What is the best way to clean a roof ? Pressure washing or Soft washing

Before & After Soft Wash

How to clean a roof safely and effectively

There is a great deal of discussion online on the best way to clean roof tiles that is effective and will NOT damage your roof. Gleam Team Cleaning Services are professional exterior cleaners specialising in roof moss removal and soft washing roofs in Kent, London and the south east including Surrey and Sussex.

This article relates to our experience of removing moss, algae and dirt from tiled roofs combined with other expert sources. A professionally cleaned roof can dramatically improve the appearance of a house or commercial building by restoring it to its natural colour. Customers, their neighbours and even passers by often remark that it looks like a new roof.

Roof after soft wash cleaning

If left untreated roofs can aquire a thick carpet of moss, algae, lichen spots and dirt making a roof look old and unkept. What looks like dirt is very often actually black algae staining that has colonised the roof or perhaps just one side of it. Moss and algae thrive in dark and damp conditions so areas that get little sunlight or are shaded by overhanging trees or other buildings tend to be the worst affected areas.

However, after removing moss the tiles can easily be cleaned at low pressure using the correct specialist soft washing cleaning products and an anti fungicide or biocide will prevent moss and algae returning for at least 1 year and almost certainly considerably longer. The product we use remains effective for several years in our experience.

Is moss damaging to roofs?

If you spend any time researching the subject of moss and its effect on roof tiles you will find conflicting advice and opinions. Unsurprisingly, companies providing roof cleaning services will say that moss can be harmful and damaging to roofs while another website will dismiss this claim. However, most reputable and independent roofing experts agree that moss should be removed to maintain a roof and prolong its life.

Roofing Megastore state very clearly

“moss growth can severely compromise your roof”

The damaging effects of roof moss can include:

  • breaking tiles and causing cracks as it grows and expands
  • broken tiles lead to leaks in your roof
  • retains moisture which can have a degrading effect on roof structure when absorbed by the tiles
  • wear down the protective coating on tiles
  • grow into mortar joints holding ridge tiles which breaks up the joint and loosens tiles
  • add significant weight to a roof
  • block guttering and downpipes
  • cause mess on your driveway and patio when it blows off

Is roof cleaning necessary?

Roof tile manufacturers Marley say that excessive moss can affect the flow of water down a roof and hampers drainage and moisture retention can lead to damage and leaks. They recommend removing excessive amounts of organic growth, moss and lichens to avoid the possibility of water entering the loft space. One of the recommended methods of moss removal is scraping ( from-my-roof).

Is it safe to pressure wash roofs?

Marley are one of the UK’s leading tile manufacturers and they clearly state on this maintenance page of their website:

“The use of high powered jet washes is not recommended as it can damage the surface of the slate or tile, thus reducing its expected life considerably.”

Other tile manufacturers all agree on this and specifically warn against pressure washing roofs and they are the people who should know. No one knows their products better than the manufacturers and that is why Gleam Team do not pressure wash roofs. There are other good reasons to avoid blasting roofs at high pressure such as:

  • the horrendous mess that would be made all over the customer’s and neighbouring properties from power washing at height. In windy conditions the moss and dirt would fly even further
  • likelihood of damaging and dislodging tiles
  • damage caused from walking on the roof
  • risk of water entering the loft
  • additional costs incurred from hiring expensive cherry pickers
  • pressure washing only removes surface dirt and does not kill or remove algae and lichen spores below the surface. this means they will soon recolonise the roof making it look dirty again with black staining

Is soft washing a roof safe?

In a word YES. Of course it should be done by an experienced soft washing company who use safe, approved soft washing cleaning products but when it is done properly it is completely safe to clean a roof using softwashing.

What is soft washing a roof ?

It is the low pressure application of specialist outdoor cleaning products to safely clean and remove black, green and red algae, lichen, moss, other biological spores and dirt. It was developed as a way to clean fragile materials that are likely to be damaged by power washing.

Soft washing is particularly suitable for cleaning:

All of these surfaces are susceptible to damage from blasting with powerful jets of water. Soft wash chemicals are applied at a gentle low pressure from extendable water fed poles that are also used by window cleaners. The product is sprayed onto the surface through a brush head or nozzle and gently agitated. The long reach poles are excellent at reaching areas difficult to access such as the top of roofs, guttering and walls.

The cleaning products we use are specifically developed to clean away the black algae covering roof tiles. After they have had time to take effect they are simply rinsed off with clean water and the process is repeated if necessary to achieve a dazzling and thorough clean making roofs and exterior walls of your home look like new again.

Another benefit of soft wash cleaners are that they will keep your roof cleaner for longer. This is because algae spores are automatically absorbed into porous materials like roof tiles and pressure washing alone cannot clean them. However, soft wash biocides are also partly absorbed into the tile killing all the invisible spores below the surface and preventing them recolonising the tiles. A jet washed surface will only clean the outside area meaning algae spores will start to spread again after cleaning and it will soon look dirty again.

After softwashing we apply a highly effective long lasting anti fungicide to keep your roof clean and free of moss for a long time to come.

OUR MOSS-FREE GUARANTEE TO YOU – if moss starts to grow again on your roof within 12 months of our cleaning it, we will come back and treat it again free of charge

What is the best way to clean a roof? Soft washing vs Power washing

Based on the above information Gleam Team Cleaning Services believe that the best, safest and most effective way to clean roofs is by using low pressure soft washing methods.

  • it will not damage roof tiles
  • it is a more thorough and effective clean
  • more cost effective
  • longer lasting
  • it is cleaner, tidier and less inconvenience to you and your neighbours

How do we clean roofs in Kent, London & South East

We first lay tarpulin around the house to catch falling moss and cover downpipes to stop bloackages.

We access the bottom of the roof, above the guttering, using ladders or a scaffold tower and then use extendable aluminium poles with a scraping tool attached to manually remove the moss. Gutters are cleared and emptied on completion and during the process.

After removing the moss we soft wash the roof using water fed poles and rinse it clean. We then apply the moss inhibiting anti fungicide.

Roof cleaning cost in UK

Prices to clean a roof vary depending on the extent of the cleaning and size of the property. Moss removal only will be cheaper than a full soft wash or pressure washing. According to roof pressure washing prices average between £8 to £15 per square metre. There are also significant regional price variations with the usual higher prices in London and the south east.

Ease of access to the roof is another factor that can affect costs as this can require equipment hire and be more labour intensive for difficult to reach areas.

Gleam Team moss removal and roof cleaning prices start at £300 and increase with the size of the roof. Our service includes manual moss removal followed by a full soft wash cleaning of the tiles and moss inhibiting treatment. Typical prices are as follows:

  • Terrace house = £300-£500
  • Semi detached = £500-£700
  • 3/4 Bed Detached = £700+
  • These roof cleaning costs remain the same for all areas we operate in. So our roof cleaning service in London is the same price as it is in Kent and across the south east
  • The moss-free guarantee applies to all prices

Gleam Team are based in Maidstone and our roof cleaning service is avaialble throughout Kent including Sittingbourne, Tonbridge, Sevenoaks, Tunbridge Wells, Wrotham, Meopham, Dartford, Ashford and Canterbury.

We also cover Bexleyheath, Sidcup, south London, Surrey and Sussex. Please call 07581 681994 or email using the contact form for a free no obligation quote.

We now offer our roof cleaning service in Essex.

We also specialise in cleaning brick walls, render, house and building exteriors and block paving, driveway and patio cleaning and sealing.

References used – . February 2020

Share this post