A roof can be one of the dirtiest parts of anyone’s home. Let’s just think about this for a minute; it is a part of your property that is usually out of sight and even if it is seen, it is always at a distance. The area has nooks and crannies that will trap spores and soot, seeds and dirt; it will collect dust, dead leaves, bird droppings. The seeds might sprout, moss and lichen will grow and this will hold water on the area that should be shedding water. Anything landing on the roof that doesn’t lodge and take hold will roll down the slope and collect into the rainwater gutter, effectively blocking the free flow of rainwater and causing blockages and overflows. Roots from the sprouting vegetation will find its way under the slates or tiles and eventually snap the brittle roof covering and find its way into the roof space.
What to check when cleaning your roof
The obvious solution to this problem is to have your roof surface periodically cleaned to remove anything that shouldn’t be there and to keep your roof fit for purpose. While you are having the roof cleaned, whether it is by a contractor, handyman or as a DIY project, it will make sense to do the following little extra jobs:
- Clean out the guttering of any leaves, moss, twigs or soil.
- Guttering is in good order and all the joints are secure.
- Broken or loose slates and tiles. Have roofing contractors repair these at the same time or as soon as possible.
- Ridge tiles are secure and the pointing is still in one piece.
- Flashing around the chimney and have it repaired or replaced as soon as possible.
- Pointing on the chimney is in good condition and have it repaired when convenient.
- Chimney pot is secure and birds haven’t made their nests on it.
- Television antenna is connected to the chimney securely.
There are a few jobs here that will have to be pencilled into the diary for a later date, but don’t let them get in the way of cleaning the roof. You are only using it as an opportunity to get up near the roof to carry out the inspections for the more serious problems that may crop up.
The common problems
By far the commonest problem that you will find, is the growth of lichen and moss on roof tiles. It can look very attractive to have moss growing on the roof as it gives a sense of being rustic as well as one of age. Don’t be conned by the pretty moss growth, however, if roof moss removal is not done regularly, the roots of the vegetation will start to break down the surface of the tiles and cause them to crumble. The lifespan of the tiles will be seriously reduced and the moss will start to grow under the tile overlap forcing the two surfaces apart which will eventually cause the upper tile to snap.
How much does roof cleaning cost?
As always, the cost of getting things done around the house will vary because of a number of factors; roof cleaning is no exception. Any variation in costs will be caused by the following factors:
- Whereabouts in the country you live (London is the most expensive).
- The size of the company (Large companies have higher overheads than smaller ones).
- The size of your roof.
- Access difficulties to the roof.
- Poor state of repair?
- Large build up of moss and dirt?
- Style of roof?
- Most appropriate cleaning method.
The following average and indicative costs based on the size of cleaning company will be for a simple scrape clean using no specialist equipment or chemicals. The roof size is typically a standard four bedroom detached house. Hire of scaffolding will be extra as will the cost of chemicals used.
| Size of company | Roof Cleaning Cost |
| Small | £300 to £500 |
| Medium | £400 to £600 |
| Large | £450 to £850 |
How long does it take?
That depends on a number of factors:
- DIY or Contractor
- Size of roof
- Accessibility of roof
- Time of year
- Weather
- Scope of work
Is the work is being done by roof cleaning contractors or as a DIY project? If it is DIY, the time spent will depend on whether you know what you are doing, whether you are good with heights and how much spare time you have. A contractor wants to get on with the job and finish as soon as possible so his only holdup will be the weather. Wet or Cold weather will make the work take longer. After the scaffolding is in place, the actual work of cleaning the roof of a standard four bedroom detached will probably take about one day. Remember that afterwards, any mess must be cleaned and gutters washed before they can go any further. If the roof is to be treated preventing further moss growth, the roof tiles must dry out completely. This depends on whether it is dry and sunny. The tiles will take about one day to dry. After drying, the application of surface treatment will probably take about half a day per coat but will need to dry between coats.
Getting access to the roof
The amount of access you require will depend on the following factors:
- Are you are having your roof cleaned professionally or is it DIY?
- Are you going to do all the checks or it is just a cleaning job?
- How large is your roof area?
- How high are the eaves and guttering?
- How much cleaning will your roof require?
There are a few different access methods you can use depending on which of the factors takes precedence.
