Designing and Building Garden Decking

Decking is a popular choice for UK gardens due to its versatility and ease of construction. Unlike raised patios, a raised deck requires less groundwork and blends seamlessly with natural elements like trees and fences.

However, decking is still a form of carpentry, so basic DIY skills are needed for a professional finish.

This guide focuses on designing and building a simple raised deck. Whether your deck is slightly elevated or raised, we will go through all you need to know to arrive at a successful finish.

Understanding the Different Types of Decking

If you’re planning a deck in your UK garden, one of the first things you’ll need to decide is the type of decking material. There are several options top go for in the UK, here are the most common.

Pressure‑Treated (Softwood) Decking

This is the classic and most budget‑friendly choice. Made from UK‑grown softwoods like pine or fir, it’s pressure‑treated to resist rot and insects. You’ll spot green‑tinged boards from the treatment process. It’s straightforward to work with and easy to fix or replace if needed.

While it doesn’t have the rich colour of hardwoods, you can apply a suitable UK exterior wood stain or sealant every year or two to keep it looking fresh. A great starter‑option for straightforward, low‑cost garden decks.

Hardwood Decking

Hardwoods, such as oak, Iroko or Accoya (a sustainably sourced option popular in the UK), are naturally strong, durable, and often rich in warm tones. They’re perfect if you want your decking to last decades with minimal maintenance, as hardwood doesn’t warp or fade as easily.

In the UK climate, hardwood decking benefits from an occasional wash and re‑oil nice and easy to maintain if you’d prefer a more natural look that ages gracefully.

Composite Decking (Wood‑Plastic Composites)

If you’re after low maintenance and consistent colour, composite decking is a solid pick. Made by blending recycled plastics with wood fibres, these boards resist rotting, splintering, and fading—ideal for wet UK summers and damp winters.

They come in a wide range of colours and textures, from smooth modern styles to wood‑grain finishes.

Though initially pricier, the long‑term savings on maintenance and sealants make it a popular choice for busy homeowners.

PVC / Plastic‑Only Decking

Pure PVC decking (100 % plastic) is fully water‑resistant and ideal if you have an area exposed to lots of moisture, such as near ponds, on rooftops or over balconies. There’s zero risk of mould or rot, and it’s very easy to wash clean.

However, PVC can feel more synthetic underfoot, and colour options are usually more limited than composite or wood varieties.

Despite this, for special UK locations, such as balcony decks with heavy rain exposure, it’s a smart, low‑effort solution.

Recycled Timber Decking

Made from reclaimed or recycled wood, often from old buildings or railway sleepers, this type of decking is eco‑friendly and full of character.

Each board is unique, with natural nail holes, grain patterns, and rustic patina, perfect if you’re after a rustic or vintage style in your UK garden.

Expect to treat or seal it well before installation to preserve both the look and durability, but it’s a charming, sustainable pick for those who love something with history.

Can You Build Decking Over a Patio?

Yes, you can build decking over a patio as long as the surface is solid and level. The frame should follow the natural slope of the patio so rainwater drains away and does not pool against the timber.

Plan your decking layout before you start. Mark post positions, check they land on firm ground, and size your timbers correctly. Stronger timbers allow posts to be spaced further apart, creating a stable and long-lasting deck.

Always make sure the patio beneath is strong enough to carry the weight of the new deck and any furniture or foot traffic it will support.

What Timbers Should Be Used to Build a Deck?

Picking the right timber is key to building a strong, long-lasting deck that can handle the UK’s weather. The best options are durable, rot-resistant, and low maintenance. Below are the most common choices.

Softwood Decking (Affordable and Popular)

Softwood, usually pine or spruce, is the UK’s most widely used decking timber. It’s budget-friendly, easy to work with, and pressure-treated to resist rot, insects and fungi.

Hardwood Decking (Durable and Weather-Resistant)

Hardwoods like oak, teak, and iroko are naturally dense and long-lasting. They offer excellent resistance to moisture and decay, making them ideal for premium decks.

Composite Decking (Low Maintenance and Eco-Friendly)

Composite boards, made from recycled plastics and wood fibres, are highly durable. They resist moisture, mould, and fading while needing very little upkeep.

When building your deck frame, use 225 x 50mm timbers. Space support posts no more than 2m apart, or up to 4m between frame ends if joists are 450mm apart. A 4m x 4m deck can be built with just eight posts, but for maximum strength we recommend 100mm square posts.

