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Perma-Chink Technical Tips. 2008

Pressure Washing Tips:


By Jeff Kyger, Northwest Log Home Care Bellevue, Washington.

Pressure washing (also referred to power washing) is the function of using highly pressurized water to remove mildew, mold, dirt, pollens, UV graying, etc. You'll hear different recommendations whether or not pressure washing your logs is the best cleansing method. Generally speaking, pressure washing is the quickest and least expensive choice.

A combination of the amount of pressure and amount of water the equipment is designed to use will determine the result, along with other factors. One fallacy is that you are saturating and “damaging" your logs with water as a result of pressure washing. This simply isn't true. On hard, sound, rot-free logs, you are only introducing water into the top fibers of the wood. Your decision should be dependent on the results you want and whether or not your gaps are conducive to allowing water in your home.

If you choose to go with a pressure washing, and your home has numerous gaps that will allow water to infiltrate, foam backing rod (the same product which is used prior to chinking) can easily be used which can be plugged in place before water is introduced. Results will vary tremendously depending on the following conditions:

  • The strength of the pressure used (also known as PSI/pounds per square inch).
  • The GPM (gallons per minute) the machine discharges.
  • Type and amount of product (previously applied stain/sealer) being removed.
  • Age of the logs (often relative to surface hardness).
  • Experience of the operator.
  • Angle at which the wall is sprayed.
  • Distance the tip is kept from the wood.
  • hether a chemical stripper is first applied.

PSI & GPM
Both PSI & GPM are the important factors for the optimum performance when pressure washing. The pressure washer's PSI rating is the maximum amount of force (pressure) discharged by the pressure washer. Pressure washers range from 1,000 psi up to 4,000 psi. A low setting of 1000 - 1500 psi could be sufficient to simply remove minor UV graying that's taken place. However, this isn't enough to remove an existing stain or sealer, in most cases. Something closer to 2500 - 3200 psi, or higher, is necessary on many homes. Often the 3,800 psi setting is reserved for driveways, concrete walkways, etc. although this can be used on logs as well, and with great success; just be careful not to get the tip too close to the wood in order to eliminate any fuzzing. For comparison purposes, a typical household faucet will generally create 40-60 psi. The GPM (the machine water flow during one minute of operation) is also vitally important.

Product Being Removed
The time it takes to pressure wash and the results generated are often directly associated with the type of finish being removed as well as how many coats have been applied. While some older, obsolete linseed based oil stains are more difficult to remove than newer products, practically everything can be removed with proper pressure washing techniques. Some of these older type products will often need a chemical stripper applied first in order to soften the bond to the wood.

Condition of Wood Surface Traditionally, newer, recently peeled logs have a greater surface hardness and can withstand highly aggressive pressure washing (if needed) easier than a wall which has been fully exposed to direct sun for 20 years. On older/softer logs, less psi is often used in order to help eliminate any fuzzing of the wood that otherwise can be caused by improper pressure washing. The effective psi can be adjusted simply by moving closer or standing back a bit further from the surface. You might notice your upper and lower fascia boards have aged and darkened at an accelerated rate compared to your logs. Because these areas are often made from softer (i.e. pine) wood, they are more likely to absorb water leading to more prominent mildew growth. These areas are also washed and can easily resemble new wood once cleaned.

Experience of Operator
One key element of this process is the speed (whether slow or fast) at which the tip moves along the wood surface. Take a tremendous amount of care and precautions to leave your logs in the best condition possible. A key element is to always “keep the wand moving". Keeping the tip stationary, or even slowing down too much can leave "fan lines" or marks in the wood left by the water pressure. When conditions are necessary, change the angle at which the pressure washing wand is held and the distance it is held from the log in order to achieve optimum results.

New Construction
Pressure washing of new constructions can also easily remove the UV graying of the logs that can start occurring just weeks after the logs are stacked, particularly if exposed to direct sunlight. The interior of these projects are often pressure washed as well, particularly if the walls are standing for a lengthy period of time prior to the roof being installed. This exposure could cause some mold, mildew as well as UV graying to form, particularly in a damp or humid environment.

Drying Time
Depending on temperature, humidity and the condition of your logs, they can be stained as early as a day after pressure washing. There will be some cases when the stain can be applied the same day they've been pressure washed (but don't rush the process). For this to happen, very high temperatures are needed (usually over 80 degrees). At times a week or more may be necessary to wait. You'll need to wait until the wood is dry enough to accept the stain since excessive moisture can inhibit the saturation of the stain into the wood or its bonding requirements to the wood fibers.

Other Notes
In addition to log and wood sided structures, other areas where pressure washing can be utilized include driveways, stone walkways, pool decking, stone walls, fencing, gutters, downspouts, roofing and other areas. Concrete slowly builds up a browning/green appearance over time which usually consists of grease, dirt, mildew and algae which can easily be cleansed. This is often not so recognizable (until its cleaned) since it builds up slowly over a period of time.

Pressure washing can be done in practically any temperature and weather conditions. Its application isn't isolated to warm, dry conditions as other segments of the restoration process is although chemical strippers, which are often applied prior to cleaning, work much better in warmer weather. Whether you hire a professional or undertake the project yourself, pressure washing can bring back the beauty of your logs, preparing them for a fresh coat of stain and protective clear coat finish.

Northwest Log Home Care Bellevue, Washington.