Private Mansion Roof & Skylight Cleaning – Harrow (July 2025)

In July 2025, we completed a specialist clean of a private mansion roof and skylights in Harrow. The roof featured very steep/sloped sides with clay roof tiles, requiring careful method selection and controlled work practices to achieve an even finish without damaging the surface.

The service combined:

• Steam cleaning for roof tiles and contaminated areas
• DDAC treatment to help reduce algae regrowth
• Pure water cleaning for skylight glass and frames for a spotless, streak-free finish

Project Overview

• Project type: Private mansion exterior roof & skylight clean
• Location: Harrow (UK)
• Time: July 2025
• Roof type: Sloped clay tile roof (very steep sides)
• Services delivered: Steam cleaning + DDAC treatment + pure water skylight cleaning
• Image folder: private-mansion-harrow-jul-2025

The Challenge

This project had three defining constraints:

1. Very steep roof pitches
   Sloped tile roofs need the right cleaning method and careful movement planning to maintain safety and avoid tile disturbance.
2. Biological growth on clay tiles
   Algae, lichen, and moss staining were visible across multiple sections, including around roof features and edges.
3. Skylights and rooflights needing clarity restored
   Skylight glass had visible dirt and contamination, and required a method that leaves no residue and no spotting.

Our Method

Steam cleaning for clay roof tiles

Steam provides effective removal of organic buildup and staining while being gentler than aggressive high-pressure approaches on delicate roof surfaces. We focused on consistent coverage across the tile runs and detailing around features.

DDAC treatment for algae prevention

After cleaning, we applied DDAC as a biocidal treatment to help inhibit algae regrowth and keep the roof looking cleaner for longer (maintenance frequency will still depend on shade, trees, and exposure).

Pure water cleaning for skylights and frames

For the skylights and rooflight glass, we used a pure water system to lift grime and leave a clear, streak-free finish. Frames and surrounding areas were also detailed to match the restored look.

Results

• Clay tiles restored with improved colour and a more uniform appearance
• Algae/lichen staining reduced across sloped roof sections and around roof features
• Skylight clarity restored, with clean frames and glass for a brighter finish from both outside and inside

What We Cleaned

• Sloped clay tile roof sections
• Flat roof areas around skylights/rooflights
• Skylight and rooflight glass + frames
• Localised areas of heavy organic growth (around roof details/edges)

Maintenance Note

Roofs in shaded or damp areas are more prone to algae return. A planned maintenance clean and periodic treatment can help keep clay tiles and skylights looking their best long-term.

FAQ

Steam vs pressure washing on clay tiles — why steam?

Clay tiles can be vulnerable to aggressive pressure, especially on older roofs or where pointing, flashings, or tile fixings are tired. Steam cleaning relies on heat with controlled flow to break down organic growth and grime, so we can clean effectively while reducing the chance of:

• lifting or cracking tiles
• forcing water under tiles
• stripping protective surface finish (where present)

If a pressure-based method is used at all, it should be carefully controlled and matched to the roof condition — but for many clay tile roofs, steam is the safer, more precise approach.

How long does DDAC treatment last?

DDAC is applied to help slow down algae regrowth, but longevity depends heavily on conditions. Typical factors that shorten lifespan include:

• shade from trees/buildings
• north-facing or persistently damp elevations
• nearby moss sources (gutters, overhanging vegetation)
• poor drainage or recurring runoff patterns

As a practical expectation, many roofs stay noticeably cleaner for months to a few years, with best results when combined with sensible maintenance (e.g., keeping gutters clear and scheduling periodic re-treatments where the environment is high-risk).