In the world of exterior cleaning just about anything can be cleaned by either pressure washing or soft washing.
The difference lies primarily in what we are cleaning and why although both can be used together depending on the situation.
Pressure washing is the use of high pressure water and soft washing uses chemicals.
Most of the time, cleaning stuff outside entails getting rid of organic growth such as moss, mold, algae, bacteria such as gloeocapsa magma (black streaks on roofs).
Especially in wetter and more humid climates all this stuff likes to grow on our homes and buildings and if not taken care of can lead to property damage as much of this stuff literally eats away at the exterior of your home.
Keeping stuff clean is important! And how you do it is important as well.
At a basic glance pressure washing is used to clean surfaces that are more solid such as concrete, metal, or other hard exterior surfaces.
Soft washing is used primarily for more delicate surfaces such as vinyl siding or asphalt shingle roofs (my industry). Often it is also used in conjunction with pressure washing because it loosens stuff up and makes it easier to blast off.
The trick is to get the job done as quickly and as efficiently as possible as often chemical can get expensive and why do more when less will do?
When to Pressure Wash
As mentioned pressure washing (or power washing) is best for hard surfaces.
Think concrete driveway, aggregate, metal roofs, decks, sidewalks and in some scenarios i’ve even seen tile roofs cleaned with it as well. Sometimes all we need is to blast off a bunch of shit with pressurized water.
If possible using some chemical can help speed things up. A good example is a driveway which you can clean with just a pressure washer but when you add bleach it makes the job go by much quicker and also helps keep the grime from building back up.
Standard practice is to wet the area down, apply chemical like sodium hypochlorite, let it do its job, and then get to work with your power washer.
When to Soft wash
Soft washing is my personal favorite because we can allow the chemical to the work for us, the most common being SH (bleach) as mentioned above. This is best for parts of the home that have a bit higher risk for damage such as the siding and the roof of the house which aren’t meant for any water other than low pressure.
Soft washing is incredibly good at killing organic materials and this makes it great for cleaning just about anything fast.
Take a house for example.
Here is a video of me spraying down the side of one of my clients home with a hand sprayer.
Soft washing is literally just spraying bleach and as you can see it happens almost instantly.
If I was to pressure wash this vinyl siding I might have blasted a bit too hard, wasted time, and maybe even caused slight damage to the home’s exterior.
This way I was also able to clean it safely and with much less water and not risk killing all the plants as can happen if you’re not careful with your spray.
Using cleaning solutions like chlorine or oxygen bleach can get the job done quicker and much cheaper.
This makes it especially useful for wood panel siding or asphalt shingle roofs which are notoriously tough to clean as the risk of damage can be very high.
My Roof Soft Washing method
Note: Never use a pressure washer to clean an asphalt shingle roof. Roofs are not designed for water being shot upwards so even with lower pressure make sure you are cleaning with a very gentle spray or shooting downwards.
Almost all roofs where I live have either moss or algae and the best cleaning method is hands down a soft wash. The results can be seen instantly, but it does sometimes take a few months for all the moss to fall off see how to remove roof moss for good.
My soft wash system is what’s called batch mixing in a 26 gallon water tank where I mix up my soft washing solution which is either a 2-4% SH mix or a 1/2 cup oxygen bleach to gallon mix.
Add a little surfactant to make bubbles (actually to hold the chemical on the job longer) and you’re good to start treating the roof.
The strength of your mix can vary based on whats growing up on the roof but generally you can see if the chemical is doing it’s job right away. I generally will use a lighter less “hot” mix as sometimes less is more and with stuff like moss you don’t really need a ton of harsh chemicals often you just need to blow off all the debris and any bulk moss, treat it and you’re good to go.
If you want to learn exactly how to clean roofs and gutters I have a short ebook all about this and I go much more into the process here
How to do this for clients/the best ways to hire a company to do this for you
Almost all pressure washing companies will offer soft washing. Its pretty standard practice and if you have questions ask them a little bit about their process as many are happy to explain it to you.
If you do this for clients glad you’re here doing some research! I still remember my first soft wash many years ago with a 2 gallon spray pump. That roof took forever but that simple bleach mixture made me $400 to spray a pretty easy roof so definitely learn what you’re doing and you can provide a great result and make some good money.
Generally most soft washing services vary on how much chemical you need to use as bleach in some areas can vary from $4-8 a gallon for the 12.5% stuff which is the highest you can usually buy.
Our average roof soft wash is an extra $2-300 on top of whatever else we did but I’ve seen some folks not charge less than $1,000 for getting up on the roof and spraying chemical.
Pressure washing prices tend to vary and around here many people charge between .10-30 cents a foot with some services like driveways being about $200-400.
Most power washers can handle a driveway but anything larger than that and you may need something bigger such as a 4 gpm machine or something.
Pressure washers are rated on how much water they use and how much pressure it creates.
Here as they say, more flow more dough and the more gallons per minute (gpm) the faster you will be able to clean. I personally just have a 2.5 gpm because I don’t really need it for the roofs and gutters we clean but it does come in handy for various driveways and sidewalks and such.
Conclusion
Really the key differences between soft and pressure is the level of water pressure and the amount of chemical used.
Make sure you do your research and use the best method for the situation at hand for whatever your desired results are.
There’s more than one way to skin a cat, so practice using both and you’ll be able to clean just about anything