Concrete and In Ground Pergola Post Guide

If you’re shopping for and comparing wood pergola kits, this pergola post information will come in handy since post length and pergola height is one of the important decisions you’ll make! What are the important factors when considering pergola posts? The length of the post and how you’re planning to install the posts are top factors to review when making your pergola installation plan to ensure structural integrity of the pergola structure. Since the posts are the legs for your pergola, it’s important to review size and installation method for your wood pergola posts to ensure that your pergola is level and well anchored.

Other factors to review that can help make your outdoor pergola perfect for your space include pergola wood type and pergola dimensions. To make to most out of your outdoor area, take a minute and see what options work for your specific needs. Will the best choice be a freestanding structure or one that is attached to a wall? If you’re not quite sure, take a few rough measurements and then you can compare pergola styles. Once you’ve determined the general style you’d like, you can choose your desired post length and how you’ll install your pergola. Call us or start shopping today to get the perfect pergola kit for your project!

Pergola Post Information: Pergola Post Length

For our full size wood pergola kit styles, we offer posts with standard lengths of 8 feet, 10 feet and 12 feet. These styles include Big Kahuna, Big Kahuna Timber Frame, Big Kahuna PLUS, Sombrero, Melbourne, and Fedora pergola kits. When trying to decide the length of pergola posts needed for your wood pergola kit, there are a few things to consider. How tall do you want your pergola to be? If you have space constraints such as other nearby structures, trees or other vegetation, you’ll want to review that before selecting the post height. The method you’ll use to install the posts also should be factored in to your post height selection. There’s more info below about different post mounting methods to consider. Lastly, how much space do you want underneath your pergola? Will you add and outdoor kitchen or dining area that requires a certain amount of headroom above the accessories? Your beam clearance or desired height above the ground also correlates to which pergola post length you’ll select.

What is the Desired Pergola Beam Clearance?

Pergola beam clearance, or the height to the bottom of the beam (low point of the roof structure) varies based on the pergola kit style you select. Refer to the Pergola Height Calculations chart below to view the approximate height and beam clearance measurements for your desired pergola kit style. These measurements are approximate and can vary slightly based on wood type. Here is some helpful information explaining the calculation for the height to the bottom of the beam for our various pergola styles.

Beam Clearance for Big Kahuna, Sombrero, and Melbourne pergolas: approximately 7 inches less than the length of the post that is above ground level, for example it would be 7 feet 5 inches for an 8-foot post (7’6″ if using post mounting hardware) or 9 feet 5 inches for a 10-foot post (9’6″ if using post mounting hardware).

Beam Clearance for Fedora: approximately 14 inches less than the length of the post that is above ground level, for example it would be 8’10” for a 10′ post (8’11” if using post mounting hardware). The Fedora height is different than our other standard full size kits due to the un-notched rafter design. The Fedora pergola kits include black powder coated angle brackets that add an extra level of stability and charm. Included in each kit, these versatile L-shaped angle brackets join the rafters to the beam to create a secure connection that adds an extra level of structural stability to one of our most popular backyard pergola kit designs.

Beam Clearance for Big Kahuna Timber Frame Pergola Kits: the overall height and beam clearance for our timber frame pergola kits are slightly different than the standard Big Kahuna pergola kit. Beam clearance is approximately 7 feet 9 inches for an 8-foot post (if using post mounting hardware) or 9 feet 9 inches for a 10-foot post (if using post mounting hardware).  

Beam Clearance for Big Kahuna PLUS covered pergola kits: our covered roof pergolas are engineered with a minimally sloped metal roof (1/2” to 12”) to create a versatile outdoor roofed structure. To achieve the proper roofing slope and ensure rafters will fit square over the beams, you must ensure the proper post placement and post height differential. For our freestanding covered pergola kits, this results in selecting either a combination of 8′ and 10′ posts, 10′ and 12′ posts (for installation on slab or footer); or (2) 12′ posts (for in ground installation), which will result in a varied beam clearance depending on your selection.

How Tall Do you Want Your Pergola?

It’s a matter of choice, but you probably don’t want to make the pergola too tall. For the Big Kahuna, Big Kahuna Timber Frame, Sombrero, and Melbourne, 8 or 10-foot posts suit most situations unless you’re installing your posts more than 2′ in the ground.

For the Fedora, we recommend 10′ posts on a slab or footer and 12′ posts (or longer) if going in the ground. Smaller kits generally look better with a shorter post.  But, keep in mind things like ceiling fans or other accessories, head room for tall people, standing up in a hot tub or dancing on tables! For our Brim trellis pergola kits, we offer 10′ posts or 12′ posts for mounting the ground.  

What is the Desired Overall Height for Your Pergola?

Pergola overall height, or the height to the top of the top slats (high point of the roof structure) varies based on the pergola kit style you select. Refer to the Pergola Height Calculations chart below to view the approximate overall height measurements for your desired pergola kit style. These measurements are approximate and can vary slightly based on wood type. Here is some helpful information explaining the calculation for the overall height for our various pergola styles.

