How can you tell which roof in your street will probably need maintenance in a couple of years? Simple, decide which one has all the moss and algae growing all over it.
If you neglect your roof, you’ll find these plants will grow out of control. Their roots will find their way into weaknesses in the roof tiles and widen them until cracks appear.
You’ll have tiles or slates come loose, and eventually, you’ll replace them. These plants need water to survive, and when it rains, they’ll act like a sponge and hold as much water as they can. This then finds its way through the cracks into your roof where it damages the rafters and joists.
Now and again the moss will come loose and roll down the roof, ending up in the gutter. You’ll then have an overflowing rainwater gutter which saturates and damages the fascia boards
The average cost of cleaning a roof varies depending on a few different factors such as its size, what method you use for cleaning, and how easy it is to access the roof. In the UK a typical terraced 3 bedroom house costs between £5 and £12 per m2 for a clean only, while cleaning and sealing costs from £25 to £40 per m2.
You can avoid all this, just by regularly removing any moss buildup. And, you’ll have a good looking roof too. While the contractor is up there cleaning the roof, he or she might as well check on the state of your tiles and clean out the guttering too. Every little bit helps. Doesn’t it?
So, should we scrape the roof, use pressure washing equipment or roof tile cleaning products, or all of them?
How Much Does Roof Cleaning Cost?
There’s a lot of variation when it comes to roof cleaning. So, let’s break down a typical roof cleaning session into individual tasks and see how much each one costs.
Here is the full roof cleaning price list:
Assess the job
The roof cleaner needs to inspect the roof carefully. Is the roof made from tiles, slate or thatch, because you must deal with each one differently? Assess what’s growing there and the best way to dislodge the growth. While doing this see if there are any existing cracks in the tiles and if the mortar crumbles. Work out what access and safety equipment you need. And, do a risk assessment.
Roof Jet / Pressure Washing
Remove gutters and check for obvious broken tiles. Spray biocide to kill the moss. Then, use hot water and a high–pressure spray hose to dislodge the moss and wash the roof. Always spray from the ridge down to the eaves, never the other way around. This is because you mustn’t allow the jet to spray under the overlapping tiles. The spray may break the tiles and allow water into the loft. Afterwards, make any repairs as needed. Then allow the roof to dry followed by an application of tile sealant.
Cleaning the roof tiles using a jet washer will cost anything from £600 to £1100, and will take about 1 to 2 days depending on roof size and the number of repairs.
Just Moss Removal
If you don’t want the roof washed, and instead just want the moss cleaned from the roof, you can use a scaper and long-handled broom to remove the vegetation. First, spray the biocide. Then, scrape off all the moss followed by a thorough brushing to remove all dirt. Inspect the roof for damage and repair as needed. Clean the gutters and downpipe. Then, you can add a coat of tile sealer to help prevent regrowth. Price for this will range from £600 to £1500 and will take about 2 or 3 days depending on roof size and the number of repairs.
Apply roof sealant and colour
Only apply sealant and colour on a clean roof after jet washing.
Allow tiles to dry thoroughly and brush any dust from the roof. Apply coloured or translucent seal to the edges of the roof. Do this by hand to reduce spillage and waste. Then use a spray to apply the sealer to the other tiles. Allow sealer to dry, followed by a second coat.
The price to have a jet wash and sealer application will cost anything from £1200 to £2500 minimum depending on roof size. The sealant will take about a day to do, on top of the cleaning work already described.
Clean entire roof
Although you can use a broom to dislodge the moss, using a high-pressure hose is much easier. Remember that working at height isn’t easy and you must always wear a harness and safety line to prevent falling. Walk along the ridge tiles to start, and apply a biocide treatment to the moss. Work your way down the slope as you go. After the moss dies, remove it from the top to the bottom. After cleaning the entire roof, you can help prevent it from coming back by applying a coat of sealer.
If you have a slate roof rather than tile, be careful. Slate is much more fragile and will easily break if the water pressure is too high.
If you have a thatch roof, don’t use water at all. Instead, shave off a few millimetres from the straw and the vegetation will go too.
Conservatory roof cleaning
Conservatory roofs need cleaning just like any other. Generally, the pitch is shallower so there’s more chance of dirt collecting. However, because a conservatory roof is usually made from plastic or glass, there are fewer places for the moss to take hold. Use the same methods as for a tile roof. And, don’t forget to spray from the top downwards to prevent water from getting under the lead flashing and elsewhere. If you intend using a sealer on this, make sure it’s compatible with the conservatory roof material and that it’s translucent.
