Pros and Cons of a Fiberglass or Wood Pergola

“I want zero maintenance.” If you wanted to know how many times I’ve heard these words in my career as a designer, I’d say to take the number of presents under a spoiled kid’s Christmas tree and multiply by five hundred. Sadly, zero maintenance doesn’t exist. You can, however, reduce maintenance needs by selecting the right materials.

fiberglass pergola virginia

I do a surprising amount of custom trellis and pergola design. The majority are built of wood, but I’ve worked with fiberglass on a couple of them. I also designed one that was built of AZEK composite lumber, but unless you have access to just a phenomenal carpenter, I wouldn’t go there. So what are the pros and cons of wood and fiberglass pergolas?

Wood Pergolas


  • Cost – pressure-treated is generally the least expensive, with a decent price bump for cedar.
  • Availability – you can find wood for sale locally, no matter where in the US you live.
  • Ease of use – If you have a carpenter, he or she has worked with wood before. Wood is easy to work with and it’s easy to fix minor mistakes.
  • Information – wood is a known quantity. There are span tables galore to tell you what you can do with it, and your local permit store will know what to make of a wood pergola.


  • Weight – Cedar is pretty light, but pressure-treated wood can be pretty heavy. Depending on the application, you’ll need to consider this when it comes to footers or deck attachment.
  • Span – Depending on what size boards you use, your span distance can be limited.
  • Movement – Pressure-treated wood left to the elements will always warp, check, crack, or move in some other (less than ideal) way. Cedar is more stable, but if you’re going to have overhangs or unsupported runs, you need to know how it will behave.
  • Upkeep – to keep wood looking its best, you’ll typically want to paint or stain it. There’s no such thing as a lifetime treatment.

Fiberglass Pergolas


  • Weight – Fiberglass pergolas are really light. The one we installed on a deck was attached to a plate that attached between the joists. Easy.
  • Upkeep – The vendor I used will ship your pergola painted in any color offered by Sherwin Williams or Benjamin Moore. The pieces get knocked around during shipping, so they include a couple gallons of touch-up paint. Since fiberglass doesn’t move like wood, you’re looking at years of life from a coat of paint.
  • Span – A fiberglass pergola can span almost 20 feet with no intermediate posts. That’s pretty great.
  • Installation – They ship from the factory as kits. End details are done, everything is cut to length, all you have to do is put it up and screw it together.


  • Cost – You’re looking at 2-3x the cost of wood for a fiberglass pergola.
  • Availability – there are only a handful of manufacturers, so odds are you’ll need to have the kit shipped to you. This also means that you need flawless drawings, because you’re getting what you asked for. Because it’s fiberglass, you’re stuck with what you get.
  • Lead time – Ordering in the spring or early summer? Prepare to wait. We were promised 3-4 weeks, which we promised the client. That grew to 5-6 weeks, then 10-12 weeks.
  • Installation – Yes, it’s a kit. That’s good. The down side is that it’s difficult to field modify the kit to account for bad measurements.

At the end of the day, you have to decide what’s right for you and where your priorities are. Cheap and easy? I’d go with pressure-treated lumber, and just design around the wood’s limitations. Moderately priced and cool looking? Cedar. Super low maintenance, or a big open space with no posts breaking it up? Fiberglass or another composite, just know it’ll cost you.

What to Look for in a Trellis

custom pressure treated trellises

The #1 most important thing? Scale. I hate to say it, but the majority of off-the-shelf trellises and arbors you can buy are woefully underscaled. Walk into your average big box store- or even many garden centers- and you’ll see sad, rickety little things made from such small pieces of softwood that they’re joined with staples. Staples!

The fact of the matter is that if you own a home in a populated, suburban area of northern Virginia, your home is probably fairly large for the size of your lot. In looking at the property, you’ll see a large (2000 sq ft+) home that may only have 5-10 feet of property to either side of the house. Proportionately, you’re skewed vertically. Tall is important, but you also need heft, beefiness, oomph. In the above photo (a landscape project in Bristow), my homeowners (who are on their way to becoming certified plant geeks, which I love) had the patio installed before I was part of the process. I was left with a narrow bed, right alongside a blank garage wall. Obviously we were going up and staying narrow, but we needed to offset the mass of the garage. What you see is a trellis made of pressure-treated 2×4 lumber, with climbing hydrangea growing on it. The homeowner built the trellis I designed, and he had the great idea to paint it black. The dark color adds to its visual weight and presence.

air conditioner screening trellis

Here’s another example. In this case (a landscape project in Aldie), the air conditioner was flanked on either side with shrubs that will screen it quite well, but our property lines were so tight that we had to take the path right up next to the unit. The trellis we built here is narrow, but made from 4×4 posts and 2×2 cross pieces.

This takes us to the other important consideration when buying or building a trellis: material. The least expensive route is pressure-treated lumber. Actually, the least expensive route is untreated lumber, but that would be a tremendous mistake unless you wanted a disposable piece. Pressure treated lumber’s price is an advantage, but its use carries some risks. It’s much more likely to warp, twist, check, or move in a way you won’t want it to. You can see that in both of the examples above, the trellises are made of straight pieces of lumber butted up against one another. The thinner you make a piece of pressure-treated lumber, the more likely it is to move or crack.

Another issue with pressure-treated lumber is that what you buy at the store today- especially the big box home improvement store- is pretty green and wet. You have to allow it to dry out for several weeks before you can stain or paint it.

An excellent choice for building trellises is western red cedar. It’s a durable wood that tolerates exposure to the elements, and it’s much more stable than typical pressure-treated lumber. It’s also much lighter. I built a gate for my house out of pressure-treated lumber last year, and I’ve regretted it every day. This spring I will likely replace it with one made of cedar. Knowing what I know, why didn’t I do that the first time? Cedar is significantly more expensive than pressure-treated lumber. I made a lot of improvements to my landscape last spring and like everyone else, I had a budget. Don’t worry, the wood will get rolled into another project.

What about composite lumber, like Trex, Evergrain, AZEK, or the like? The problem with these choices is that they aren’t inherently structural. They’re not stiff and they’ll sag if not properly supported. So you can build a trellis with pressure-treated lumber for the framing and clad it with composites if you want to create a low-maintenance feature. Just be prepared for the cost- composite lumber is often 2-3 times the cost of pressure-treated lumber.

Trellises are incredibly versatile components of a landscape. They’re great as stand-alone art pieces, but they can serve a variety of functions: screening utility equipment or unwanted views, framing a desirable view, adding a little privacy, or just providing a place to grow a beautiful climber like honeysuckle or clematis. Take a look at what’s out there, but look at it critically and put in something better.