How Will You Install Your Pergola Posts?

Other important factors when choosing post height and determining desired overall pergola height is your post installation method. Will you be installing your posts either buried in a concrete footer, or installing on top of a concrete footer or existing concrete slab? If installing your posts buried in a concrete footer, then you will need to add the length of the post below the ground to the desired height of the posts.

How Deep Should the Posts be Installed for Frost Line?

To determine the length below ground, we recommend at least 2 feet or more depending upon the frost line and building codes in your area. Do you live in a northern state where the ground is frozen for certain months out of the year, or a southern state where the ground does not freeze? If you live where the ground freezes you will want to be sure that you set your posts or footings deeper than the frost line. This will ensure that frost heave will not pop your pergola out of the ground like a cork.

The correct depth can be determined by checking with your local building code department or online resource. In warmer climates you may be able to use 10′ posts, which would be buried 2′ in the ground, and colder climates will most likely use 12′ posts which would be buried 3-4′ in the ground.

Pergola Height Calculations

As you’re measuring your space for your pergola, refer to this chart to determine your pergola post height. These measurements are approximate and can vary slightly based on wood type.

Pergola Style	Overall Height (Approximate) – 8’ posts	Beam Clearance (Approximate) – 8’ posts	Overall Height (Approximate) – 10’ posts	Beam Clearance (Approximate) – 10’ posts	Overall Height (Approximate) – 12’ posts	Beam Clearance (Approximate) – 12’ posts
Big Kahuna Pergola Kit	8’6”	7’6”	10’6”	9’6”	12’6”	11’6”
Sombrero Pergola Kit	8’6”	7’6”	10’6”	9’6”	12’6”	11’6”
Melbourne Pergola Kit	8’4-1/2”	7’6”	10’4-1/2”	9’6”	12’4-1/2”	11’6”
Fedora Pergola Kit	n/a	n/a	10’2-1/2”	8’11”	12’2-1/2”	10’11”
Big Kahuna Timber Frame Pergola Kit	8’7-1/2”	7’9”	10’7-1/2”	9’9”	12’7-1/2”	11’9”

Interested in a pergola style you don’t see here? View all pergola kits for a comparison of styles.

 

Pergola Post Installation

Mounted on Concrete Footer or Existing Slab

The easiest method of installation is to dig footings to the correct depth (below the frost line in your area) and use post mounting hardware to attach the posts to the concrete footings or existing concrete slab as follows: Order the 8 foot or 10 foot post option and add the post attachment hardware to your order.

This will connect the pergola posts to the footings or slab, and also hold the bottom of the post up 1″ from the concrete surface to keep the bottom of the posts out of water that may accumulate on the patio.

For our Big Kahuna, Sombrero, Melbourne, and Fedora pergolas, when you select the option for posts on concrete slab or footer (rather than posts in ground), the post base mounting hardware will be included with your kit. The post base you receive will vary based on the wood type you select – either ABU66Z for #1 pressure treated southern yellow pine or ABU66RZ for rough sawn western red cedar.

When you add your pergola kit to the cart, if you selected Post Will Be Going “On concrete slab or footer (10′ posts with mounting hardware)” or “On concrete slab or footer (8′ posts with mounting hardware)”, the hardware has already been added to your kit. If you made any other selection and you’d like to purchase mounting hardware, contact us and we can adjust your order to include post mounting hardware.

Other Pergola Mounting Surfaces

With deck pergola kits, we advise that if you’re mounting the pergola on to an existing deck, it’s best to pour footers below the deck and mount posts to the footer. Or, build the pergola posts into the framing underneath the deck (pull the deck boards in the location where you want your posts to land and mount posts into the framing of the deck).

If you prefer to install your pergola without a concrete slab foundation, you’ll need to dig post holes for concrete footings. These footings are especially useful if installing over an existing paver patio. With pergola kits on paver patios, we advise removing the pavers rather than installing on top of the paver. Ensure that the footings are sized according to your pergola’s dimensions and post locations. Make sure if you will be setting the posts on top of footings, that the footings are dug below the frostline (if there is a frost line in your area).

In Ground (buried in concrete footer) Installation

If you will be sinking your posts into the ground (buried in a concrete footer) you have two different options on how to pour the concrete around the posts:

Option #1 – Not flared bottom: Works in warm climates where the ground does not freeze.

Option #2 – Flared bottom: For climates where the ground freezes. When the concrete is set below the frost line and flared on the sides this prevents the frozen ground that will be pushing on the sides of the concrete from popping it out of the ground. Also the use of concrete form tubes helps this because the smooth surface of the tube will not allow the ground to grab the concrete and pull it up. We also recommend if you are putting the pergola posts in ground, that you wrap the bottom part of the post that will be in contact with cement in a peel and stick roofing membrane. These pergola installation accessories can be purchased at your local hardware store.

If you follow these suggestions, you are sure to have a pergola that will stay put where it was intended to be for the life span of the lumber. Take a shortcut and you’re bound to have a pergola that is out of level. Frost heave can push posts out of the ground 3″ or more if not installed properly.