Decking boards are supplied with grooves to improve grip and drainage. Always lay them with a slight fall so rainwater runs off easily.

Where Should I Place the Posts?

Correct post placement is vital for building a safe, stable deck. Posts provide the main support, so they must be positioned in the right spots before you start fixing the frame.

The simplest method is to build your deck frame first, then lay it on the ground. Mark the post positions directly beneath the frame, remove it and install your posts in the marked locations.

The diagram below shows how the frame sits under the decking boards, with post locations clearly marked.

Once positions are confirmed, set the posts securely in the ground using the same method as concreting fence posts. For step-by-step instructions, see our post concreting guide.

Where Should I Put My Decking?

Choosing the right spot for your decking makes it more practical, comfortable and longer lasting.

A deck built in constant shade will often stay damp, encouraging algae, lichen and eventually timber rot. Even treated softwood can decay if it doesn’t dry out properly.

For a warmer, low-maintenance deck, place it where it receives good sunlight. This might not always be right next to the house, so think about when and how you’ll use the space before deciding on the best location.

Do You Need Planning Permission for a Decking Area?

One of the first questions in any garden decking project is whether planning permission is required or not. In most UK homes, decking can be built without formal approval, but there are important exceptions.

When Planning Permission is Not Needed

In general, you don’t need permission if your decking follows these rules:

• Height: Decking is no more than 300mm (about one foot) above ground level.
• Garden Size: It covers no more than 50% of the total outdoor space, including other outbuildings or patios.
• Boundaries: It does not extend too close to neighbouring properties and stays within the height and size limits above.

When Planning Permission is Required

You may need to apply for planning approval if any of the following apply:

• Raised Decking: Anything higher than 300mm usually requires permission.
• Listed Buildings or Conservation Areas: Extra rules apply, so permission is normally needed even for low decking.
• Property Restrictions: Some homes have specific planning conditions that cover all external changes, including decking.

Can Decking Timbers Overhang Posts?

Yes — decking boards can safely overhang the frame, but only within sensible limits. A good rule of thumb is to test the overhang by standing on it to check it feels solid and stable.

Allowing timbers to overhang makes it easier to create curves, rounded edges or custom shapes that blend naturally into your garden. Always plan your deck’s outline first, then adjust the frame to support the design.

For example, in one Somerset project we curved a deck edge so it projected about 400mm over a pond, giving the deck a smooth flow while still remaining strong and secure.

How to Build a Basic Deck

Decking is one of the simplest ways to add a stylish outdoor space for relaxing, dining or entertaining. With the right preparation, you can transform even a plain garden into a usable living area.

Below, we outline the key steps to building a straightforward decking area, using plain instructions that anyone can follow, even if you’re new to DIY.

Step 1: Plan Your Decking Area

The first step is to choose the right spot and set out your deck clearly. Good planning will save time and prevent costly mistakes later. Choose the location carefully, thinking about how much sun or shade you want.

• Mark the space: Use string and pegs to outline the area where your decking will sit.
• Check measurements: Make sure the size works with your garden’s layout and leaves room for access.
• Decide the type: Ground-level decks sit on gravel or concrete pads, while raised decks need support posts.

Step 2: Prepare the Ground and Lay a Base

A solid base is the key to safe, long-lasting decking. It must clear, level and support the ground properly before building.

• Ground-level decks: Remove grass and debris, then lay a weed membrane topped with gravel or concrete pads for drainage and stability.
• Raised decks: Dig post holes at least 300mm deep and fix the posts securely with quick-setting concrete (postcrete).
• Drainage matters: Always allow water to run off freely to prevent movement or rot over time.

Step 3: Construct the Deck Frame

The frame forms the backbone of your decking, so build it strong and level from the start.

• Use treated timber: Create a square or rectangular frame with pressure-treated joists to resist rot.
• Secure fixings: Join the frame with galvanised or decking screws designed to prevent rust.
• Check levels: Use a spirit level to ensure the frame is perfectly even before fixing it in place.

Step 4: Install the Decking Boards

With the frame in place, you can now fix the boards securely for a strong, long-lasting deck.

• Lay boards across joists: Position boards at right angles to the joists for maximum strength.
• Allow for movement: Leave a 5mm gap between boards to aid drainage and prevent warping.
• Fix with care: Drill pilot holes and use decking screws to avoid splitting the timber.
• Finish neatly: Stagger board joints where possible and trim any overhang for a clean, professional look.

