If you’re a house owner in the US, you have some concrete surface on your property. Most likely a driveway, but also perhaps a wall or a pathway. Whatever the surface may be, it will get dirty over time. That‘s when your power washer comes in handy.
- General Recommendations for Pressure Washing Concrete
- What Types of Concrete Are There?
- How often Should I Pressure Wash Concrete?
- When Should I Pressure Wash Concrete?
- What Tip Should I Use for Pressure Washing Concrete?
- What Pressure Setting Should I Use for Concrete?
- What Products Should I Use for Concrete?
- How to Pressure Wash Concrete
With a pressure washer, cleaning concrete surfaces is as easy as counting 1,2,3, if you know what you’re doing.
Pressure washing concrete is also highly advisable, as there’s no better way to clear both its surface and pores. But how do you go about it?
Worry not, because whether you’re a seasoned pressure washer pro or are yet to hold one in your hand, this article will cover the topic of pressure washing concrete wall to wall and offer valuable tips for pressure washer enthusiasts of all levels.
General Recommendations for Pressure Washing Concrete
Before moving to the “how to”, we must first cover the basics of concrete maintenance and some general advice for pressure washer use specific to concrete surfaces.
We will cover what types of concrete you may encounter and how to treat them, how often should concrete be pressure washed, a general overview of products you should consider for concrete maintenance (not brand specific, we’re an independent production), pressure washer tip choice for concrete and recommended pressure range that can be safely applied to concrete surfaces.
What Types of Concrete Are There?
Most concrete is made of 3 basic ingredients: cement, sand and construction aggregate. However, not all concrete is the same and some distinctions should be made. Different types of concrete have different properties, including hardness and porosity.
Although your typical driveway usually uses the classic 1:2:4 ratio of the aforementioned ingredients, alternatives are very common and may require some adjustments to your typical concrete pressure washing routine.
What follows is a redacted list (opens in a new tab) of “concrete type” materials you may encounter in your daily life and on your property.
1:2:4 concrete (or simply “concrete”) will be our base material throughout this article. Its formula consists of cement, sand and construction aggregate in a 1:2:4 ratio. Concrete can be either mixed on site or precast into blocks and then assembled.
Therefore, concrete blocks should be treated just as concrete, with an additional consideration of the block’s edges, which are more prone to be chipped off by an e.g., 0° nozzle.
You may also find it harder to clean out all the crevices between concrete blocks. In such a case, it is advisable to rub your detergent in with a utility brush.
Ready-mix concrete (opens in a new tab) is pretty much just concrete that is premixed. It can be safely treated as 1:2:4 concrete.
Pre-Stressed Concrete and Reinforced Concrete
Beware! Concrete may be pre-stressed or reinforced (opens in a new tab) when used in walls, which refers to adding steel components to its core.
However, the procedure only changes the properties of the interior of the material. The surface, which is the part you’ll be pressure washing, still has the properties of plain old concrete. The take-home message is that reinforced concrete does not give you leeway to apply any additional pressure by your pressure washer.
Glass concrete (opens in a new tab) follows a similar formula to concrete, but adds recycled glass shards to the mix to make it a tad bit fancy.
This results in a decorative material used in facades and indoor flooring, but also construction blocks used in garden pathways which go quite well with art deco house design or around swimming pools.
Note that the shards, while strong, are still as brittle as any other glass and therefore, low angle tips must be avoided. Spot cleaning should only be done by hand.
Lime concrete (opens in a new tab) (also known as limecrete) is made by replacing the cement in concrete with lime. It is widely used in surfaces that are artificially heated, but is also used as an environmentally friendly or decorative substitute to concrete.
However, limecrete has its downsides, as it is more porous and therefore, less durable and easily damaged by high pressure (e.g., by low angle fan nozzles). Care should also be taken when choosing detergents and care products, such as sealants, which may impact the material’s porosity.
Asphalt concrete (opens in a new tab), sometimes mistakenly called just “asphalt”, adds asphalt mineral (bitumen) to the concrete mix, which results in the darker, more durable material you commonly see on sidewalks and roads. Asphalt concrete will tolerate higher pressures than 1:2:4 concrete.
