonded tiles at height. The project combined visual facade improvements with a safety-led inspection, delivered within a tightly controlled night-time working window.

Our Solution

Spectrum Specialist Support proposed a programme of out-of-hours DOFF steam cleaning combined with a full tap test inspection of the front elevation masonry.

The scope of works included:

• DOFF cleaning of the marked-up front façade using high-temperature, low-pressure steam

• Out-of-hours working due to the site location

• Rope access to all required elevations

• Tap testing of the tiled façade to assess adhesion and identify any hidden defects

• Removal and safe disposal of any loose debris

• A photographic completion and inspection report, marked up on a drop-by-drop basis

This approach allowed both the cleaning and inspection works to be completed efficiently while maintaining safety and minimising disruption.

Tap Testing 

As part of the works, Spectrum carried out a comprehensive tap test survey of the tiled façade. Tap testing uses controlled percussion to differentiate between tiles that are securely bonded to the substrate and those that are hollow or debonded.

Solidly bonded tiles produce a clear, sharp sound, while tiles with voids or adhesion failure produce a dull, hollow response. This method allows potential safety risks to be identified without intrusive investigation and helps determine whether defects are isolated or indicative of wider façade issues.

At Hanover Square, tap testing was conducted across the façade to assess condition, confirm safety, and support evidence-based recommendations for future maintenance.

Our Process

The works were delivered over two nights and followed a structured process:

Out-of-hours site setup to accommodate the high-footfall locationRope access installation to safely reach all required façade areasDOFF steam cleaning of the front elevation in line with the specified scopeTap testing of the tiled façade, carried out on a drop-by-drop basisVisual inspection of tiles, grouting, and pointingCompilation of a photographic inspection and completion report

Due to the nature of the cleaning works and the time of night, live cleaning photographs could not be taken; however, post-clean inspection images were captured and included within the final report.

Inspection Findings

The façade inspection identified only minor, localised defects:

• Minor fracturing present to individual tiles on Drops 1 and 2

• Very minor pointing perishing noted in isolated areas near flashing details

• One spalling/fractured tile identified on Drop 5, in slightly worse condition than others

• No widespread spalling, cracking, or hollow areas detected

The tap test confirmed that the tiled façade was in sound condition, with no hollow or perishing areas detected behind the tiles at the time of inspection. As a result, no urgent remedial works were required.

The Results

The DOFF cleaning restored the appearance of the front façade while preserving the integrity of the tile finish. More importantly, the combined inspection and tap testing provided the client with reassurance that the façade was safe and structurally sound.

Three tiles were identified as candidates for future replacement; however, these were not considered urgent. The client was able to avoid unnecessary remedial works while retaining a clear, documented record of façade condition for ongoing asset management.

By combining specialist rope access, out-of-hours working, DOFF steam cleaning, and detailed façade inspection, Spectrum Specialist Support delivered a safe, efficient solution tailored to a high-profile central London location. The works enhanced the building’s appearance while providing the client with confidence in the ongoing safety and condition of the façade.