Site survey & substrate assessment
Stone and mortar identified, soiling type confirmed (biological / atmospheric / paint), test patch agreed with conservation officer or heritage consultant.
DOFF cleaning — heritage-grade superheated steam
Conservation-grade superheated steam cleaning for heritage stone, listed buildings and delicate masonry — recommended by Historic England.
What is DOFF cleaning?
DOFF cleaning is a low-pressure superheated-steam cleaning system developed for sensitive heritage stone and masonry. Water is heated to approximately 150°C and delivered at low pressure (around 5 bar) to remove biological growth, paint, atmospheric soiling, lichen, moss, chewing gum and most weathering deposits — without damaging the underlying substrate. The method is recommended by Historic England and English Heritage for use on listed buildings, cathedrals, war memorials, statues, lime-mortared masonry and other delicate substrates where pressure washing or chemical stripping would cause damage. Apex delivers DOFF cleaning via IRATA-certified rope access teams — combining the conservation-grade technique with the access method that keeps the surrounding fabric, scaffold-free.
Part of Rope Access Division.
How we deliver.
DOFF / ThermaTech / TORC selection
Method matched to the substrate and the soiling: DOFF for general superheated steam; ThermaTech where higher pressure is permissible; TORC where micro-abrasive precision is needed for stubborn paint or carbon deposits.
Rope access delivery
IRATA-certified teams deliver the cleaning entirely on rope — no scaffold, no MEWP, no platform footprint. Suitable for cathedral towers, spires, chimneys, statuary, and any heritage elevation where ground-up access is impractical.
Biological & atmospheric soiling removal
Removes biological growth (lichen, moss, algae), atmospheric pollutant staining, traffic-film carbon, and most paint coatings — without damaging lime mortar or original stonework.
Conservation-officer sign-off
Test patches and method statement documented to the standard expected by conservation officers, listed building consent and faculty jurisdiction. Photographic records before/during/after.
Aftercare & monitoring
Optional follow-up monitoring to track biological re-growth, soiling return rate and substrate condition. Combined with biocide treatment where appropriate to extend the cleaned interval.
Where we deliver.
DOFF cleaning is the go-to method anywhere conventional pressure washing or chemical strippers would damage the underlying fabric — heritage, listed and conservation-area buildings across the UK.
- Cathedrals & churches
- Grade I & II listed buildings
- Statues, monuments & war memorials
- Heritage stone facades
- Conservation-area commercial
- Universities & colleges
- Country houses & estates
Case studies.
See moreRevolut HQ, Canary Wharf
Two 5m flex face letters installed at Revolut's global HQ — heavy-lift sections in excess of 900kg, mixed BMU and rope access.
Read moreLeonardo Hotels Re-Brand
Nationwide signage rollout converting the Jurys Inn estate to Leonardo Hotels — flex face, built-up and totem signage across the portfolio.
Read moreWalcott Hall, Stamford
Restoration of original timber sash windows on a Grade I listed hall, delivered while the building continued to host events.
Read moreHyatt Place, Leeds
Four sets of illuminated built-up lettering installed during the live construction phase, with bespoke temporary anchorage.
Read moreTrue Student
Multi-site brand rollout across student accommodation buildings — built-up signage, contra-vision vinyl and large-format banners.
Read moreStaycity Aparthotels, London Heathrow
Two 7.5m illuminated tray signs installed adjacent to live railway infrastructure, delivered in coordination with Network Rail.
Read moreFAQs.
What is DOFF cleaning?
DOFF cleaning is a low-pressure, superheated-steam system that heats water to approximately 150°C and delivers it at low pressure to clean delicate stone, masonry and listed buildings. It removes biological growth, paint, atmospheric soiling, lichen and chewing gum without damaging lime mortar or original stone — making it the conservation method of choice for heritage fabric.
Is DOFF cleaning safe for listed buildings?
Yes — DOFF is the cleaning method recommended by Historic England and English Heritage for listed and conservation-area buildings. Its low pressure means there's no scouring of the substrate; the high temperature kills biological growth at the root rather than just removing the surface. We agree test patches and method statements with the conservation officer or faculty jurisdiction before bulk works begin.
What's the difference between DOFF, ThermaTech and TORC?
DOFF is the original superheated-steam system (around 150°C at low pressure) — best for biological growth, paint and general soiling. ThermaTech operates at slightly higher pressure for tougher deposits where the substrate can tolerate it. TORC adds a micro-abrasive component (very fine dolomite) for stubborn carbon deposits and tough paint layers. All three are made by Stonehealth and are used in combination depending on the substrate and soiling.
How much does DOFF cleaning cost?
DOFF cleaning is typically quoted per square metre, with rates depending on the soiling type, substrate, access method and the conservation requirements. Rope-access DOFF (no scaffold) is usually substantially cheaper than scaffold-erected DOFF. Get in touch via the contact form for a free site survey and fixed quotation.
Will DOFF cleaning damage lime mortar?
No — DOFF was developed specifically to clean fragile lime-mortared masonry safely. The low pressure (around 5 bar) means there's no erosion of the mortar joint, and the high temperature sterilises rather than blasts. Test patches are always agreed with the conservation officer before bulk works.
How long does a typical DOFF cleaning project take?
Project duration depends on the area, the access method and the soiling severity. As a rough guide: a typical heritage facade clean might take 5-15 working days on rope. We provide a programme with the quotation so you can plan around scaffold-free works.
Talk to our Rope Access team about doff cleaning
Contact our Rope Access team today about your project. We aim to respond within 24 hours.