Is DOFF safe for limestone and soft brick?

Yes, when a test patch confirms no surface disruption. The low pressure and controlled heat avoid the gouging that high-pressure jets cause. We run the trial at the start of every job and only go ahead if the substrate reacts well.

Does DOFF cleaning strip paint?

It can. That is why the regime is matched to the substrate. On facades where the paint or coating must stay, we verify on a trial area first and adjust the regime to keep wanted coatings in place.

How is run-off managed on a DOFF job?

All run-off is contained, captured and disposed of under a project-specific RAMS. Part of the survey is a drainage check and a chemical-handling plan. That keeps the clean compliant with site and environmental requirements.

Can A Star use DOFF at height?

Yes. We access high facades with MEWPs or traditional scaffold, chosen at the survey. The DOFF lance gives good reach and low recoil, which supports controlled work at height.

What preparation is needed before DOFF cleaning starts?

We carry out a substrate test, agree any chemical use, confirm the run-off plan and coordinate access. No preparatory work is needed from the client beyond isolating sensitive services and providing clear access.

Insights · specialist cleaning

What is DOFF cleaning, and when is it the right system?

Tomas Nejedly, Managing Director · 10 June 2026

DOFF is a superheated steam cleaning system that lifts soiling from masonry, stone, brick and heritage facades without high pressure. The steam reaches around 150°C at the nozzle but operates at low pressure, so it removes biological growth and soiling without the surface erosion high-pressure jets cause. A test patch precedes any full run.

How does DOFF cleaning work?

Per Stonehealth, the system manufacturer, a DOFF unit heats water to produce superheated steam at roughly 150°C at the gun and discharges it at low pressure, comparable to a boiling kettle. The high temperature softens and dislodges organic matter, paint residues and general soiling. Because the pressure is so low, the substrate surface stays intact. Trained operatives and a careful test area confirm the settings before the main clean.

Is DOFF safe for listed and heritage buildings?

The manufacturer reports the DOFF system is widely specified for listed and heritage buildings. The low-pressure steam does not abrade soft stone or open surface fissures the way high-pressure washing can. Every project is different, and conservation approvals remain project-specific. We run a small trial patch and, if any chemistry is needed, agree the specification before touching the wider fabric.

How is DOFF different from pressure washing and chemical cleaning?

Aspect	DOFF superheated steam	Pressure washing	Chemical cleaning
Pressure	Low at the surface, per the system manufacturer	High, cold water jets	Low to none; applied by spray or brush
Temperature	Around 150°C at the nozzle, per the system manufacturer	Cold water, no heat	Ambient
Substrate risk	Very low when correctly operated	High on soft stone and mortar	Depends on the chemistry; etching and staining possible
Heritage suitability	Widely used on listed buildings, per the system manufacturer	Rarely specified on historic fabric	Possible with careful specification and conservation approval
Biological kill	Effective; heat kills moss, algae and spores	Mechanical removal only; no thermal kill unless hot-water units are used	Effective through biocides
Water use	Moderate; mostly steam that condenses	High volumes	Variable; includes rinse water

When DOFF is the wrong choice

DOFF is not a one-system-fits-all answer. If the surface is friable and a trial patch shows spalling or rapid moisture uptake, we do not proceed. Thick, bonded encrustations that need mechanical force are better tackled with other methods first; DOFF can then finish the clean. If an existing paint layer must stay but is already failing, steam may lift it faster than intended, so we specify the method to match the condition. And where run-off containment is impossible and site drainage cannot accept any discharge, a dry method becomes necessary.

Frequently asked questions

Is DOFF safe for limestone and soft brick?: Yes, when a test patch confirms no surface disruption. The low pressure and controlled heat avoid the gouging that high-pressure jets cause. We run the trial at the start of every job and only go ahead if the substrate reacts well.
Does DOFF cleaning strip paint?: It can. That is why the regime is matched to the substrate. On facades where the paint or coating must stay, we verify on a trial area first and adjust the regime to keep wanted coatings in place.
How is run-off managed on a DOFF job?: All run-off is contained, captured and disposed of under a project-specific RAMS. Part of the survey is a drainage check and a chemical-handling plan. That keeps the clean compliant with site and environmental requirements.
Can A Star use DOFF at height?: Yes. We access high facades with MEWPs or traditional scaffold, chosen at the survey. The DOFF lance gives good reach and low recoil, which supports controlled work at height.
What preparation is needed before DOFF cleaning starts?: We carry out a substrate test, agree any chemical use, confirm the run-off plan and coordinate access. No preparatory work is needed from the client beyond isolating sensitive services and providing clear access.

For a site survey and a substrate-matched cleaning specification, start at our DOFF and jet washing page.