TWP Stains and Moisture Content

by TWP Help

Last Updated on January 19, 2021 by TWP Help

Moisture Content of Wood When Applying TWP

Whether the wood you are staining is new or more aged, the moisture content is an important factor in the timing of stain application. Applying TWP or most any wood stain for that matter to a wood surface that is still holding too much moisture can result in many problematic issues. Trapping moisture in wood can promote the growth of mold and mildew. A moist and mildew infected environment can lead to wood decay and rot. This should be avoided at all costs. Wood rot will most likely progress to structural damage causing expensive repairs and replacements.

After the wood surface has been cleaned and prepped correctly prior to staining, it should be allowed to air dry for several days depending on the age, condition, and porosity of the wood. A good rule of thumb is to let the surface dry for several days before staining and do not stain if rain is expected. A deck that is mostly shaded may take a day or two longer to dry than a deck that sits in full sun all day. Weather and climate can also be a factor.

To determine the exact moisture content of a wood surface, a moisture meter can be used. They are fairly inexpensive and easy to use. Just probe the wood in several different areas to get an average reading. The moisture content of wood when applying TWP should be 15% or less. A higher moisture content than that may lead to mold and mildew problems and jeopardize the integrity of the stain’s finish and performance.

It is best to be patient and not rush the application process of TWP by applying it to wood that is still too high in moisture. This applies to new wood as well. New wood is often referred to as “green” wood because it has not yet dried out. The moisture content in new wood can be very high even though it may appear dry on the surface. Allowing the new wood to age for 6 months or more may be necessary to achieve the desired moisture content prior to applying TWP stain.


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I checked the moisture content of my covered deck. I have a mix of 38 year old cedar and 1 year old cedar. Cleaned and brightened the deck over 2 weeks ago the moisture meter comes up with a range percentages from 15% to 18%. I have a few lengths of both new and old wood stored in my garage and the both measure at 8% to 10%. Should I wait longer until the content is around 12% ?


So, I emailed back in July under Best Prep for TWP Stains. I followed instructions to the letter and we hadn’t had rain for days when I applied TWP100. Well, the rains have returned to the Seattle area and it appears I am getting black mold. Needless to say after all the prep work, I am not pleased. I attach photos for your reference. The railing and picture frame border is western red cedar. The decking is Alaskan White cedar. I did only one coat on the white Cedar as it wasn’t absorbing much stain. The border and rails I… Read more »


How many coats for PT pine that has had no previous stain/sealer? It is about 2 years old. Do you recommend the 1 or “wet on wet application”?