As you begin your gardening journey, you may consider installing a lovely greenhouse alongside your garden. These are great additions for gardeners who wish to protect tender seedlings in early spring or keep vegetables growing over the winter. And while a wooden greenhouse is lovely, you may wonder if it is the best material for a long-lasting plant home.
How long does a wooden greenhouse last? Wooden greenhouse structures are some of the sturdiest and longest lasting. Their lifespan, however, depends on the wood and climate. Pressure-treated cedar will extend its lifespan while living in a drier climate will reduce the moisture absorbed by the wood.
Wooden greenhouses are among the longest-lasting options, and truthfully, they are also some of the most customizable and beautiful. We love a good wooden greenhouse. So, that in mind, let’s talk about why we love them and what you can do to optimize the longevity of your investment.
Benefits of a Wooden Greenhouse
Obviously, one of the benefits of a well-built wooden greenhouse is that they are sturdy and long-lasting. But we also love them because they are beautiful and easy to customize.
There are a number of kits on the market. All you have to do is get the pieces for a greenhouse and assemble it for your plant babies. When you get a metal greenhouse frame, without specific tools and protection, you’re more or less locked into the delivered form.
When you get a wooden greenhouse kit, though, if you want to reshape it, cut it down, add on to it, you can easily. You’ll still require some skill at planning and care at making sure to seal it up.
If you are even more handy, planning out and building your own greenhouse from wood is a less expensive route to a gorgeous bespoke structure.
Speaking of which, let’s talk about the ways that you can make your greenhouse absolutely gorgeous. For starters, wooden structures look natural in a garden setting. They add to the romantic ambiance of a flower garden or a veggie patch.
It doesn’t have to be a large carpentry project. Even a nice little lean-to made of wood looks right at home. The size doesn’t matter a whole lot. Think about your needs. Consider the space of your garden. Then, build a greenhouse that matches your aesthetic.
With wood, you’ll be able to stain or paint it to your ideal look. You could even pair the wood frame with brick or stone around the foundation if it would better match your house. Who doesn’t love matching outbuildings?
Of the variety of constructions, a wooden structure is, of course, one of the heavier options. With a proper foundation, this makes it the sturdiest. If you’re in a windy area, sturdy and heavy is good. You definitely want something that will stand up to the weather.
Yes, aluminum frames can be sturdy. However, most of their strength is reliant on the windowpanes holding up. In a bad storm, should a glass pane break, it puts the rest of the structure at risk.
A wooden greenhouse, on the other hand, is built similarly to a home. Its frame is its strength. If a window breaks, the body will still stand. That’s one of the best things about wooden greenhouses.
Since you’re here asking about how long wooden greenhouses last, you should know that they last a long time. Some of our favorite gardeners have reported buying old homes with wooden greenhouses that were still standing despite years of neglect.
However, even if neglected, they’ll still stand strong. With love and time, you can revitalize an old greenhouse for future use.
Owners who’ve built their own have gotten 30 to 60 years of use out of their wooden greenhouses. It takes care to keep the structure in good repair to ensure longevity. With that, let’s talk about how to set your own wooden greenhouse up for a long life.
Best Wood for Wooden Greenhouse Construction
First things first, a good wooden greenhouse needs to be constructed of the right kind of wood. While it’s fine to do your interior woodworking projects with common pine, a greenhouse needs to withstand the elements.
The interior of a greenhouse gets very warm and humid. Wood exposed to moisture is likely to rot. You must also consider that exterior woods are at the mercy of the sun and bugs. What you want are rot-resistant, insect repelling building materials that can take sun exposure. Here’s what you need to know about your options.
Rot Resistant Woods
Let’s start with the woods that are naturally predisposed to rot resistance and insect repelling. Our favorite is cedar. It starts with a gorgeous red, and in the sun, fades to a silvery gray. It’s naturally moisture resistant and repels insects.
