Pressure washing a roof can be done without damaging the shingles by using a PSI lower than 1500, a 40-degree nozzle, and a pressure washer detergent. Cleaning the roof with a pressure washer should start at the highest point and end near the access point, in order to avoid slipping on wet tiles. The pressure of the unit should be tested on a small area and adjusted on the way. The safe way to pressure wash a roof is to divide the area into small sections and power clean them one at a time. Pointing the nozzle under the tiles and stepping on shingles that have mold, moss, or algae should be avoided.
How to pressure wash a roof is discussed in detail below.
Is It Safe to Pressure Wash a Roof?
Most people that you ask will probably tell you that it isn’t. And technically speaking, their answer is not wrong. Granted, pressure washers are known to get the dirt out of concrete, but they might not be as efficient in asphalt – not the shingle-sized options anyway.
Asphalt shingles – and most types of shingles used in your roof – are quite thin. They also have a protective coating that protects your home from the weather – and even then, it might be damaged. Think about what would happen if you were suddenly hit by a great hailstorm. In most cases, it would end up damaging your roof, wouldn’t it?
Now, think about the average power of a pressure washer. It is quite strong and can cause a lot more damage. Not to mention that it comes from a smaller distance. It will simply strip away your roof’s protective coat and do more damage than good.
Here, we should also mention that the pressure washer must be set on a flat surface – and as we know, roofs are anything but flat. Pressure washers can have a bit of a kickback when they are started, which can put the user at risk. You can also slip on the tiles if you are not careful enough. Unless you are a professional with the right tools, you might be placing yourself in danger.
Is There Still a Way Around It?
We did say that it’s difficult and not exactly recommended – but at the same time, it is not entirely impossible. You need to prepare yourself for the risks, and also use the right tools and attachments.
One can’t help it, if your roof is packed with lichen and algae, you have to clean it. That being said, the only recommended method is soft washing. This involves using a unit with very low pressure, along with nozzles that can spread out the pressure. White and black nozzles are generally the most recommended kind.
Aside from using the correct pressure washer, you must also be careful where you step. Make sure not to step on the wet shingles, and particularly not on wet algae. If you are not confident enough that you can do it yourself, then you might want to ask a professional to help you out here. They will know precisely how to move with this delicate task.
How to Pressure Wash a Roof
Washing your roof with a pressure washer needs to be done with the utmost care. If you are confident that you can do it and you have purchased a low-pressure unit, then you may proceed with the following steps:
1. Cover the Sensitive Areas
Do you have any plants or sensitive areas around the house? In that case, you might want to cover them. If you’re thinking that “rain does not affect them, why would dropping water do so,” think about the detergents that are usually used with your pressure washer? You don’t want that falling down your plants, so cover them with some tarp.
2. Attach the Correct Tip
The power coming from your portable pressure washer may deal quite some damage to your pressure washer, which is why you need to choose the correct spray tip. Generally, a 40-degree or wider is appropriate for washing your roof, as it will not damage the shingles.
3. Spray the Solution
Stand on a dry surface of the roof and point your pressure washer downward. You need to make sure you won’t slip from the roof. Ideally, you should get a portable pressure washer, as it has less kickback.
Wet the roof with the lowest setting of the pressure washer, and then spray pressure washer roof cleaner on it. Brigs & Stratton has some great detergent that you can use for your house, and many professionals recommend it. This will kill the algae on the roof and leave it clean. Leave the solution there for a short time, allowing it to do its work.
4. Wash It Off
Once it sat for enough time, you may wash the detergent off the roof. Start from the top down, using the pressure washer at its lowest pressure. Cover a couple of shingles at a time, and make sure not to pressure wash the same area for too long. It may damage the shingles. You should also not spray any water upwards, as it can push under your shingles, tearing them down.
5. Inspect the Roof
Each time, after pressure-washing your roof, you may want to inspect it for any potential damage. You should always keep your third eye open as you are doing the work but make a proper assessment at the end as well.
Moreover, make sure not to over-wash your roof; just do it when it looks like it’s absolutely necessary. If you wash your roof with a pressure unit too often – no matter if you are using low pressure – you risk wearing the shingles down.
The roof is a delicate part of the home, which is why you need to be particularly careful when you are cleaning it. For safety reasons, you might want to contact a professional before washing the roof. However, if you follow these steps thoroughly, you might be able to do it as well.