RESIDENTIAL BUILDING RENDER CLEANING & ALGAE REMOVAL

The Pond House - Gloucester, GL1

Client's Challenge

The owner of Pond House Apartments contacted APT ICC to restore the external appearance of the building, which had become heavily affected by algae growth and surface contamination.

The white K-render elevations were discoloured by organic growth, detracting from the overall presentation of the property. In addition, a rendered boundary wall was suffering from severe render flaking and deterioration, requiring preparation ahead of planned re-rendering works.

The project required two distinct approaches: gentle cleaning of the main elevations to preserve the render, and controlled removal of failed material from the boundary wall.

All works needed to be carried out while the building remained occupied.

Assessment & Planning  

APT ICC met with the client on site to review the rendered elevations and boundary wall separately, assessing surface condition, contamination levels,
and access requirements.

The assessment confirmed that the main building render required a non-abrasive cleaning approach to safely remove algae and restore appearance. The boundary wall, however, showed significant render failure and flaking, requiring mechanical removal rather than cleaning.

The proposed methods, sequencing, and expected outcomes for each area were discussed and agreed with the client prior to works commencing.

    Methodology

    Render Cleaning – Main Building Elevations

    The main rendered elevations were cleaned using a gentle, preservation-led process:

    1. Application of Algae Free chemical treatment to affected render surfaces.

    2. Dwell time allowed for organic growth to be neutralised.

    3. Super-heated steam cleaning used to remove algae and surface contamination without damaging the K-render.

    4. Final rinse and inspection to confirm uniform appearance.

    This method restored the render while maintaining its integrity.

    Boundary Wall – Surface Preparation

    The boundary wall was treated as a separate element due to the condition
    of the render:

    1. Identification of areas with severe render flaking and failure.

    2. Soda blasting used to remove loose and deteriorated render material in a controlled manner.

    3. Substrate left clean and stable, ready for subsequent re-rendering works by others.

    Soda blasting was selected to remove failed material without damaging the
    underlying structure.

    Site Access & Logistics

    Equipment
    • Super-heated steam cleaning systems
    • Soda blasting equipment
    • Cherry picker

    Chemicals
    • Algae Free – professional-grade algae removal treatment

    All methods and products were selected to suit residential rendered surfaces and preparation works.

    The Results
    • High-level beams and baffles cleaned, removing accumulated dust
    • Auditorium restored to a clean, fresh condition
    • Stage and backstage areas cleaned and presented to venue standards
    • Improved hygiene, air quality, and overall presentation
    • Works completed fully within the weekend programme