Last updated: January 2025

Raised Deck with Railing — Full Materials List

A raised deck — typically 600mm or more above ground level — requires railing for safety and may need building regulations approval. This example covers a 4m × 3m raised hardwood deck with railing on three sides, showing the complete materials list including railing components that ground-level decks do not need.

Project Profile

• Deck size: 4m × 3m (12 m²), raised 750mm
• Material: Hardwood (145mm wide)
• Layout: Standard parallel
• Railing: 3 sides (house-side open), 900mm high
• Joist spacing: 450mm

Deck Surface & Subframe

Boards: 20 across × 2 per row = 40, +10% = 44 hardwood boards at 2.4m lengths. Joists: 10 at 3m each. Bearers: 3 at 4m. Posts: 12 structural posts at 750mm height (plus depth into foundations).

Raised decks need more robust posts than ground-level builds. Each post should be bolted to a concrete pad foundation with galvanised post brackets. The posts carry the full weight of the deck plus occupants, so 100×100mm treated timber is typical (larger than the 75×75mm often used at ground level).

Railing Calculation

Railing runs along 3 sides: 4m + 3m + 4m = 11 linear metres (excluding the house-side). Railing posts at 1,200mm spacing: (11,000 ÷ 1,200) + 1 = 11 railing posts. Each section between posts needs 2 horizontal rails (top and mid-rail) at the gap width. Total rail length: approximately 11m × 2 = 22 linear metres of rail.

UK building regulations require railing at least 900mm high on any deck more than 600mm above ground. Baluster spacing must not allow a 100mm sphere to pass through (for child safety). Spindles or vertical balusters between the top and bottom rail at approximately 100mm centres will meet this requirement — budget for approximately 100 spindles for 11 metres of railing.

Railing Material Options and Cost Considerations

Railing materials significantly impact both the aesthetics and budget of a raised deck. Common options include pressure-treated timber, composite, aluminium, and glass infill.

• Timber railing: The most cost-effective and matches traditional hardwood decking, but requires regular staining or painting every 2–3 years to prevent rot and fading.
• Composite railing: Offers low maintenance and long-term durability, often coming with a 10–25 year warranty, though it typically costs 20–40% more upfront than timber.
• Aluminium railing: Provides a modern, sleek look and is highly resistant to corrosion and weathering—ideal for coastal or high-moisture areas—but tends to be the most expensive option.
• Glass balustrades: Offer unobstructed views but require careful installation to meet safety standards and may involve additional structural supports.

For a 4m × 3m raised deck, budgeting £800–£2,200 for railing (including posts, rails, and spindles) is typical, depending on material choice. Always verify local building regulations, especially regarding load requirements and fire performance for public or commercial installations.

Foundation and Structural Support Details

A 750mm-high raised deck demands robust foundation design to ensure stability and longevity. Each 100×100mm post should sit in a concrete pad foundation at least 600mm deep, with the top of the pad level and set below frost line (typically 450mm in most UK regions). Post brackets must be galvanised (minimum BZ or HDG) and secured with M12 anchor bolts.

For added rigidity, especially on larger decks, consider installing a rim joist around the perimeter and using hanger brackets to connect bearers to posts. Soil type matters too: clay soils may require deeper footings or pile foundations to prevent settlement. A structural engineer’s sign-off is recommended if the deck abuts the house—especially where fixing to the building structure—since improper attachment can compromise the home’s damp-proof course or structural integrity.

Remember, building regulations approval is usually required for decks over 300mm high and within 1m of a boundary, or over 600mm high regardless of location. Engaging a Part P or HDB-approved builder can simplify compliance and reduce risk of costly rework.

Safety, Accessibility, and Maintenance Tips

Beyond meeting regulatory standards, safety and usability should guide every decision in raised deck design.

• Non-slip finishes: Grooved or textured surfaces are essential, especially in wet climates—common across the UK.
• Edge lighting: Consider adding low-voltage LED strips along railings for evening use; they are safe and easy to install.
• Accessibility: Ensure access points are wide enough (minimum 900mm clear width) and avoid abrupt height changes. For elderly or mobility-impaired users, a gentle ramp with handrails may be more appropriate than steps.

Maintenance is vital: inspect posts and brackets annually for corrosion or rot, especially where timber meets concrete; reseal joints and fasteners every 2–3 years; and clean debris from beneath the deck to prevent moisture buildup and pest infestation. A well-maintained raised deck can last 15–25 years, but neglecting post-footing drainage or ignoring early signs of structural movement can lead to costly repairs—or worse, failure. Proactive care not only extends longevity but also safeguards users.

Choosing the Right Decking Material

When building a raised deck with railing, selecting the appropriate decking material is crucial for both aesthetics and longevity. Hardwood, such as cedar or larch, offers natural beauty and durability but requires regular maintenance like staining or sealing. Composite decking, on the other hand, provides low maintenance benefits with a lifespan that often exceeds that of timber. It's also resistant to weathering, rot, and insect damage. For a raised deck, consider materials that can withstand varying weather conditions and foot traffic. In the UK, pressure-treated softwoods are also a cost-effective option for those seeking a traditional look without the high maintenance of natural hardwoods.

Safety Considerations and Building Regulations

In the UK, raised decks over 600mm above ground level often require compliance with building regulations to ensure safety. These regulations typically mandate railings that are at least 900mm high, as specified in Approved Document M. Additionally, the spacing between balusters must not exceed 100mm to prevent children from slipping through. When planning your project, consider consulting with a local authority or a structural engineer, especially for decks that will support significant weight or are located near public areas. Proper foundation work is also essential, particularly for raised structures, to ensure stability and longevity.

Installation Tips for Raised Decks with Railing

Installing a raised deck with railing requires careful planning and attention to detail. Start by ensuring your ground-level foundations are solid, typically involving concrete footings that extend below frost line in the UK climate. Use treated timber posts and ensure they're properly secured with galvanised brackets. For the railing, pre-drill holes to avoid splitting the wood and use appropriate screws or bolts for a secure fit. Consider adding a small overhang to your deck boards to protect the railing from weather exposure. Finally, always allow for expansion and contraction of materials, particularly in composite decking, by using appropriate fixings that accommodate movement without compromising structural integrity.

Cost Breakdown

Key Takeaways

• Railing adds approximately £480–600 to materials — a significant portion of a raised deck budget.
• Raised decks require building regulations approval in most UK local authorities.
• Cross-bracing between posts is essential for lateral stability at this height.
• Consider using our calculator with railing enabled to get exact quantities for your dimensions.

FAQ