The other benefit is that it isn’t chemically treated. There’s no risk of a treatment vaporizing in the heat of the greenhouse and affecting your plants.
California redwood is another great option. It’s great in high moisture situations, having grown in foggy, humid conditions. It will still require a stain or paint to protect it from the sun. It has a beautiful natural grain, though, so you might consider a light stain.
In New England, black locust is a historical favorite for wooden outbuildings for its humidity resistance. You might consider this if you live in that area in order to use a locally sourced material that fits in with the scenery.
Pressure Treated Wood
The number one problem with non-chemically treated wood is that it’s expensive. So, to cut your own costs, you may consider pressure-treated wood. Now, that is going to come with its own potential issues. Organic farmers online frequently comment on how pressure treated wood leaks poison into their soil.
So, let’s look at some of the ways lumber for exterior builds is treated and what it might mean.
- Chromated Copper Arsenate (CCA). This was banned in 2003 for residential building due to the issue of arsenic contaminating the soil. That said, some lumber on the market may still be treated with this. Be sure to ask.
While arsenic in the soil is a big issue, the larger issue is that the humidity inside your greenhouse can vaporize the arsenic, making it airborne. The exposure to your plants and you is unhealthy at best and poisonous at worst.
To replace CCA, new(er) treatments, Alkaline Copper Quat (ACQ) and Copper Azole (CA-B), are used instead. These rely on higher percentages of copper to compensate for the lack of arsenic. Copper can also leach into the soil, but it does so in small quantities only a few inches out from the exposure. It’s not a high risk.
Best Treatments for Wooden Greenhouses
In terms of wood treatment itself, copper-based pressure treatments are the best option. We still love the look of natural wood, though. So, let’s transition into surface treatments for your wooden greenhouse. These options will protect your greenhouse. They will also give you a gorgeous finish and a unique look.
Before you do anything, paint, stain, or burn, you should use a wood preserver. The number one suggestion of organic farmers is linseed oil, which creates a great moisture barrier. It takes a while for it to dry, so be prepared to wait. Your patience will be rewarded.
Pine tar is another organic compound that you can use to prolong the life of your wood. On its own, it even has a nice tint to it that will replace stain. But the big story is that it was the compound used on Viking ships of old to make them seaworthy. It’s amazing at sealing out moisture.
After you’ve used your wood preserver, if you so choose, look at a good wood paint. Something like Thorndown’s if you’re in the UK, or Kilz if you’re in the US.
Your paint needs to serve to protect your wood against rot, sun, rain, and it’s best if it’s Eco-friendly so as not to leach bad things into your greenhouse.
You could consider using the same paint that you used on your house. It should serve just fine, and it has the added benefit of matching. Whatever you use, remember to refresh the paint every other year for ultimate protection.
If you love the grain of your chosen wood, a stain is a great option. This allows you to enjoy the natural beauty of your wooden greenhouse. Especially if you’re going for a natural look in your garden, this is a great option. You can customize the color to really show the grain while still being natural.
A stain absorbs deeper into the wood, depending on the porosity. Technically speaking, you don’t want your wood to be too porous at the time of staining. Use a wood preserver first or follow up with a glaze to make sure there’s a good moisture barrier.
Sho Shugi Bahn
The first time I learned about this wood preserving option was on a “tiny home” show. The concept is Japanese. What happens is:
- You use a blowtorch to blast the wood until the outer layer chars.
- A hard bristle brush can be used to reveal the grain.
- Finally, a natural oil is applied to finish the process out.
The result is a rot-proof, water-proof, pest-proof, and fireproof wood. In the end, the look is a blackened wood grain that is very striking. As with paint and stain, you will need to do some upkeep to maintain the look. It should last 50 years as long as it is oiled frequently enough.
Traditionally, Japanese cedar is used due to its innate ability to take the heat. With this option, it’s important to use the right kind of wood, as not all types will respond correctly. You should also remember to wear a mask while brushing it down to prevent inhaling dust.