- Using a ladder standing on the ground and reaching up to the guttering height is useful for checking how dirty the roof and gutter actually are. They are not really suitable however for working from. Ladders need to be secured at the foot and at the top before anyone can safely climb one and it is only safe to do any work if there are at least three points of contact between the person and the ladder (2 feet & 1 hand, 1 foot & 2 hands, 2 feet & 2 hands), any other combination is unsafe. This leads one to the inescapable conclusion that it is only possible to safely work one-handed and with both feet on the ladder rungs.
- Cherry picker. This type of mobile access platform will make the job very easy. The operator is standing on a platform and surrounded by safety barriers. The platform can move vertically to the best available working height and the base unit can move as well. This is a good platform to work at gutter level. Some types of cherry picker have the working platform on the end of a hinged arm enabling the operator to move across the roof for better access.
- Full scaffolding. This will be a working platform running the full length of the house at guttering height. This allows easy reach to the gutter and a couple of metres up the roof slope. Depending on the amount of work needed on the roof it might be economically feasible to have an extension scaffold giving access to all parts of the roof up to ridge tile height.
- Tower scaffold. This is a working platform available from hire shops and assembled by the DIY worker. It only gives a working platform of about 1.5m x 1.5m but the whole tower stands on lockable wheels so it can be manoeuvred wherever the worker needs access.
- Roof ladders. These are special ladders designed to rest on the roof slope. The bottom is at the eaves, the ladder rests on purpose made padded feet resting on the roof tiles while the top is hooked over the ridge tiles. This allows anyone to walk safely up the roof slope. Access to the roof ladder can be from scaffolding or ladder.
Whichever one of these methods you choose will depend on the work involved. Removing moss from roof tiles will probably best be achieved using roof ladders and a tower scaffold (this will probably be the cheapest method as well).
We have now decided on the access method, what are we going to use to give us an efficient moss removal method?
Roof Moss removal
There are a few methods for roof cleaning contractors to get rid of moss on a roof.
- Scraper and brush. You need a paint scraper and a stiff bristle broom or hand brush (both would be better). You will need to be close to the moss to use the scaper, no matter where it is on the roof slope, so a roof ladder will be the best access method. A watering can or garden hosepipe will be a good idea to wash loose debris down the slope and into the gutters.
- Pressure washer. These handy machines are electrically powered and need to be connected to a garden hosepipe. They are also awkward to manhandle up a ladder and hold while spraying onto the roof. For this reason, it will be better to use a fixed scaffold platform that is near the ridge. Spray the pressurised water downwards over the roof so that the jet washes everything down the slope. It is also very important to ensure the spray is not pointed up-slope otherwise the water will be forced under the tiles and into the house. Although this is a good method to clean a roof, it will also be very messy with dirty water blown about all over the place. You will probably have to run the hose down the walls afterwards to clean up any muddy splashes. A big warning here is that pressure washers can strip the surface from tiles and also increase the likelihood of floods in the roof space.
Using chemicals to clean
Roof cleaning chemicals are available for DIY as well as trade use. One of the disadvantages of using a pressure washer is that it can very easily damage your existing roof tiles, creating more of a key for the moss to take hold and in extreme cases damage the tiles so they have to be replaced. Another option is to use a roof cleaner that kills any moss growing on the surface. This is applied to the surface using a pressurised hand sprayer. The biocide effectively kills any vegetation allowing the debris to be easily washed and brushed from the roof. An added bonus is that this biocide is useful for keeping driveways, footpaths and house walls clear of moss too. Once the moss has gone it is a simple job to seal and coat the tiles to prevent moss from gaining a hold on the surface again.
There are many chemicals that can keep roofs clear and the following prices will help you with calculating the roof cleaning cost of your house.
| Chemical | Size available | Price for 5L | Coverage | Uses |
| Moss Clear Pro | 5L or 25L | £35 | 100m2 per 5L diluted 1:5 | Moss, algae, lichen, mould, mildew and fungi remover. Use of driveways, roofs, patios, footpaths. Safe for children and pets when dry. |
| Roof Clean | 5L or 25L | £32 | 40m2 per 5L. diluted 1:1 | Black & white spot, algae, lichen, moss, surface grime. |
To conclude
Keeping your property looked after is very important if you need to maintain its value. Good maintenance means looking after every part of the house, including the roof. Regularly inspecting and cleaning the roof and guttering will not only increase their lifespan but also keep them looking good and will alert you to any problems that need repairs. As long as you are ok with working at height, it is feasible to maintain a roof as a DIY project, otherwise always get a professional roof cleaning contractor or roofer to come and do the work for you.
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