All working at height requires an access platform, ladder and safety harness. Make sure you know how to use them. You’ll also be washing dirt, vegetation and copious amounts of water from the roof. So, make sure you protect the ground around the perimeter of the house. Place enough plastic sheets to collect all the solids.
Factors to Consider
We’ve already hinted at other factors that affect a roof cleaning job. So, let’s have a quick look at these.
- Size of house and size of the roof.
- The number of repairs needed.
- How much vegetation is growing on the roof?
- Type of roof.
- Accessibility of the roof.
- Height of the roof.
And of course, a hand clean will take much longer than using a jet washer. You’ll also have to take into account the time of year, as winter months have shorter daylight hours and more chance of rain. Don’t forget, prices in London and surrounding counties are generally more expensive than elsewhere in the country. Usually at least 20% more.
There will probably be many moss removal companies in your area. The smaller ones usually charge less than the larger companies because they have fewer overheads. Don’t dismiss the small company or single tradesman out of hand. They often take more care over their work and aren’t always rushing off to do the next job.
How Roofs Are Cleaned: Step-by-Step
You might not know what happens when the contractor cleans your roof, so let’s run through the steps and see what your money buys.
- Inspect the job from the ground and do a risk assessment to identify the risks and how to reduce them. Determine what access equipment to hire, and what tools you need.
- Erect the scaffolding paying attention to protecting the roof edge.
- Cover the ground with tarpaulins to protect the garden.
- Disconnect the gutters from brackets and downpipes.
- Check the roof for obviously broken tiles and replace.
- Confirm the cement areas are in good condition.
- Treat roof with a biocide and allow to dry.
- Clean the roof with a power washer and scrapers.
- Clean gutters and replace.
- Make any cement repairs where needed.
- Apply sealant to roof tiles. This can be coloured or translucent.
- Clean fascia boards, soffits, gutters.
- Remove access platform.
- Clean up the area and put away tarpaulins.
- Dispose of waste material.
- Supply guarantee and submit an invoice.
Avoiding Bad Tradesmen
Unfortunately, many rogue tradesmen do this kind of work. They reckon it’s easy money and doesn’t require a lot of skill. How wrong can they be?
Most cowboys don’t have formal training and take risks that can easily be avoided if they only knew what they were doing. If someone doesn’t know the procedures inside out, you could end up paying over the odds for a shoddy job. In fact, it’s quite common for them to take your money upfront and disappear without doing any work.
How do you avoid these disreputable guys? There are certain things you should look out for.
- Avoid quotes that are too low. Although we want to save money, you must understand that you get what you pay for.
- Check out the company online. Then, look at the reviews and build up a picture of the company.
- Many reputable trades sites supply online quotes. You’re reading one right now. These sites only deal with experienced professionals who supply insurance and qualification certificates.
- Ask neighbours and friends if they can recommend anyone or if they know of anyone who’s recently had their roof cleaned. Why not drive by the house and look at the roof?
Roof Cleaning Cost FAQ
Is it safe to power wash a roof?
That depends on the type of roof you have. Slate roofs are more fragile than tiles and might become dislodged with the force of the jet. Just turn the pressure down before you wash these.
Can moss on roof cause leaks or damage?
Definitely. As moss grows, it thickens and will lift slates and tiles. Eventually, the slate cracks or cement crumbles allowing rain to get inside.
How do I clean the roof myself?
Only attempt this if you are happy to walk on your roof. Always wear a safety harness and above all, know what you are doing. Cleaning a roof should be within the skills of a fairly good DIY enthusiast. So, as long as you take it slowly and don’t mind heights, you should be okay.
Will bleach damage roof shingles?
The occasional cleaning won’t do too much damage. However, if you repeat it regularly using harsh chemicals like bleach, you’ll damage shingles and shorten their life.
Does vinegar kill moss on roofs?
Yes, it does. Vinegar is a weak acid, and just like acid rain, it’ll kill the vegetation it lands on. Then, the moss will be easy to scape off the roof. However, make sure you protect the plants on the ground from any splashes by using plastic sheets.
Get Roof Cleaning Quotes
Cleaning your roof will give your home a new lease of life and make it look like new. You can get a better understanding of how much roof cleaning costs near you by filling out the form at the top of the page. You will receive 3-4 quotes from reputable companies for free.