How to Build a Pergola: A Step-by-Step Beginner’s Guide

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Looking to build a pergola for the first time? 

Worried about choosing the right setup or getting your measurements wrong?

Then you’re in the right place! 

In this blog, we’ll guide you through each step of building your pergola, from foundations and setting the posts to constructing the frame and treating the wood. So no matter if you’re a complete beginner or a seasoned pro, we’ll help you set up a beautiful pergola for your new outdoor dining space, garden feature, or relaxation area.

Let’s jump in.

What is a pergola?

A pergola is a wooden structure made up of vertical posts and slatted timber roofs that can be freestanding or against your house. They tend to be a square or rectangular structure that stands above a section of your garden. 

Why choose a pergola?

Pergolas can make a statement in your garden. They can frame outdoor seating areas, dining tables, hot tubs,entrance ways, and more.

Due to their open structure, you can also use pergolas as a post for your climbing plants, like Wisteria and Ivy. Pergolas further add height and depth to your outdoor space and can be used to create a more secluded section in your garden.

There are also a number of customisation options for pergolas. You can: 

• Paint the wood with Johnstone’s Shed and Fence treatment and choose between brown or green to create the perfect look.
• Treat the wood with Ronseal FenceLife Plus to enhance its natural capabilities and keep your pergola looking fresher for longer.
• Hang lighting from the roof slats to add more ambience to your outdoor space. 
• Attach outdoor curtains or add a lattice wall to create more privacy.

Pergolas make a brilliant addition to your garden, due to the vast amount of customisation options you have. Once your pergola is up, you can adapt your space with the seasons or keep leveling it up with a fresh coat of paint and new decorations. 

How to plan for your pergola

Before you pick up your tools, it’s important to create a plan for your pergola build. This is an essential step that will ensure your pergola will stand the test of time. 

Here’s what you need to think about: 

Choosing the best location

• Sunlight: Do you want full sun, partial shade, or evening shade over your pergola? It’s important to think about the times of day you’ll be using it the most. 
• Purpose: Do you want to cover a seating area, walkway, hot tub, or dress the pergola with plants?
• Ground type: What type of ground are you building your pergola on? Is it soil, grass, patio, or decking? This will impact how to secure your pergola into the ground and may mean you need different materials or tools. 
• Space around it: Is there enough room left surrounding your pergola so you can easily walk around it? Is the space comfortable to use?

Pergola size guide (width, height, and spacing)

A pergola should feel proportional to your garden and the area it’s covering.

• Height: Usually around 2.1m–2.7m.
• Post spacing: Often 1.8m–3m, depending on design and timber thickness.
• Width/length: Based on the area you want to cover.

If you’re building over a patio table, measure the table and chairs and add extra space around it so it doesn’t feel cramped.

It’s important to note that dimensions will vary depending on your garden and the space you’re wanting to create. If you’re feeling unsure and looking for some extra advice, please get in touch with our friendly team.

Checking ground conditions (soil, patio, decking)

The surface you’re building on matters a lot:

• Underground cables and drains: Before digging into the ground it’s important for you to know where underground cables and drains are to avoid damaging them.
• Soil/grass: You can set posts into concrete in post holes for stability.
• Patio/concrete: You’ll likely need to bolt-down post bases into the harder ground to ensure stability.
• Decking: You may need to reinforce underneath so it can handle the weight.

Does your pergola need planning permission?

In many cases, pergolas don’t require planning permission, but rules vary depending on height, location, and whether it’s attached to a building. 

We recommend always checking local regulations if you’re unsure. Especially if you live in a listed building or conservation area.

Tools and materials you’ll need

Here’s what you’ll typically need for building a pergola.

Essential tools checklist:

• Tape measure
• Spirit level (a long one if possible)
• String line and stakes
• Pencil/marker
• Spade or post hole digger (for soil installs)
• Drill and drill bits
• Saw (if you’re cutting the timber yourself)
• Socket wrench/spanner set
• Ladder or step platform
• Safety gloves and goggles
• Timber and fixings checklist

Materials vary depending on design, but commonly include:

• Timber posts (uprights)
• Beams (main horizontal supports)
• Rafters (top slats)
• Braces (optional but recommended for stability)
• Exterior-grade screws/bolts
• Post bases or anchors
• Concrete (if setting your posts into the ground)
• Wood treatment/preservative

Step-by-Step guide to building a pergola

Now it’s time to get started on building your pergola. 

Here is a handy step-by-step process:

Step 1 — Measure and mark out your pergola area

Start by measuring the area where the pergola will sit.

Use stakes and string lines to mark out the footprint. This helps you to see the size visually before committing, keep everything straight, and confirm you’re happy with the placement.

Pro tip: Measure diagonally from corner to corner. If both diagonal measurements match, your layout is square.

Step 2 — Mark post positions accurately

Your posts are the foundation of your pergola, so placement matters.

Mark each post location clearly. Double-check that your spacing is equal where needed and the posts align with your string lines. 

You’ll also need to check that your pergola is not blocking any doors, paths or access to other parts of your property.

Step 3 — Dig post holes or prep your fixing points

Step 3 will vary depending on the surface you are building your pergola off.

If building on soil or grass:

Dig post holes (often around 600mm deep, depending on height and conditions) and make sure the holes are wide enough for concrete around the post.

If building on patio or concrete:

Use bolt-down post bases and drill into the surface using the appropriate masonry bits. Make sure to use strong anchors designed for outdoor loads; this will help keep your pergola stable.

