Aside from using high-quality materials, choosing an appropriate mounting method is crucial to ensuring your pergola will stand the test of time.
Exploring the different types of anchoring methods will help you decide which option works best for you.
So, how are pergolas anchored? Continue reading this article to explore different pergola mounting options.
Typically, pergolas are anchored by setting the posts on footings.
The footings can either be installed in a concrete base deep in the ground or above ground level. The latter method attaches the posts to metal brackets embedded in cement.
Another less traditional method to anchor the pergola posts is to set in a heavy steel footing directly in the ground—without the need for concrete or digging—and attach the posts to a saddle structure at the top of the steel footings.
Let’s go deeper into the different types of pergola footings and how are pergolas anchored:
These types of anchoring methods mainly require digging a deep enough hole to hold the posts. Then, a layer of concrete is poured to hold the pergola.
The concrete filling can take various shapes, like a flat slab or a pyramid footing with a set-in hole for the posts—this method is for directly inserting the posts into the concrete.
Alternatively, you can pour the concrete into tubes and install a metal anchor in the concrete pillar to hold the posts above the ground.
You can also just install the pergola posts directly into the ground without the use of cement.
Here’s how each anchoring method is done:
The first step in installing the pergola, whether you’ve decided to anchor it using cement or not, is to mark the post holes.
Typically, you’ll want to choose a location that’s suitable for digging and mounting the pergola footings.
Building the pergola on a paved patio, especially a paving stone patio, can be a bit troublesome, usually because this type of flooring requires removing the stones before digging.
Fastening the posts directly on the paving stones won’t give enough support to the structure and might risk blowing the pergola away when it’s subjected to harsh environmental conditions.
You should also contact your local code compliance office or call 811 before digging. This is to make sure there aren’t any underground utilities in the area you’ve marked for the post-holes.
Once you’ve picked an appropriate location, you can start digging the holes for the footings.
Generally, each hole would have a diameter between 12 to 24 inches, depending on how large the concrete footing or the metal bracket is. The depth is usually one-third the height of the posts—at least 12 inches deep—but that may differ according to the local building codes.
Expansive soil types like clay and freezing climate also determine the footing depth. For these types of conditions, you should drill down beyond the ground freezing—about 48 inches deep—to allow room for expansion, ensuring the pergola posts don’t heave.
Preparing the concrete is usually a simple task. All you need to do is follow the package instructions. Whether you’re using regular or fast-setting concrete, you should make sure of the following:
- Avoid adding too much water, as that makes the concrete lose its strength and won’t cure properly.
- Make sure you don’t have any pockets of dry mix remaining to avoid having an under-mixed concrete that crumbles once it dries.
This step is adjustable depending on the method you choose to anchor the posts.
This type of method requires you to fill the bottom of the hole for around 4-6 inches to make the base where the posts will set in.
Once the base is done, place the post in the hole and make sure it’s completely vertical without any angles. You can use a level to ensure the posts are plumb.
After vertically aligning the posts, fill the rest of the hole with concrete and continue checking using the level to confirm the posts don’t tilt.
Although this option results in sturdy posts, it has some limitations, including:
- It can be tricky to have perfectly vertical posts, especially if the base of the hole isn’t plumb.
- The concrete doesn’t protect the wood from rot because as the concrete dries, it can shrink slightly, leaving a small gap that traps rainwater and holds up moisture. That creates a perfect environment for fungal growth, eventually rotting the wood.
Instead of directly anchoring the posts into the concrete, you can attach the posts to a metal anchor inserted into the concrete pillar. That way, you’ll keep the posts away from the wet soil, reducing the moisture surrounding it and; thus, the risk of rotting.
Plus, it makes future repairs much easier, since the posts are anchored above the ground. That said, the metal anchors can still rust and wear over time.
Here’s how to install a metal saddle into the concrete pillar:
- Place a Sonotube into the footing holes
- Fill the tubes with concrete
- Set the metal saddle into the concrete before it sets up.
Directly installing the posts into the ground is a much simpler option that doesn’t require the use of concrete. However, make sure that the lumbar used is pressure-treated and ground contact approved.
All you need to do is drop the posts into the hole, level them, and fill back the soil while ensuring the posts are plumb.
All the previous anchoring methods require effort for digging. Not to mention, it’s time-consuming—especially if you’re using regular concrete that takes up to 48 hours to dry.
Luckily, you can use a helical pile with a metal saddle attached to its top as the pergola footing.
The helical pile usually has an auger attachment to drill deep into the ground. Then, the anchor is screwed to the top of the pile to hold the pergola posts.
No, not all pergola anchoring methods require cement. You can use pressure-treated wood to install the pergola directly into the ground or use helical piles as footings to anchor the pergola.
Plus, mounting pergolas to deck surfaces doesn’t require digging or cement. Instead, it uses metal brackets to anchor the posts to wood surfaces.
Generally, most pergolas are anchored securely to the ground to ensure safety. Even free-standing cantilevered pergolas have two posts secured to the ground.
That said, some pergolas are wall mounted and depend on the wall for support; instead of the ground.
Yes, harsh weather conditions can blow away ground-secured pergolas. However, that depends on the materials and design of the pergola and the wind speed.
Heavy-duty pergolas can withstand wind speeds of around 30 to 80 miles per hour; stronger than that might risk blowing away your pergola.
So, how are pergolas anchored?
There are two main options to secure pergolas. The first method requires excavating holes and either placing the posts into the ground using cement only, or concrete with metal saddles to anchor the posts.
The other option is to use helical piles with metal anchors at the top of it to secure the pergola. You can also mount pergolas on wooden decks using metal brackets.
Whichever method you choose, make sure to check the soil type and local guidelines to determine whether the anchoring method is suitable for the desired location or not.
Ben has a bachelor’s degree in construction engineering. When not constructing or remodeling X-Ray Rooms, Cardiovascular Labs, and Pharmacies, you can find him at home with wife and two daughters. Outside of family, He loves grilling and barbequing on his Big Green Egg and Blackstone Griddle, as well as working on projects around the house.
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