Guide
Soft wash vs pressure wash for a roof
The method matters more than the price. Here's why a high-pressure jet can do more damage than the moss.
Soft washing cleans a roof with a cleaning solution applied at low pressure. Pressure washing uses a high-pressure jet of water. On most roofs, soft methods are safer: a high-pressure jet can damage tiles, slates and ridge mortar and push water into the roof.
Munster Gutters, a Limerick roof and gutter company, warns against it: high-pressure washing can strip the surface off concrete tiles, crack older slates, drive water up under the laps and blast out ridge mortar (Munster Gutters). Ask any company how they clean before you agree.
The two methods
| Soft wash | Pressure wash | |
|---|---|---|
| How it cleans | A cleaning solution, applied at low pressure, kills moss, algae and lichen | A high-pressure jet of water strips growth off |
| Risk to tiles and slates | Low, when applied correctly | Can strip the surface of concrete tiles and crack older slates |
| Risk of leaks | Low | Can drive water up under the laps and into the roof space |
| Ridge and hip mortar | Left alone | Can be blasted out |
| Looks on the day | Thick moss may still need brushing off by hand | Clean straight away |
| Plants and run-off | The solution needs to be kept off plants | Lots of water and debris everywhere |
Pressure washing risks as described by Munster Gutters, a Limerick roof and gutter company, 4 July 2026.
Why pressure washing a roof is risky
Concrete roof tiles have a surface layer that helps them shed water. A high-pressure jet can strip it, leaving the tile less able to shed water. On older natural slates, the force can crack them. And because the jet is aimed at the roof, water is pushed up under the overlaps where it was never meant to go.
Munster Gutters puts it bluntly: "never let anyone clean your roof with a high-pressure washer" (Munster Gutters).
How soft washing works
The roof is sprayed at low pressure with a solution that kills moss, algae and lichen. Heavy moss is usually removed by hand first. The treatment then works on what's left. Ask the company what product they use, how they protect plants, ponds and paintwork, and how the roof should look on the day and in the weeks after.
Hand cleaning
For thick moss, most of the work is done by hand: scraping and brushing it off from the top down, bagging it, and clearing the gutters after. Munster Gutters describes its method this way: the bulk of the moss removed by hand with soft brushing and scraping, so the covering and mortar are not disturbed (Munster Gutters). Hand cleaning and a soft wash treatment are often used together.
Questions to ask before anyone goes up
- How will you clean my roof: by hand, soft wash, pressure, or a mix?
- What product will you use, and is it safe around my plants and pets?
- How will you protect the gutters, windows and paintwork?
- Will you clear the gutters at the end?
- What happens if you find a cracked tile or loose ridge?
- Is VAT in the price?
If a company offers to pressure wash your roof, ask why, and what they'll do to protect the tiles and the ridge. Then compare with a soft method.
Walls, drives and patios
Pressure washing has its place on hard surfaces like drives and patios. Render and painted walls usually suit a soft wash. The roof is the one place where high pressure causes the most harm.
Questions people ask
Is it OK to pressure wash a roof?
Munster Gutters, a Limerick roof and gutter company, warns against it: high-pressure washing can strip the surface off concrete tiles, crack older slates, drive water up under the laps and blast out ridge mortar (Munster Gutters). Ask any company how they clean before you agree.
What is soft washing a roof?
Cleaning the roof with a solution applied at low pressure that kills moss, algae and lichen. Heavy moss is usually removed by hand first.
Is soft washing safe for plants?
Only if the company protects them. Ask what product they use and how they'll keep it off plants, ponds and paintwork.
Which is cheaper?
It depends on the roof. Published Limerick prices for a full clean run from €450–€700 for a terraced house to €900–€1,500 for a 4-bed detached (Master Clean, VAT not stated).
Sources (2)
Prices and facts on this page were checked against these published pages. We are not connected to these businesses.
- Munster Gutters: munstergutters.ie
- Master Clean: masterclean.ie
Moss off the roof, price agreed first
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