Step 4 — Set the posts (and check they’re level)

If setting posts into concrete, you’ll need to: 

• Place the post in the hole
• Use a spirit level to check it’s vertical on all sides
• Brace the post temporarily (scrap wood works well)
• Pour concrete around it, we recommend using our Post Mix
• Check the level again before the concrete sets
• Repeat for each post. Let the concrete cure fully before adding weight. 

If using post bases:

• Fix the bases first
• Attach posts and check alignment/level
• Tighten fixings securely

Step 5 — Attach the beams and build the frame

Once your posts are solid and upright, you can attach the main beams.

This is usually a two-person job, so it’s worth asking for an extra hand throughout this step.

Steps:

• Lift the beams into position
• Clamp them temporarily if possible
• Check everything is level before fully securing it
• Bolt or screw beams into posts using exterior-grade fixings. We recommend using the Bolt Down Post Support for extra security.

Pro tip: Work slowly and measure as you go. Small errors here can become big problems later!

Step 6 — Add rafters and cross supports

Now your pergola is starting to come together. It’s time to get started on the finishing touches and add the rafters across the top beams.

They need to be: 

• Evenly spaced for a clean look
• Decorative (with shaped ends)
• Used to create more shade depending on spacing

To install:

• Mark your spacing along the beams
• Fix rafters in place one by one
• Keep checking alignment to ensure they are uniform
• Optional (but recommended): add corner braces for stability, especially if your pergola is tall or exposed to wind.

Step 7 — Secure Everything and Check Stability

Now that your finishing touches have been added, it’s time to check everything is secure and make sure your pergola is stable. 

Final Checklist: 

• Are all bolts/screws tight?
• Is anything loose or wobbly?
• Are the beams level?
• Are posts still vertical?

If you notice movement, add braces or reinforce fixings now — it’s easier than fixing it later.

Step 8 — Sand, treat, and finish your pergola

Your timber pergola needs to be protected to ensure it lasts a long time. Even if the wood looks great untreated, weather conditions can encourage your timber to rot and deteriorate over time. 

Finish options include:

• Exterior wood preservative
• Stain for colour
• Paint for a more modern look
• Clear sealant for a natural finish

If you want climbing plants, you can also add:

• Trellis panel
• Wire supports
• Hanging hooks for planters or lights

Common mistakes to avoid

If this is the first time you’re building a pergola, it’s normal to make a couple of mistakes. 

Here are a few of the most common mistakes and how you can avoid them:

1. Not measuring properly

Rushing the layout stage can lead to:

• Uneven spacing
• Crooked beams
• A frame that doesn’t sit square

Fix: Measure twice, check diagonals, and use string lines.

2. Posts not level

If your posts lean even slightly, it’ll throw the whole structure off.

Fix: Use a spirit level and brace posts while setting.

3. Using the wrong fixings

If you use screws meant for the indoors, you’ll be sure to see rust appear. 

Fix: Use exterior-grade fixings and correct anchors for the surface. We recommend using the Thunderbolt screws for extra stability.

4. Skipping wood treatment

This shortens the lifespan of the pergola drastically and will lead to your wood rotting. 

Fix: Treat timber before or immediately after installation. The sooner this is done, the less likely your pergola is to deteriorate in the British weather.

5. Not accounting for wind and stability

Due to their height, your pergolas are more likely to be susceptible to wind damage. 

Fix: Add corner braces and ensure posts are anchored properly.

Common questions about building a pergola

The cost to build a pergola ultimately depends on where you source your materials, tools, and the size of your project. 

When it comes to budget, you generally need to consider the cost of:

• Timber (posts, beams, rafters)
• Fixings and brackets
• Concrete or post bases
• Wood treatments, stains or paints
• Tools (if you don’t already own them)

A pergola kit can sometimes be more cost-effective than buying individual timber pieces and will also save you time sourcing all the separate materials. 

The Pergola Kit

To make your pergola build even easier, we have put together the Pergola Kit. This handy kit is designed to give you everything you need to build the perfect pergola for your outdoor space. 

It includes: 

• Sawn and treated timber
• Timber posts
• Wafer head screws

The timber is C16/C24 grade, which is a superior quality wood that ensures your pergola has strong foundations. 

Our kit comes in three different sizes, including: 

• 2.4m x 2.4m Pergola
• 3m x 3m Pergola
• 3.6m x 3.6x Pergola

Our pergola kit is suitable for DIYers with any level of experience and allows you to build a pergola in half the time it would normally take. 

Questions about building a Pergola

What’s the best wood for a pergola?

Pressure-treated timber is popular because it’s durable and designed for outdoor use. Cedar and hardwoods can also work well, but they tend to be the more premium option. 

To help you find which option suits you better, check out our recent blog Pressure Treated Timber or Untreated: Which should you buy?

How deep should pergola posts be set?

This depends on the height of your pergola and the ground conditions it’s built on, but a common approach is around 600mm or more for stability.

Can I build a pergola on paving slabs?

Yes, but you’ll need secure post bases and strong fixings. Make sure the slabs are stable to offer maximum support.

How do I make my pergola more stable?

Use:

• Strong anchors or concrete footings
• Corner braces
• Thicker posts for larger structures
• Quality fixings

How do I maintain a timber pergola?

Check your pergola regularly for:

• Loose fixings
• Signs of rot
• Weathering

Re-treat or stain as needed to keep it protected.

Conclusion

Now you’re ready to build your pergola! If you follow our guide, you’ll be sure to create a stable, strong, and long-lasting pergola that stands out in your garden. 

The most important takeaway from this guide to building a pergola is that planning and accuracy is more integral than the speed you build. 

Once it’s built, you can add your final touches, from lights to an outdoor seating area, and enjoy your new outdoor space. 
To find out more or get tailored advice on your pergola build, get in touch with our team.