“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.
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?
- 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.
- 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.