Step 5: Finishing Touches and Maintenance

Proper finishing and regular care will keep your decking safe, durable, and looking its best:

• Protect the surface: Apply decking oil, stain or paint to shield the timber from rain, sun and frost.
• Keep it clean: Sweep often and wash with decking cleaner to stop algae, mould and dirt buildup.
• Re-treat annually: Refresh the finish each year to prevent warping, splitting and premature wear.

Safety note: Decks raised more than 300mm usually require a handrail. Fix posts securely to the frame or set them in concrete. Always check for drains or underground services before digging.

Basic Decking Maintenance – How to Care for Your Deck

Looking after your decking properly will keep it safe, strong and looking great all year round. Without regular care, timber decks can quickly suffer from rot, mould or loose fixings that make them unsafe. Follow these simple steps to protect your deck and extend its life.

• Inspect regularly: Check for splinters, loose nails, mould or soft spots. Treat problems early before they spread or stain the wood permanently.
• Clean and protect: Use a specialist decking cleaner or wood preserver that tackles slime, algae and bacteria. Make sure it soaks deep into the timber for lasting protection.
• Seasonal treatment: Apply a quality preservative in spring and autumn to defend against rot, fungi and insect attack.
• Watch the end grain: The cut ends of boards and any timber touching the ground are most at risk of decay. Seal them with decking oil or exterior wood treatment.
• Keep the natural look: For a fresh, natural finish, apply decking oil regularly to nourish and protect the wood.

Safety tip: Keep children and pets away while treatments dry, and avoid letting chemicals run onto plants or garden ponds.

Decking Preservative

To keep your decking strong and weather-resistant, regular cleaning and treatment are essential. Use a specialist decking cleaner, then apply a preservative or decking oil once a year to protect against water damage and fading.

Decking stains and oils come in clear or coloured finishes, so you can choose the look that suits your garden. When treating, avoid letting preservatives run onto plants, soil or ponds.

Pay special attention to cut ends and exposed posts, as these are most vulnerable to rot. Seal them with a quality wood preservative for extra protection.

Important: Never burn treated timber. Always take it to a licensed waste disposal site, as burning can release harmful chemicals.

Final Points to Consider

Before finishing your decking project, remember these key points: plan your layout carefully, use quality materials and commit to ongoing maintenance. A little care goes a long way to ensure your deck remains safe, attractive and long-lasting.

Garden Furniture

Wooden garden furniture needs protection from the weather to stay in good condition. In bad weather, cover it or store it indoors and always keep cushions dry to prevent mould. Treat natural wood twice a year with protective oil in spring and autumn.

If you prefer low-maintenance options, consider furniture made from metal, resin or plastic. These modern materials resist rot, fading and insect damage while offering long-lasting durability for any style or budget.

Decking Problems and Solutions

Decking naturally weathers over time, which can cause stains, mould or even rot. The way it reacts depends on the timber type, treatment and how it’s built. Below are common issues and how to prevent them:

Softwood Decking

Softwood (like pine) is affordable but less durable. It can turn grey unless treated regularly with decking oil. Choose pre-treated boards or apply treatment yourself to extend its life.

Hardwood Decking

Hardwoods such as oak, teak or iroko last longer and resist rot and insects, but they are heavier and more expensive. Regular oiling is still needed to keep their colour and protect against greying.

Mould and Fungi

Unchecked mould can stain and weaken timber. Apply a preservative twice a year, ideally in spring and autumn, to stop growth before it spreads.

Damp and Rot

Timber in contact with soil or standing water is vulnerable to rot. Protect these areas with quality decking oils or specialist treatments such as Cuprinol 5 Star or Everbuild Lumberjack.

Smooth vs Ridged Boards

Smooth boards give a modern look, while ridged boards improve grip when wet but may feel rough under bare feet. Choose the finish that suits your style and use.

Deck Fixings

Screws are better than nails for fixing decking. They create a neat finish, are easier to remove and won’t work loose when the timber expands and contracts.

Sustainability

Choose decking from sustainable sources. Look for FSC-certified timber and ask your supplier where the wood is sourced to ensure it’s environmentally responsible.

Building a decking area can transform your outdoor space and bring a whole new dimension to your garden, but for it to last, it must be built correctly and maintained year-round.