Leviathan Wooden Pergola 3m x 3m | 120mm Posts | Smart Seal Treated | Nationwide Installation Included

Leviathan Wooden Pergola – 3m x 3m | 120mm Posts | Smart Seal Timber Treatment

When you want a pergola that truly owns the garden, the Leviathan Wooden Pergola 3m x 3m by Dunster House delivers. With a generous 3m x 3m footprint, imposing 120mm x 120mm upright posts, and a bold open-rafter design, this is a structure that commands the space around it — creating a substantial, defined outdoor room that invites you to live outside.

Imagine a long summer evening: a full dining set beneath the rafters, fairy lights threaded through the beams, the scent of jasmine climbing the posts. The Leviathan 3m x 3m gives you the room to do it properly — to entertain, to relax, to make your garden the place everyone wants to be. With enough internal space for a generous seating arrangement, an outdoor kitchen setup, or even a hot tub, this pergola is as versatile as it is impressive.

Built by Dunster House from slow-grown, pressure treated spruce — not cheap pine — every component is denser, stronger, and engineered to perform through the British seasons year after year. All timber is fully pressure treated (not merely dip treated) and finished with Smart Seal timber sealant as standard, providing a superior barrier against moisture and UV damage. Backed by a 10-year guarantee against rot and insect infestation.

🌟 Professional nationwide installation and Smart Seal timber treatment are both included in the price, free of charge. Our experienced fitting teams cover the whole of Mainland UK — we handle everything from delivery to final fitting so you can simply step outside and enjoy.

Key Features

• ✅ Generous 3m x 3m footprint — ample space for dining, entertaining, or a hot tub
• ✅ Imposing 120mm x 120mm upright posts — premium structural strength and visual impact
• ✅ Slow-grown spruce, not cheap pine — denser grain, superior long-term durability
• ✅ Fully pressure treated (not dip treated) — long-term rot and insect resistance
• ✅ Smart Seal timber treatment included as standard — superior moisture and UV protection
• ✅ 10-year guarantee against rot and insect infestation
• ✅ Pre-notched, pre-cut, planed rafters — precision engineered for a clean, professional finish
• ✅ All fixings included — no hidden extras
• ✅ Perfect for climbing plants — posts and rafters ideal for roses, wisteria, jasmine, and more
• ✅ Nationwide installation included as standard — anywhere across Mainland UK, free of charge

Specifications

• Overall External Dimensions: 3.321m x 3.321m (10' 10.75" x 10' 10.75")
• External Width: 3.040m (9' 11.75")
• External Depth: 3.040m (9' 11.75")
• Internal Width: 2.724m (8' 11.25")
• Internal Depth: 2.724m (8' 11.25")
• Overall Height: 2.350m (7' 8.25")
• Internal Eaves Height: 2.260m (7' 5")
• Upright Posts: 120mm x 120mm
• Timber: Slow Grown Spruce (Fully Pressure Treated)
• Timber Finish: Smart Seal (included as standard)
• Guarantee: 10 Years against Rot and Insect Infestation
• All sizes quoted are nominal. All fixings supplied. Rafters are pre-cut, pre-notched, and planed.

Why Choose Bespoke Oak and Slate?

At Bespoke Oak and Slate, we supply and install premium Dunster House garden structures across the UK. Every Leviathan order includes professional installation and Smart Seal timber treatment as standard — completely free of charge. No hidden costs, no surprises — just a beautifully installed, fully sealed pergola ready for you to enjoy.

Frequently Asked Questions

Does the price include installation?

Yes — professional nationwide installation is included in the price, free of charge. Our experienced fitting teams cover the whole of Mainland UK. The price you see is the price you pay — fully installed, no extras.

What is Smart Seal and is it included?

Smart Seal is a premium timber sealant that provides a superior protective barrier against moisture penetration, UV damage, and weathering — going beyond standard pressure treatment to keep your pergola looking and performing at its best for longer. Smart Seal is applied as standard with every order, free of charge, by our installation team as part of the fitting process.

Do you install anywhere in the UK?

Yes. We install anywhere across Mainland UK at no extra cost. Whether you’re in the South West, the Midlands, Scotland, or anywhere in between — our teams will come to you.

How much space does the 3m x 3m Leviathan provide?

The Leviathan 3m x 3m offers an internal space of 2.724m x 2.724m — comfortably accommodating a 6-seater outdoor dining set, a large corner sofa, or a hot tub with surrounding decking. It’s a genuinely usable outdoor room, not just a decorative feature.

How does the 3m x 3m differ from the 2.5m x 2.5m Leviathan?

The 3m x 3m version offers significantly more internal space — an internal footprint of 2.724m x 2.724m versus 1.83m x 1.83m on the 2.5m model. This makes it the better choice for those who want to use the pergola for dining, entertaining, or housing a hot tub. Both versions share the same 120mm posts, pressure treated spruce, and Smart Seal finish.

What makes the Leviathan different from cheaper pergolas?

The Leviathan is a Dunster House product built from slow-grown spruce, not cheap pine. Slow-grown timber has a denser grain structure, making it significantly stronger and more durable. Combined with full pressure treatment, Smart Seal finishing, 120mm x 120mm posts, and precision pre-notched rafters, the Leviathan is in a different class to budget pergolas.

What is the difference between pressure treated and dip treated timber?

Pressure treatment forces preservative deep into the timber fibres under pressure, providing long-lasting protection from the inside out. Dip treatment only coats the surface and offers far less protection over time. The Leviathan uses full pressure treatment plus Smart Seal as an additional protective layer — which is why it comes with a 10-year guarantee against rot and insect infestation.

Can I grow climbing plants on this pergola?

Yes — the Leviathan’s 120mm x 120mm posts and open rafter design are ideal for climbing plants such as roses, jasmine, clematis, wisteria, and ivy. The larger 3m x 3m frame gives climbing plants even more structure to work with, creating a spectacular natural canopy over time.

Does this pergola need planning permission?

In most cases, a pergola of this size falls within permitted development rights and does not require planning permission, provided it meets standard conditions (e.g. not covering more than 50% of garden area, not positioned forward of the principal elevation). We always recommend checking with your local planning authority if you are unsure.

What are the exact dimensions?

The overall external footprint is 3.321m x 3.321m (10' 10.75" x 10' 10.75"), with an internal space of 2.724m x 2.724m. The overall height is 2.350m (7' 8.25") with an internal eaves height of 2.260m (7' 5"). All sizes are nominal.

Are all fixings included?

Yes — all fixings needed for assembly are included at no extra cost. As installation is included as standard, our professional team handles the entire build for you.

What is the guarantee?

The Leviathan Wooden Pergola 3m x 3m comes with a 10-year guarantee against rot and insect infestation on the pressure treated timber, provided the care instructions supplied by Dunster House are followed.