Both make a good pergola, and they are very different to own. One is lumber that is cut and fitted in your yard, and it keeps moving a little with the weather. The other is a metal frame with a baked-on color that stays as it is.
This guide compares them for the weather we have: humid summers, strong sun and thunderstorms. We build both, so we have no side to take.
Swipe the drawing sideways to see all of it.
Three materials, not two
Pressure-treated pine. Pressure-treated southern yellow pine is the common pergola wood in the Carolinas. The posts are rated for ground contact. It arrives wet. As it dries it shrinks and shows small cracks along the grain, called checks. That is normal and not a defect.
Cedar. Cedar is lighter and more stable, and it resists rot naturally. It costs more than pine. Left bare, it turns silver gray.
Aluminum. A powder-coated aluminum frame comes from a manufacturer's system. It does not rot or warp, and the color is baked on, so there is nothing to stain.
The service pages show how each is built: wood pergolas and aluminum pergolas.
Humidity, sun and summer storms
Humidity and rain. Water is what ends a wood pergola, and it gets in through the end grain: the bottom of a post and the top of a beam or rafter. The most common problem is a rotten post base, where water sits at the bottom of the post. Two details answer it: a post base that holds the wood off the concrete, and a cap or a slope on top. Aluminum has no grain and does not rot.
Sun. Sun and rain wear the finish on wood, which is why wood needs stain or sealer again over the years. Cedar that is not sealed turns silver gray. On aluminum the color is baked on, and it needs no stain.
Summer storms. An open frame lets wind pass, in wood and in aluminum alike. A storm can drop a limb on either one. On a wood pergola a split rafter or a broken beam is replaced board by board, and the sound parts stay. On an aluminum frame the damaged part is replaced with a matching part from the same system.
Upkeep over the years
| Question | Pressure-treated pine | Cedar | Aluminum |
|---|---|---|---|
| Rot | Treated against it. Watch the post bottoms. | Resists it naturally. Same weak points. | Does not rot |
| The first months | Dries, shrinks and shows small checks | More stable | No change |
| Stain or sealer | After it dries, then again over the years | Sealed to keep its color, or left to turn gray | None |
| Color | The stain you choose | Its own color, or a stain | Fixed colors. Black, white and bronze are common. |
| Price | Quoted after we see photos | Costs more than pine | Quoted after we see photos |
New pressure-treated wood should dry before stain or sealer goes on. That can take weeks to a few months, depending on the weather. The written quote says if stain or sealer is included in a pergola we build.
If you choose wood, plan for stain or sealer as part of owning it. If that sounds like a job you will never do, that is a fair reason to choose aluminum.
Look and size
Wood has thick parts and a built-by-hand look: typical 6x6 posts, doubled beams, notched rafters with shaped tails, knee braces and trim at the post base. It is cut on site, so it is sized to your patio or yard, not to a kit size.
Aluminum has slim parts and straight modern lines. It comes in the sizes and the fixed colors its system offers. Black, white and bronze are the common colors.
One more voice may decide the look for you. Many HOAs must approve the material and the color before work starts. Read HOA pergola approval before you set your heart on one.
Shade options
The material does not change the basic fact. An open pergola gives partial shade that moves with the sun. What changes is how you add more.
- Wood. The rafters are chosen board by board. Typical rafters are 2x6 or 2x8, every 12 to 24 inches, and 2x2 top slats can run across them when more shade is wanted.
- Aluminum. The system sets the sizes and the spacing. If you want a louvered roof that opens and closes, tell us, and the quote says if we can supply it.
For the numbers behind rafter size and spacing, see how much shade a pergola gives.
The ground, the house and repairs
The ground. Both need something solid under every post. Wood posts stand on concrete footings, or on steel post bases anchored to a concrete slab that is thick and sound enough. An aluminum frame is anchored to a sound slab or to new footings. Loose pavers cannot hold a post of either kind.
The house. A wood pergola can attach to the house on a ledger board that is bolted to the house frame, with flashing above it. For aluminum, the manufacturer has the final word on how its frame meets a wall, and the written quote says how yours would be fixed. Either one can stand on its own posts next to the house. See attached vs freestanding.
Repairs. Wood can be repaired piece by piece. If the posts and beams are sound, the bad parts are replaced and the good ones stay. That is how our pergola repair works.
How to choose
- Choose pressure-treated pine if you want the classic wood look and a frame cut to your patio, and you accept small checks in the wood and stain or sealer over the years.
- Choose cedar if you want wood that is more stable and resists rot naturally, and the higher cost is fine with you.
- Choose aluminum if you want the least upkeep and a clean modern look, and one of the fixed colors suits your house.
- Skip wood if you know you will never stain or seal it and you want it to look new.
- Skip aluminum if you want thick timber parts, a stain color of your own or a shape outside what a system offers.
Not sure yet? Send photos of the patio or yard and the rough width and depth, and say that you are deciding between the two. Send them on the photo quote page for a free written quote.