When to Pressure Wash Decks

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Pressure washers are powerful cleaning tools, and they are particularly effective on decks. A common question though is when to do this. Sure you can pressure wash anytime, but when is the optimum time to do this?

Decks should be pressure washed in spring to remove snow debris, and also in the fall just before winter sets in. It is also a good idea to pressure wash if you are going to stain the deck.

Now that you know when, I will show how to pressure wash a deck step by step. It should only take an hour to finish washing, and 2- 3 hours or so to dry.

Note: pressure washers can only be used on natural wood decks. I do not recommend pressure washing composite materials as they are too light. Use a garden hose instead.

Required Tools and Materials

  • Pressure washer
  • Safety glasses
  • Gloves
  • Shoes
  • Soap or deck cleaning detergent (Sun Joe SPX is my pick since it is specifically for decks)
  • Drop cloth
  • Broom
  • Mildew / mold cleaning solution like Simple Green Oxy Solve

Step 1: Safety Instructions

Pressure washers are powerful but can be dangerous if not properly handled. You’ll be on a slippery surface and pressurized water can send debris scattering.

To be safe:

  • Wear safety glasses, a long sleeve shirt and shoes.
  • Sweep debris off the deck. You don’t want these flying around when you wash.
  • Avoid washing anywhere near electrical outlets. If there are any in the vicinity, cover securely.
  • Do not let anyone (pets included) near the deck while you pressure wash.
  • Use a drop cloth to cover plants, outdoor furniture and other objects.

Now that you are ready, you can set up the pressure washer.

This video demonstrates how to pressure wash decks safely.

Step 2: Configure the Pressure Washer

Set the pressure washer PSI as low as possible. For pine, spruce, cedar and other soft wood, I suggest 500-600 PSI. For oak, mahogany, teak and other hardwood, 1200-1500 PSI.

Put the white (40 degree) tip on the pressure washer. Turn the machine on and adjust the PSI accordingly. You can also use this tip to pressure wash stucco.

Point the spray wand at an inconspicuous section of the deck. Change the angle and distance until it is as far from the deck surface as possible, but still able to remove dirt. This is the safest approach.

If the pressure washer removes dirt and water doesn’t splash on you, that is the right distance.

Step 3: Prepare the Cleaning Solution

This step is only required if the deck has mildew, mold or other kinds of stain. If not, proceed to step 4.

Some cleaning solutions are already mixed, so you just pour it into the pressure washer dispenser. Others require mixing. Follow the instructions before using it.

Use only cleaners made for pressure washers and the kind of wood deck you have. Not all wood surfaces are the same so choose an appropriate product.

Apply the cleaning solution to the deck. Make sure you get to the nooks and crannies where the stains are. Leave it on the surface for 15 minutes or whatever the product instruction indicates.

Step 4: Rinse the Deck

Begin at the railings and wash the solution thoroughly. Do not leave any behind because it’s going to leave stains when it dries.

Move down and wash one board at a time. Spray horizontally and overlap your sprays. Wash back and forth until you wash away all the detergent. Maintain the distance of the nozzle to the board at all times.

You may need to repeat this depending on the condition of your deck. For tough stains you have to apply the detergent twice and rinse thoroughly.

Step 5: Dry the Deck

Remove the drop cloth on the plants and outdoor furniture. Now you just have to wait for the deck to dry. This can take a couple of hours or longer depending on the weather.

Wait at least two days before you sand, apply any stain or paint. This ensures the wood will not warp.

What Pressure Washer Should I Use on Decks?

There are two options: gas and electric. Some prefer gas pressure washers because you are not constrained by a cord.

Gas pressure washers have adjustable PSI so you can use a lower setting for decks and set it higher for concrete.

Ohers prefer electric pressure washers because it is more affordable than gas models and is still effective.

In my personal experience, it really doesn’t matter. Electric and gas pressure washers will both work.

What’s important is you set the PSI to its lowest possible level. 500-600 for softwood, 1200-1500 PSI for hardwood.

With stucco, soft wood and other delicate materials, you should always use low PSI and a 40 degree nozzle. Keep the tip at least 6 inches from the wood surface to prevent damage.

What Cleaner is Best for Decks?

There are a lot of ready-made products to choose from. You just apply it on the deck, let it rest for 15-20 minutes and rinse.

You can also use the DIY approach. Combine 2 gallons of water with any detergent that is safe for wood. I don’t however, recommend using bleach as it can damage wood.

To keep things simple: use only detergents and cleaners made specifically for wood decks and pressure washers. Apply as directed in the instructions and then pressure wash it.

Do I Need a Scrub Brush When Pressure Washing Decks?

In most cases a brush isn’t necessary. A cleaning detergent should be enough to remove the grime. That along with thorough rinsing will get the job done.

There are exceptions to the rule. If the deck hasn’t been cleaned in a long time, it’s going to be harder to eliminate grime.

In that case you should use a scrub brush. Do not use a 25 degree tip and do not increase the PSI beyond the suggested limit. Doing so can cause permanent damage to the wood.

You can scrub the deck the old fashioned way, getting your hands dirty. Or you can use the M Mingle pressure washer brush attachment which makes your job easier and faster.

Related Questions

How often should I pressure wash a deck?

At the very least twice a year: during spring and before winter comes. But there are other factors to consider.

If the deck is exposed to a lot of dirt, wash it more often so grime doesn’t stick to the surface. If you wait too long it’s going to be harder to remove them.

If dirt dries and sticks to the wood, it might take more pressure to get rid of them. Increasing the pressure can damage wood, so I don’t recommend it. Instead I suggest scrubbing the dirt off with a brush before washing.

Can a pressure washer alone remove mildew?

It’s better to use a cleaner with your pressure washer. Follow the instructions and apply on the wood. Put only as much as needed to avoid damaging the surface.

Can I use bleach to clean a wood deck?

Bleach is too powerful and could leave marks. Only use cleaners formulated for wood decks and pressure washers.

For stubborn grime, brush the surface and combine with washing. Do not increase the PSI beyond the safe limit.

Is it better to sand a deck than pressure wash?

Pressure washing is better for two reasons. Sanding takes more effort than pressure washing. Also if you make a mistake it can damage the wood. Unless you want to renovate the deck, I recommend pressure washing instead.

Can pressure washing with just water clean a deck?

If the surface isn’t too dirty, water alone is fine. For the best results you should at least mix water with any wood-safe detergent.

You only need to use mildew and other cleaners if needed. Inspect the deck first so you will know ahead of time what kind of cleaners are required.