Pervious concrete (opens in a new tab) uses no sand. Instead, coarse aggregates are added to the concrete mix. This formula results in a more porous structure of the concrete and allows standing water to readily pass through it (up to gallons per minute). Therefore, it is often used in the construction of roads, pavements, but in some cases, may be found in driveways as well.
Pervious concrete can be treated as concrete, since it still is quite durable. However, sealing pervious concrete is not advised, as it will seal its pores.
Decorative concrete (opens in a new tab) has become popular both in consumer households and public areas. Decorative concrete is a very broad term which refers to concrete that has been modified cosmetically by e.g., acid staining, coating, polishing, stressing, dyeing, stamping but also overlaying by various polymers.
It would make for a long list if we were to cover all the decorative concrete surfaces and, moreover, it would be a fool’s errand to do so. Each of these surfaces is crafted uniquely, sometimes even by skilled artists.
Therefore, we only give the following tip: Refer to official flyers, handouts or websites to find out the most suitable way of cleaning a particular surface. Better yet, reach out to customer support or perhaps even the artist who has produced the piece if you’re dealing with some high-end stuff.
Never attempt to pressure wash decorative concrete unless you know it’s safe and only used care products suitable for the specific type of concrete surface.
How often Should I Pressure Wash Concrete?
Concrete should be pressure washed and resealed once per year or two. Cleaning can be done more often if the surface is dirty. If you are using a surface-based sealing agent, resealing should be done after each cleaning. Vice versa, it is unnecessary to reseal after each cleaning if deep acting sealing agents (silicones) are used.
When Should I Pressure Wash Concrete?
Check out the weather forecast in your area before planning to pressure wash to avoid rain, but also direct sunlight. Expect to spend several hours on the task, including prepping the area. Don’t forget to also account for resealing, which should be done a few days after the cleaning, when the concrete has dried out.
What Tip Should I Use for Pressure Washing Concrete?
A pressure washer’s nozzle determines the force upon impact by its water stream. If possible, always go for the 65° (soap) fan tip when applying detergents and 40° or 25° fan tips for rinsing.
Spot cleaning of durable concrete surfaces may be done with lower angle tips. However, avoid using 0° tips unless you really know what you’re doing, as they may carve through concrete if used incorrectly and if the applied pressure is too high. Spot cleaning is always safest done by hand. If you don’t feel like getting down on your knees, 15° fan tips are the lowest angle you should go for.
Turbo tips may be applicable to more durable concrete surfaces and foam cannon attachments come in quite handy when applying detergents.
What Pressure Setting Should I Use for Concrete?
Concrete is not the most delicate material out there and will tolerate high-pressure settings. Moreover, concrete has a very rugged surface that may be hard to clean thoroughly at lower pressure settings. Many sources recommend going for roughly 2000 psi if possible, some sources recommend going as high as 3000 psi (opens in a new tab). Therefore, our recommended pressure range would be anywhere between 2000 and 3000 psi.
What Products Should I Use for Concrete?
Every surface has different specifics. Some chemicals may damage particular surfaces, or vice versa, be too mild to properly clean them. Whether you like it or not, your basic kitchen cleaner just won’t cut it and you must buy a specialized detergent for each surface you’ll be cleaning.
There are many detergents for concrete available at any hardware or gardening store, usually simply distinguished as “concrete detergent” or “concrete cleaner”, ranging in strength from mild (pH-neutral) to intense (acidic). Keep in mind that “intense” detergents may discolor the concrete. If you’re dealing with pervious concrete, limecrete, or perhaps decorative adjustments to the concrete’s surface, double-check that the detergent is suitable for your specific surface.
Concrete degreasers (opens in a new tab) (also alkaline concrete detergent/cleaner) is a specialized detergent which is designed to leech out non-polar (oil) stains from the concrete. It is a quite aggressive alkaline solution that may bleach the concrete and results in uneven staining. Therefore, it should always be used with care. In addition, it may be used after applying the intense acidic cleaner to neutralize the surface and actually prevent staining.
Enzymatic cleaners are a good alternative to the aforementioned cleaners, as they are pH neutral, yet quite effective at dealing with tougher stains. Instead of acids or bases, they use enzymatic solutions which biochemically break down organic matter, such as oils and grease, but also pet urine. They are environmentally friendly and are less likely to bleach or stain concrete.
