How to Build a Wooden Pergola in Your Garden

Building a pergola can be a daunting task for a homeowner, with a suite of potential issues. In this guide from The Porch Specialist, we’ll take you through a step-by-step guide to building one of our wooden pergola kits in your garden, leaving you with a strong, sturdy installation. 

A pergola is a great method of home improvement, creating a beautiful outdoor living space within your garden for entertaining, relaxation, or even work. The Porch Specialist offers bespoke pergola kits, designed around the needs of your outdoor spaces. 

We’ll look at installing a freestanding pergola, then cover how to install a pergola on both a patio and on decking.

Before You Start

Before you start, it’s important to establish whether you will need planning permission to build a pergola in your garden. A wooden pergola should fit within the boundaries of permitted development. 

However, there are instances, such as if you live in a listed building or in an Area of Outstanding Natural Beauty, where you may require planning permission. If you have any doubts, contact your local housing authority to make an inquiry.

How to Build a Freestanding Pergola

Our pergola kits are designed for easy installation, coming with instructions laying out all distances between posts, beams, and joists. 

When installing your freestanding pergola you must first mark out the distances between posts on the ground. Our pergola kits come with a choice of staddle stones or wood in a concrete footing. But for this guide, we’ll focus on concrete, which will provide a solid installation anywhere in your garden. We’ll be showing you how to install a traditional four-post square pergola, but larger pergolas are also available.

Step 1

First, you must dig holes for each post. Post holes should be between 70 and 120 cm in depth. The holes should be slightly wider than your posts, to allow for the concrete to be poured around them. Make sure each hole is the same depth, before adding 10 cm of gravel to the bottom of each of your four holes. Measure your holes again to ensure that they are the same depth. 

Step 2

Insert your poles, using a spirit gauge to make sure that they are level. You should also ensure that they are correctly positioned to connect to the other poles and that the beams and joists can be accurately connected. 

Step 3

Once your post is correctly positioned, you’ll need to nail smaller planks to the bottom of your post to brace it in place. Angle these planks so they are wedged against the ground. You can use scrap wood for these planks, and once your post is secured you can stop holding it in place.

Step 4

Once all four of your posts are correctly positioned, level with one another, and braced with support planks, you’ll need to mix concrete to fill the holes around them. Securing the posts in concrete will ensure a sturdy pergola build. 

Mix the concrete according to the instructions, and pour it into the holes, leaving a small gap at the top to avoid overspill. You’ll need to stir the concrete around each post before it dries to aerate it, removing air bubbles. Leave the concrete to dry for a day, then remove all the bracings.

Step 5

You’ll first need to secure the beams, which will rest on top of each post. These will need to be affixed with wood screws to secure them in place. Our kits come with angled braces between posts and beams. In a four-post kit, there will be two main joists, which will need to be fitted across beams on top of posts and secured.

There will also be angled braces attached between posts and these larger joists. Once these are all secured, there are a series of smaller joists to be placed along the beams at designated intervals. Each kit we sell is designed around your specifications, with things like the height of posts, the number of joists, and your pergolas length tailored uniquely for you.

How to Build a Pergola on Decking

A regular pergola can comfortably be built over an existing deck. To do so, the bases of each post must be securely fastened to the base using post bases, sometimes called post supports. 

These post supports are drilled into the decking, creating a secure base into which the posts can be inserted and secured with screws. If using post bases, ensure you buy ones that are suited to the size of post you are using, and that it is strong enough to support your pergola. 

The rest of the building process will be identical, giving you a stunning pergola on top of your decking.

How to Build a Pergola on a Patio

Depending on the type of patio you have there may be different installation methods. If you have a solid concrete patio, you can install a garden pergola using post bases. You’ll need to drill into the concrete, and use anchor bolts to attach the post bases. Anchor bolts expand to give you a strong seal within the concrete, firmly holding your pergola posts in place. 

If your patio is made from tiles, you can remove the tiles where the posts will sit, and install the posts the same way you would over grass, digging holes and supporting them with concrete. Once you’ve measured the space required, you can cut your removed patio slabs to size to fit into the gaps around posts. This way you’ll have a secure pergola over your tiled patio.