Over the years, roofs accumulate moss and dirt. One technique used to thoroughly remove the moss is high pressure water. This can divide opinion.When asked ‘Is it safe to pressure wash a roof?’ many people would answer ‘ NO’ …. Why is this?
They may have had the experience of irresponsible contractors doing a bad job. Or possibly read negative reviews on the internet. Some of these reviews are not without reason- There are potential drawbacks to weigh up when considering this service…
The last thing any homeowner wants is water getting into the roofspace ( this is under the roof tiles but above the house ceiling). So jetting a large volume of water with concentrated flow at high pressure would be risky on roofs which already have damp problems or leaks. If the roof is in good condition then water ingress will not occur as all the water will run off straight into the gutters.
Another concern may be that high pressure water can damage the roof tiles. Any tiles that are already broken or loose may be dislodged with the high water flow. Any loose pointing will also likely be washed out and down the roof. This should be made clear by the contractor to the client when quoting the job. Conversely we find after the Roof is clean and clear of debris, this is a perfect time for maintenance to be done.
What about the integrity of the tile? Can pressure washing weaken or shorten the lifespan of the roof?
The most common roof tile material is concrete. So most concrete tiles that are in average condition would easily withstand a high pressure clean. It’s important to note the contractor should use the correct technique and equipment. The nozzle at the jet end should be like a sharp knife slicing the moss off rather than a blunt hammer bashing it up. Concrete tiles can sometimes have a granular coating which does in time naturally weather away. Often this has already worn off before the need to clean has arisen. Other common materials are clay and slate. Clay tiles are easy to wash down, whereas slate can be thin and would need very gentle cleaning. But as they are less porous and have a smooth surface they do not hold moss like concrete does.
‘ Is it safe to pressure wash a roof?’ It can be totally safe yes. We would assess each roof on its own merit. We can produce fantastic results , dramatically improving the buildings aesthetic . Removing moss can help with free flowing water drainage. Pressure washing is the best way to remove moss and dirt from between each joint, and rinse through gulleys and gutters.
Heres the great thing about our service….once it’s clean, you won’t need to pressure wash a roof again. We treat the tiles with biocide that inhibits biological growth. Repeating this annually keeps the Roof sterile ,therefore clean for good.
When roofs are unsuitable for pressure washing we have other methods….
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