8 Best Treatment for Greenhouse Wood [Most Effective Ways]

Your greenhouse wood requires protection against UV damage and moisture to prevent fungi, decay, and mold infestations. However, for long-lasting protection, you must use the proper treatment. But what is the best treatment for greenhouse wood?

There are several preservative options available. You could use copper-based pressure treatments, wood tar, oil finishes, varnish, borax, or wood paint. All these treatment options will ensure your wood lasts for many decades.

Now, without further ado, here is a detailed look at the best greenhouse wood treatments, including how long they can last.

Best Treatment for Greenhouse Wood

Greenhouse wood is highly porous. Therefore, without proper treatment, it may suffer from rotting and warping because of exposure to moisture and sun. So, how do you protect wood in a greenhouse? Let’s check out some of the best treatment options available.

1. Wood paint

Painting your wooden greenhouse can help protect it from the harsh effects of sun and weather. Some of the best wood paints boast water-repellent and stain-resistant properties for maximum protection. You just need to apply 2 to 3 protective coats of clear water-based wood paint that is UV-resistant on your greenhouse wood.

However, not all the paint for greenhouse wood offers the best protection. So, some of the best products you could use include;

  • Acrylic paint
  • Semi or high-gloss paint
  • Linseed oil paint

2. Oil finishes or sealers

You see, oils are known to repel moisture and offer UV protection when blended with resins. Therefore, you can prepare your own oil finish as a treatment for your greenhouse wood at home. However, you must mix the oils with mineral spirits to prevent stickiness and speed up drying times. Some of the best natural oils to protect the wood in a greenhouse include:

  • Tung oil
  • Linseed, also known as flaxseed oil
  • Walnut and soy oil
  • Danish oil
  • Refined hemp

Now, for the best results, you must apply these wood oils in thin and even coats. More importantly, you should allow enough drying time before reapplying another coat.

3. Wood varnish

Besides enhancing the appearance of your greenhouse timber, wood varnish also provides a protective coating for wood. For example, the marine varnish is made with UV absorbers to withstand sun damage.

Basically, treating your wood with varnish makes your greenhouse water and weatherproof. Consequently, this helps prevent rotting, peeling, cracking, or flaking issues. The best part about this greenhouse wood preservative is that it comes in many types to choose from like:

  • Water or marine varnishes
  • Spirit or polyurethane varnish coating
  • Oil and clear varnishes
  • Turpentine
  • Acrylic varnish

4. Wood preservatives

Wood preservers are formulated to soak deep into greenhouse wood to protect against rot and insect attacks. The best greenhouse wood preservative also protects against fungi, mold, and algae. However, I suggest reapplying the preservatives every two years for the best results. Now, if you are looking for the best wood preservers to keep away woodworms, you can try out:

  • Barrettine Premier Colors
  • Ronseal Total Colored or Clear preservative
  • Sadolin Quick Drying preserver
  • Sikagard Wood Preserver

5. Copper-based pressure treatments

These types of treatment involve forcing copper-based chemicals into the greenhouse wood under pressure. Consequently, this helps ensure the chemicals penetrate the wood’s surface, offering long-lasting protection against insect infestation and rotting.

According to the EPA (the United States Environmental Protection Agency), some of the safest copper-based chemicals to use for pressure treatment include:

  • Alkaline copper quaternary (ACQ)
  • Copper-HDO
  • Copper azole
  • Copper naphthenate
  • Polymeric betaine

6. Wood stains

Wood stains are pigmented paint for greenhouse wood designed to enhance the look of timber and protect it. Like other treatments for greenhouse wood, wood stains boast water-repellency properties and are also resilient to other weather elements. However, you must reapply the treatment at least every 3-5 years to ensure long-life protection. Check out this list of the best types of wood stains:

  • Oil-based stains
  • Gel-based stains
  • Water-based stains
  • Lacquer wood finish

7. Wood tar

Wood tar is yet another excellent preservative for greenhouse wood. When you apply it to timber, it creates a water-repellent barrier against moisture. Even better, you can expect this treatment to guard your wood against fungi, insects attack, sunlight, and weathering.

Before applying wood tar, I suggest you dilute it with 50% linseed oil or 20% gum turpentine. Then, ensure it is warm up to 60 degrees Celsius. Some of the commonly used wood tar types to protect wood in a greenhouse include:

  • Pine or Stockholm tar
  • Crude wood tar
  • Lumber tar
  • Resinous tars

8. Borate compound

This greenhouse wood preservative is perhaps one of the most effective termite repellents. When you spray borate compound on greenhouse timber, it soaks to guard the wood against fungal decay and wood-decomposing organisms. But to ensure long-lasting protection, I recommend you paint or stain your wood after using the borate treatment.

How Do You Prepare Greenhouse Wood For Treatment?

Before treating your wood, wash it using the best multicide or fungicidal wood cleaner. This helps remove any organic growth like algae, moss, and fungi. Next, give the wood a light sanding to remove previous coats or paint before leaving it to dry for at least 24 hours.

How Long Does Treatment Last On Greenhouse Wood?

The time varies based on the type of treatment you use and the climate. For example, the preservative can last a lifetime if using copper-based pressure treatments. However, treatments like wood preservers require re-coating every year or two.

And when it comes to wood paint for greenhouse wood, it can last between 5 and 7 years. As for wood stains and oils, you might have to reapply them after 2 to 3 years. On the other hand, wood varnish treatment could last up to 10 years or more.

Which Is The Best Greenhouse Wood?

So, what kind of wood is used for greenhouses? The best wood is highly resistant to insects, moisture, rot, and fungal attacks like redwood or cedar. Other types of wood you can use include:

  • Osage orange
  • Black locust
  • Black walnut
  • Cypress
  • Pacific Yew


Treated wood for a greenhouse offers many benefits. So, let’s look at commonly asked questions about greenhouse wood treatments.

Should I paint greenhouse wood?

Yes. Painting your greenhouse wood is the only way to ensure it lasts long. This is because paint for greenhouse wood offers superior protection against moisture, rot, and sun fading.

Are wooden greenhouses any good?

Yes, because wood boasts natural insulation properties. Therefore, during the winter, wooden greenhouses require less energy for heating. Even better, you can expect the greenhouse to stay cool in summer.

How safe is pressure-treated greenhouse wood?

Depending on the preservative, pressure-treated wood for the greenhouse can be toxic or non-toxic. For example, chromated copper arsenate and pentachlorophenol are poisonous wood preservatives. However, you can safely use Copper Azole, copper naphthenate, and alkaline copper quaternary to pressure-treat your greenhouse wood.

Treated or untreated greenhouse wood?

You can use any of them. If using untreated wood, you must treat it to guard the timber against mold and insect damage. But for treated wood for a greenhouse, you won’t have to use any treatment. This is because it is not susceptible to rotting, fungus, and sun damage.


The best treatment for greenhouse wood should offer maximum protection against most weathering elements, decaying, and insect attacks. Concerning this, you could use oil sealers, preservatives, varnish, wood stains, wood tar, borate compounds, and pressure treatments.

But before applying these treatments, you must prepare the wood properly by cleaning and sanding the timber. Doing so will ensure the preservatives last for several years before needing reapplying. Using the best wood also helps ensure your greenhouse is not susceptible to damage.

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