Replace your decking.

Whether you are upgrading from traditional softwood to modern composite or simply refreshing a tired seating area, a professional replacement ensures the subframe is structurally sound and the finish is built to last. This guide outlines the essential steps, current UK market costs, and regulatory requirements for a successful decking project.

What Does the Work Involve?

• Site Survey: A thorough inspection of the existing boards and, more importantly, the subframe to check for rot, fungal growth, or structural subsidence.
• Demolition and Disposal: Careful removal of old boards, railings, and joists, followed by responsible disposal—often involving a skip or a waste carrier license for treated timber.
• Subframe Preparation: Levelling the ground, installing new support pads or posts, and laying a heavy-duty weed membrane with gravel to prevent growth beneath the deck.
• Structural Framing: Constructing or repairing the joist network, ensuring correct spacing (especially critical for composite boards) and applying joist protection tape.
• Board Installation: Fitting the new surface using hidden fasteners or specialist decking screws, ensuring uniform expansion gaps for drainage and movement.
• Finishing Touches: Installing fascias, picture-framing edges, fitting balustrades, and applying end-grain preservatives to any cut timber.

Typical Costs

Costs are heavily influenced by your choice of material and the condition of the ground beneath. While softwood is budget-friendly, composite decking often proves more cost-effective over its 25-year lifespan due to zero staining and oiling requirements.

How Long Does It Take?

• Small Deck (up to 15m²): 2–3 days for removal and full replacement.
• Medium Deck (20–40m²): 4–6 days, depending on the complexity of the layout.
• Large or Multi-level Decks: 1–2 weeks, especially if significant structural groundworks are required.
• Additional Features: Allow an extra 1–2 days for integrated lighting, complex stairs, or glass balustrades.

DIY or Professional?

Replacing a few surface boards is a manageable DIY task for a confident homeowner. However, a full replacement involving the subframe is a structural project that usually requires a professional landscaper or carpenter.

Proper joist spacing and airflow ventilation are critical; if these are done incorrectly, even the most expensive composite boards will sag or trap moisture, leading to premature failure.

If your deck is more than 600mm off the ground, it is considered a "raised platform" and must meet specific safety standards regarding weight loads and railings. Professionals will also ensure compliance with Part M of the Building Regulations if the deck affects the primary access to your home.

Choosing the Right Tradesperson

• Verify Experience: Ask to see a portfolio of completed decks, specifically looking for projects that have aged 2-3 years to see how they have held up.
• Check Qualifications: Look for members of the Association of Professional Landscapers (APL) or the British Association of Landscape Industries (BALI).
• Waste Management: Ensure they hold a valid Environment Agency waste carrier license to legally dispose of your old treated timber.

• What joist centres will you use for this specific board type? (Composite usually requires 300mm or 400mm centres).
• Will you be using joist tape to protect the subframe from water ingress?
• Is the quote inclusive of skip hire and all VAT?
• What is the manufacturer's warranty on the boards, and what is your personal guarantee on the labour?

UK Regulations

• Planning Permission: Generally not required unless the deck is more than 300mm above the ground or covers more than 50% of your garden area.
• Building Regulations: Apply to any deck that is part of a fire escape route or is significantly elevated (typically over 600mm).
• Conservation Areas: If you live in a protected area or a listed building, you must consult your local planning office before changing materials (e.g., switching timber for composite).

Common Problems

• Inadequate Drainage: If the ground beneath isn't sloped or prepared, water will pool, causing the subframe to rot from the bottom up.
• Incorrect Expansion Gaps: Boards fitted too tightly will buckle in summer; those fitted too loosely become a trip hazard and look unsightly.
• Poor Subframe Ventilation: Lack of airflow is the primary cause of "dry rot" in UK decks; professional installers will ensure a minimum 25mm clearance.
• Using the Wrong Fixings: Standard screws will corrode and snap; only high-grade stainless steel or coated deck screws should be used to prevent "blackening" of the wood.

Frequently Asked Questions