Concrete sealant (or concrete sealer, depending on who you ask), is a chemical mixture that seals the pores of concrete and prevents moisture and minerals leaching into its depths. Although it is generally recommended to seal concrete, in some areas, especially where pervious concrete or limecrete is used, reducing the porosity of concrete is unwanted (e.g., in heated surfaces, or where the surface should drain off standing water). Therefore, consider the material and its properties before applying sealants.
Note that not all sealers are the same. Silicone sealers penetrate and thoroughly seal up the concrete’s pores without leaving any marks on the surface. They are usually used outdoors.
Acrylic, polyurethane and epoxy sealers stay mostly on the surface of the concrete, creating a shiny or matte finish (there’s a large variety of products with different finishes available on the market). However, surface sealers also wear off faster and in addition, polyurethanes are moisture intolerant until cured. Therefore, these types of sealants are usually used indoors.
How to Pressure Wash Concrete
With the preliminaries covered, now it’s time to learn how to pressure wash concrete! Although concrete is quite a forgiving material, for the best results and your own safety, you should do the job carefully and properly, as explained herein.
Learn how to use your pressure washer and all your cleaning products, safely
Read all the manuals, flyers and instructions on each piece of equipment and product you’ll be using. Read how to operate your pressure washer, safety guidelines and learn what personal protective equipment (PPE) must be worn. Do the same for all the products you’ll be using, including both detergents and sealants.
How long should you let the detergent sit on the surface? Are the detergent and the sealant suitable for your type of concrete? Is it safe to use your detergent in a pressure washer? What hazard statements are included on the detergent’s bottle and what precautions must be taken when using it?
Those are just some of the questions that you should be comfortable answering before proceeding further.
Clear and Prep Your Work Area
A pressure washer can cause havoc to its surroundings. As a rule of thumb, the washer’s water stream should never come close to anything but a clear surface. Move out any objects on the, or surrounding the surface. Cover nearby plants and any other immovable objects with plastic covers. Sweep the surface, or use a leaf blower (opens in a new tab), to clear out leaves and debris. Only then proceed to use your pressure washer.
Test your Pressure Setting, Nozzles and Detergent
Whenever you switch to a new setting or apply a new product, you should first test it out on a small, discrete area of the surface you’ll be cleaning, to see if it doesn’t damage it, discolor it, etc.
Keep Your Tip Far from the Ground and Moving
Keep the gun roughly 2 feet above the surface and move it lower only if you feel it’s not effective. Never move closer than 6 inches above the surface. Stick to the same distance when cleaning. Keep your gun always moving and never point the pressure washer at a single spot for too long, especially if using a low angle fan tip!
Apply Concrete Detergent and Don’t Let It Dry
Concrete detergent must be applied as per the manufacturer’s instructions which are usually found on its bottle. Detergents are always applied either by a 65° (soap) fan tip or a foam cannon.
Choose your detergent wisely, based on how dirty and stained the concrete surface is. Detergent should be left to work on the surface for an appropriate time, always given by the manufacturer, but never left to dry.
It may also be necessary to use a brush to properly clean the surface’s corners or crevices (e.g., between concrete blocks). When done, rinse the entire surface thoroughly with a 40° fan tip. 25° fan tips and 15° fan tips may be used where appropriate. Prior testing is always advised.
Let Concrete Dry Before Applying Sealant
Concrete should be left to dry which may take up to 3 days. Make sure to use sealants only where appropriate, as discussed above, and always stick to the manufacturer’s instructions when doing so.
In summary, although concrete is quite a forgiving material when it comes to applied pressure, the same doesn’t apply to the products you’ll be using to clean it. You must always balance out the risk of chemical damage to the surface and the efficacy of your cleaning protocol.
Pressure washing concrete requires you to know quite a bit about the exact type of concrete surface you are dealing with. Choice of detergent depending will depend on concrete properties, but also the amount of dirt and stains you need to get rid of. Concrete sealants should be applied where necessary (usually all driveways) and avoided where not (limecrete, pervious concrete). Manufacturer’s instructions and guidelines of each product must be respected, including safety tips and recommended PPE.