Evaluating Log Finishes

Home inspectors are typically not present when old finish removal and re-application or the original application are performed. Because improper procedures followed during finish removal, surface preparation and finish re-application may not be readily discernable through a visual inspection by a general home inspector, Inspectors should disclaim proper application procedures.

Inspection Contract and report language should make it clear that the scope of the inspection is limited when inspecting finishes:

• The Inspector is not required to identify the finish coating type.
• The Inspector is not required to identify the cause of any finish failure.
• The Inspector is not required to confirm proper removal, preparation for or application of finish coats.

Sample Disclaimer

“The result of any improper procedures followed during finish removal, log surface preparation for and/or application or re-application of finish coatings may not have been readily discernable through a visual inspection at the time of the inspection. The General Home Inspection is limited to log finish coat condition and defects visible at the time of the inspection only and the Inspector disclaims confirmation of the proper finish removal, preparation for, application or re-application of the finish coatings in place at the time of the inspection.”

Inspectors should have any disclaimer approved by their attorney before including it in a Contract or Inspection Report.

WATER REPELLENCE

TESTING PENETRATING FINISHES

The finish should prevent water in its liquid for from reaching wood fibers. Inspectors can test the condition of the finish by spraying logs with water. Water should form beads on the surface. If water is absorbed into the wood, recommend maintenance. This test works well for penetrating finishes.

 Courtesy of Permachink Inc.

Water forms beads on the surface                                                                    Water is absorbed

TESTING FILM-FORMING FINISHES

A method for testing film-forming exterior finishes is to press masking tape firmly to the log surface. If when you remove the tape 50% or more of the finish is removed with the tape, recommend maintenance.

FINISH REMOVAL METHODS

Although making recommendations concerning the best methods for removing finishes lies beyond the scope of the General Home Inspection, inspectors will be asked by clients and should be aware of the various methods used. When removal is performed improperly, defects may be created which inspectors will want to be able to recognize.

POWER WASHING

Power washing can work well if sealants such as chinking and interior gaskets are in good condition. Used improperly, pressure washing can damage chinking or finishes which are still in good condition. Although the fact that water is chemical-free is an advantage, pressure-washing can raise grain and wood fibers enough to require sanding before new finish is applied.

SANDING or GRINDING

Sanding or grinding requires practice as inexperience may cause some people to remove more material than is required or damage material which should not have been touched, such as chinking.

CHEMICAL STRIPPERS or CLEANERS

Chemical strippers can alter wood pH, which should be restored before the finish is applied. Also, removal of the stripper or cleaner usually requires power washing.

Although for many years a bleach solution was the standard recommendation for cleaning logs, less toxic chemicals are available now. Bleach can damage finishes if residue is not completely removed and bleach also sometimes reacts with iron tannates naturally present in wood to produce discoloration which can be tricky to recognize and remove. Oxalic acid is one method used for removal.

MEDIA BLASTING

Sand used in sandblasting is usually too abrasive for use in removing wood finishes and will remove earlywood, leaving harder latewood ridges and an uneven surface.

• Corncob is the media used most widely for removing finishes and discoloration from home logs.  Corn cob is non-toxic, virtually dust-free and biodegradable. It will roughen the surface texture of wood to a degree depending on the grit size used, the wood species and condition of the logs.
• Walnut shells are more abrasive than corn cob and will strip finishes more quickly but can roughen wood surfaces more than corn cob. Walnut shells leave an oil residue on log surfaces which may degrade the adhesion of finish coats (depending on type) or chinking.
• Potassium sulfate- a very hard salt chrystal, is more abrasive than either corn cob or walnut shell.
• Sodium bicarbonate (baking soda) can be used to blast walls which have been fire-damaged and is very effective in reducing odor.

courtesy of Permachink Inc. 

Blasted/not-blasted                                                         A blasted surface magnified

 Corn media blasting has become common and does a good job of removing finishes without using water or chemicals. The downside of blasting is that it does change the surface of wood somewhat, sometimes requiring sanding after blasting is complete due to some raising of the grain and pitting of the wood surface (photos above).

FINISH PROBLEMS

Inspectors are looking for moisture intrusion of the finish coat. One of the common signs of moisture intrusion of the finish coat is discoloration caused by fungal activity.

Courtesy of Permachink Inc. 

These photos both show the results of moisture intrusion of a film-forming finish.

For many years a bleach solution was the common recommendation for removing discoloration from logs, especially when fungi were the source of discoloration.

Any bleach residue remaining on the logs can cause deterioration of the finish coat, as seen in the photo to the right.

Courtesy of Permachink Inc.

The streaky staining in the photo to the right is the result of bleach used for cleaning reacting with iron tannates naturally present in the wood.

Bleach/iron tannates stains are usually streaky or blotchy and fade around the edges. Mold discoloration is usually round with well-defined edges.

Cleaners based on oxalic acid must be used to remove tannate staining.

                                              courtesy of Permachink Inc.

Ultra violet (UV) damage visible in the photo to the right is the result of lack of protection from direct sunlight.

UV-damaged wood cells can provide food for some types of fungi.

 courtesy of Permachink Inc.                                              

If an inspector is unsure about the composition and condition of the finish material, this should be stated in the inspection report and a specialist inspection should be recommended if a problem appears to exist.