If you’ve hired a painter to paint your wood home during the shoulder seasons (Spring or Fall) and they haven’t checked the moisture content of the wood prior to painting, it’s a red flag. The video above and content in this article will help you understand how to check moisture in wood using a moisture meter.
Painting over wet wood is one of the biggest blunders new painters and DIYers make. It’s true! And sadly these days, many untrained painters don’t even know why this is important.
When you prime or paint overtop wet surfaces, the water content in the wood evaporates and causes the paint to peel, defeating the purpose of your hard work.
To avoid the frustration of premature paint failure, it’s crucial to test the wood substrate before diving into your next painting project. This is where a $30 moisture meter can make the difference between a paint coating that lasts 1 year or 10 years.
Table of Contents
- Why Test for Moisture Content?
- How to Use a Moisture Meter
- Acceptable Moisture Content Levels for Painting Wood
- Benefits of Using a Moisture Meter
- Common Mistakes to Avoid
- FAQ
Why Test for Moisture Content?
If you want your paint coating to last a long time, never paint over wet wood.
Professional painters who care about their work (and your home) use moisture readers to determine the moisture content of wood before applying any paint coatings.
It’s simply because water (aka moisture) is the leading cause of paint failure on most surfaces. And because most retail paint products are water based (as opposed to oil based paint), water is literally the enemy of a strong paint coating.
Water ingress (or also in the form of vapour) breaks the stong bond between the paint coating and the dry substrate. And once this strong bond is broken, it allows the trapped moisture under the paint coating to continue breaking the bond elsewhere on the same surface.
The general rule of thumb is to ensure that the moisture content is below 15%.
Any reading higher than 15% moisture content will likely lead to a disaster, and trust me, you don’t want to be the homeowner left with peeling paint and regrets!
How To Check Moisture In Wood
Using a moisture meter is straightforward. Simply insert the probes into the wood to get a reading. For instance, if you poke the meter into the wood and it shows around 30%, you know it’s too wet to paint. Ideally, you want readings closer to 10-15%. If it’s higher, let the wood dry out before proceeding.
Here’s a quick tip: always check the end grains of the wood, as they tend to soak up moisture more than other parts. If you find readings climbing above 15%, it’s best to wait a bit longer. Patience is key in this game!
Acceptable Moisture Content Levels for Painting Wood
| Season | Relative Humidity | Acceptable Moisture Content for Painting |
|---|---|---|
| Winter | 30-50% | Below 15% |
| Spring | 40-60% | Below 15% |
| Summer | 50-70% | Below 12% |
| Fall | 30-50% | Below 15% |
Common Surfaces to Check
Here’s a few common surfaces and areas you should diligently check prior to applying a primer, paint or stain coating:
- Ends of Fascia Boards: This is a very common area that gets neglected when painting. If the end of your fascia board (aka – Rake) is missing a roof shingle then it’s likely going to have higher moisture content.
($1000 Tip: to avoid unnecessary wood rot on the ends of your fascia boards, make sure to have a piece of roof shingle or rain diverter installed to protect the wood.)
- Wood Decks and Steps: This is especially true if you’ve recently just built a new wood deck or steps. Make sure you test multiple areas including the hand railing, lowest step, and support posts.
- Window Ledges: Window ledges that are exposed to rainfall should definitely be checked. Especially horizontal window ledges that don’t have much of a slope to allow the rainwater to runoff the wood.
- Gutter Boards: It’s very common for gutter boards (the board holding up the gutter) to be exposed to moisture. Whether it’s from a leaky gutter or a constant drip of water from the roof shingles, make sure to test the moisture of the wood prior to painting gutter boards.
- Pressure Treated Wood: Pressure treated wood is wood that is injected with deep penetration and retention of liquid preservatives to help prevent wood. This type of wood is either green or brown in color. Never apply a paint coating to newly installed pressure treated wood. It’s best to allow up to 6 months of dry time prior to applying any coatings.
Benefits of Using a Moisture Meter
- Prevents Paint Failure: Ensures a solid bond between the wood and paint.
- Cost-Effective: Saves you from costly repainting and repairs.
- Increases Longevity: Properly prepared surfaces last longer.
- Easy to Use: Quick readings that can be done in minutes!
Common Mistakes to Avoid
Don’t fall into the trap of ignoring moisture levels! Here are a few common pitfalls:
- Painting immediately after rain—give it time to dry!
- Skipping the moisture reading altogether—this is a vital step!
- Assuming all wood is dry—different areas can have varying moisture levels.
- Painting newly installed pressure treated wood—it can take 6 months to 1 year for pressure treated wood to allow paint coatings.
(Tip: To see if pressure treated wood is ready for paint coatings, perform a water drop test. Simply drop a few drops of water onto the pressure treated wood. If the drops of water bead up – it’s not ready for paint. If the water drops immediately soak into the wood, it’s ready for paint.)
FAQ
- What is the ideal moisture content for painting wood?
Ideally, your moisture meter should show readings below 15%. Anywhere between 5-10% is ideal. - Can I use a moisture meter on other materials?
Yes, it can be used on stucco, hardy board siding, and even your finger – ouch! - How often should I check moisture levels?
Always check before painting or staining wood surfaces. This is especially true if you’re painting in the shoulder seasons of March to June (Spring) or September to November (Fall).
In conclusion, using a moisture meter is a simple yet effective way to ensure a successful painting project.
If you have any questions or need assistance with your painting project, don’t hesitate to contact Trusted House Painter at 1-866-PAINT-18.
Our free hotline for homeowners is designed to provide helpful and reliable advice when you need it the most. (Yes, you speak to an actual person – not an AI bot!)
Trusted House Painter can also help you find local painters through their search directory for free!
You can also visit our Trusted House Painter YouTube channel for more helpful DIY related painting videos. (Remember to like and subscribe!)
Remember, the key to a successful paint job is preparation. So, avoid the pitfalls of painting wet wood and keep your projects looking fresh and fabulous!
For more tips on painting, check out these resources:
- Transform your home with professional exterior and garage painting services.
- Read our How to Paint a Garage Door posts here.
- Transcript of the YouTube Video “How to Paint a Concrete Garage Floor”.
- Important tips for painting your garage door.
Happy painting!
