Pressure Washing Stained Siding

Pressure washing stained siding is all about removing dust and dirt, opening the woods pores and getting rid of the old burned up stain. This is the starting point for restaining a home with unpainted wood siding, soffits and trim. A pressure washer can be used on any type of exterior wood siding including cedar shake or rough sawn cedar siding and T1-11 wood siding.

There are several considerations before getting started. The exact procedures you will use depend on the condition of the old stain and the type of new stain that will be applied.

The Ins and Outs of Pressure Washing Stained Siding

First, this is and always has been a dangerous machine. Fortunately, most of the danger is confined to the siding or other objects that are in the way of the pressurized spray. A good amount of pressure is needed, at least 2000 psi, and a volume of 3-4 gallons per minute (gpm) output. This means a powerful pressure washer is needed.

The best spray tips for the job are either the 40° or 25° degree. The 40° degree tip will distribute the spray over a wider area thus minimizing any damage. The 25° degree can be used for stubborn areas. You also will have 2 other tips, 15° degree and 0° degree. These shouldn't be used for pressure washing stained siding, especially the 0° degree tip.

The amount of washing needed depends on the old stain and the condition of the wood siding plus the new stain color and how much it can hide. Three things affect the amount of washing needed.

• If the siding has visible mold.
• If the old stain has turned into a powder.
• If the new stain color is the same as the old or even lighter.

Mold Growth

Visible mold growth must be removed with bleach and water. Some specialty products can be injected through the pressure washer. It is important to keep the siding wet for 15-20 minutes so the cleaner can do it job.

Burned-up Old Stain

Often the old stain is turned into a powder and basically burned up by sunlight. This is a condition I often see. In this case pressure washing stained siding is easy although labor intensive. All you need is the pressure washer and water. Usually soaps and cleaners are not needed. The stain easily comes out of the wood siding.

Stain Color

The new stain color has an effect on the volume of work needed. Basically it's very simple.

If the new stain is lightly pigmented and the old stain isn't, then all of the old stain must be removed. Truly fresh and clean wood free of any old stain is needed. This way the new stain color won’t be affected by the old. In this case start with plain water and see how the stain comes off. Often plain water and the pressure washer is all that is needed.

If the old stain is stubborn then a siding cleaner/stripper will be needed. Use a type that can be injected directly into the washer. These work well most of the time, but will add to the overall cost plus they will slow down the washing process.

If the new stain has more pigment or is a darker color than the old, then less washing is needed. In this case remove all loose stain and most of its color. The new stain will cover any remaining color. You just need a clean porous surface for deep penetration.

The Basics for Pressure Washing Stained Siding

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Now that you have an understanding of some situations that require special treatment, you are now ready for the basic instructions. Understand and follow these instructions so damage can be avoided.

• Close and lock all windows before starting. You shouldn't wash windows directly with the pressure washer, but you will need to rinse off the residue coming the siding. Do not rinse any windows that are known to leak. Doors also need to be shut and rinsed.
• Avoid direct washing the outlets and exterior lighting fixtures. Lighting fixtures can be removed prior to washing, but the opening should be plugged with paper or plastic bags to keep the bulk of the water out.
• Do not spray directly into soffit or gable end vents. Carefully wash around these areas.
• Do not pull the trigger while pointing the tip directly at the siding. Point the tip away or at an angle with 2-3 feet of distance. This will minimize damage to the wood.
• After the trigger is pulled, carefully bring the tip within 10-12 inches and begin washing. Use a fluid motion that follows the wood grain. Plus, always keep the tip moving. Stopping in one spot with the pressure engaged could leave an indentation in the wood.
• Apply cleaners from the bottom up; allow soaking according to the manufactures directions and then rinsing from the top down.
• For water only washing, begin quickly washing from the ground up. This will inject water behind the stain and then do the full hard washing of the top down. Most exterior wood stains will be easily removed. Repeat the washing from the top down if need, heavy or stubborn deposits.

Follow these recommendations when pressure washing stained siding and modify as needed. Some steps won't apply to every side of your home, so you will have to be observant of how the stain is coming out of the wood.