Climate Control for Longevity
Once you’ve picked out your wood type and your favorite exterior treatment, it’s time to consider caring for the interior of your greenhouse. This is where all the magic happens, so let’s talk about optimizing it for plant care and overall longevity.
Should You Use a Climate Control System?
The temperature inside a greenhouse can fluctuate from 30º at night to over 100º in the dead of the afternoon on a temperate day. This can be mitigated by opening the vent windows and door during the day to improve airflow.
When it becomes cooler, you can use thermal mass heat sinks to keep your plant babies warm throughout the night.
However, in a larger greenhouse, or one in a particularly volatile climate, you may consider getting a climate control system in place. This will help to maintain a level temperature all day and night. It can also be used to control the level of humidity.
Too much humidity can be damaging to your wood and affect the longevity of the whole greenhouse. And honestly, depending on your plants, you probably don’t need tropical levels of humidity all the time, either.
Preventing Mold in a Wooden Greenhouse
Of all the things you were hoping to grow in your greenhouse, we bet mold wasn’t on your list. Frankly, mold is not a great thing for the health of your plants. It’s terrible for you as well if you intend to spend any time inside.
But since we’re talking about wooden greenhouse longevity, the important thing (for our purposes right now) is that mold is bad for your wood. The spores get into the pores of the wood and multiply. They eat through the wood fibers and compromise the integrity of the structure.
The best way to prevent mold is proper ventilation and humidity control. This can be done either with proper use of vent windows and doors or with a climate control unit.
If you see mold creeping up, a natural way to remove it is with a spritz of white vinegar or hydrogen peroxide. Using a 30% solution, spray it down and let it sit for 15 minutes in order to fully kill the spores.
When mold gets into your plants, unfortunately, the only thing you can do is remove them carefully to prevent further spread. You’ll have to burn them safely.
Best Window Material for a Wooden Greenhouse
There are a lot of options for the glazing of your coverings. Because wood is sturdy, it can stand up to the weight of glass panes, which are easily the most beautiful. The other best option is polycarbonate.
Why Glass Paning?
Glass looks fabulous, but it has a handful of other benefits, too. Of the options, it has the longest lifespan, which goes well with a long-lasting wooden greenhouse structure. The beauty is obviously quite important, but function is a large concern as well.
In terms of function, glass allows the most direct light and heat through. Single pane or double pane glass allows in the sunlight needed for photosynthesis. It’s more expensive, but there are double pane glasses with argon gas in the center to increase energy efficiency. This is great if you’re concerned about heat loss at night.
Yes, initially, glass is going to be more expensive. However, due to the long service life, the cost will balance out. Obviously, if you live in an area with frequent hail, this is probably not your best option, though. So, what is your alternative?
Polycarbonate can be corrugated or not. Either way, it is not clear like glass. Because of this, the light let in is diffused. This is pretty great for plants. You can also invest in double-paned polycarbonate. This will create insulation that reduces heat loss.
And obviously, shatter resistance makes a better option for areas where glass breakage is a risk. Additionally, it’s cheaper at the outset. You will probably be curious about longevity. There seems to be no end to the bias between glass lovers and polycarbonate proponents.
While many agree that glass is classically the best, many argue that polycarbonate is stronger, sturdier and lasts longer because it’s less likely to break.
Whether you choose glass or polycarbonate, there are tons of great reasons either way. Glass is beautiful and allows you to see inside your greenhouse from the outside. It’s long-lasting and natural-looking. On the other hand, polycarbonate is great for diffusing light, insulating your greenhouse, and may actually last longer. Both are great choices.
Is a Wooden Greenhouse the Best Option?
After getting through all the options that go into building an overall greenhouse, we need to come back to the question of wooden greenhouses and their longevity. Are wooden greenhouses really the best way to go?
We think so. A wooden greenhouse is not only a gorgeous option, but it will last you nearly a lifetime. With proper upkeep, you can enjoy the structural addition to your greenhouse every day of the year for years to come.