Bridges and Boardwalks for Suitable Alternative Natural Greenspaces

Suitable Alternative Natural Greenspaces, usually shortened to SANGs, are designed to give people an attractive place to walk, exercise and enjoy nature while reducing recreational pressure on protected habitats.

They are often created or improved alongside new housing developments, particularly where increased visitor numbers could affect a Special Protection Area or another environmentally sensitive site. For a SANG to work, however, it must be somewhere people genuinely choose to visit. A designation on a planning document will not persuade anyone to change their favourite walking route.

Good paths, welcoming entrances and reliable access across wet or difficult ground all help turn a piece of land into a usable and appealing natural greenspace.

What is a SANG?

SANG stands for Suitable Alternative Natural Greenspace. You may also see the plural written as either SANG or SANGs.

Its purpose is to provide an attractive recreational alternative to a protected natural site. By giving residents somewhere else to walk, exercise dogs and spend time outdoors, a SANG can help reduce additional visitor pressure associated with nearby residential development.

Natural England explains that the effectiveness of a SANG depends heavily on its location and design. It needs to offer the type of experience that attracts the same people who might otherwise visit the protected site.

SANGs are particularly well established around the Thames Basin Heaths. More than 80 have been created or improved in this area, providing almost 2,000 hectares of additional or enhanced greenspace and helping to protect sensitive heathland habitats.

Making a SANG attractive and easy to explore

People are more likely to return to a greenspace when the route feels natural, interesting and straightforward to follow.

Depending on the landscape, a SANG may include:

• Circular walking routes
• Woodland and open grassland
• Wetlands, ponds and streams
• Dog-walking areas
• Accessible paths
• Bridges across watercourses and drainage channels
• Boardwalks over wet, boggy or environmentally sensitive ground
• Gates, waymarkers and entrance features

These elements should work together. A carefully planned walking route loses much of its appeal if sections regularly become waterlogged, bridges feel unstable or timber boardwalks are repeatedly closed for repairs.

Boardwalks for wet and sensitive SANG sites

Boardwalks can make valuable areas of a SANG accessible without requiring extensive excavation, drainage or hard surfacing.

They are particularly useful for routes passing through:

• Wet woodland
• Marshy ground
• Flood-prone areas
• Pond margins
• Ecologically sensitive habitats
• Areas with poor or unstable ground conditions

A raised boardwalk can guide visitors along a defined route while helping to reduce trampling and the gradual widening of muddy paths. It can also open parts of a site that would otherwise become difficult or unpleasant to use during wetter months.

Built by Bison manufactures and supplies Re-Life recycled plastic boardwalk systems for parks, nature reserves, country parks and Suitable Alternative Natural Greenspaces throughout the UK.

The structural posts, joists and deck boards are manufactured from recycled plastic, creating a system that does not rot, warp or require preservative treatment. This makes it particularly well suited to damp locations where conventional timber components may have a limited working life.

Long-life bridges for SANG walking routes

Streams, drainage ditches and changes in ground level can add character to a SANG, but they can also divide a walking route.

A well-positioned pedestrian bridge allows the path to continue naturally through the landscape. It can help create a more interesting circular walk, provide access to previously disconnected areas and reduce the temptation for visitors to form unofficial routes across vulnerable ground.

Built by Bison manufactures and supplies pedestrian bridge kits for SANG projects, including:

• Bridges for walkers and dog walkers
• Wider bridges for shared pedestrian and cycle routes
• Bridges with recycled plastic or timber decking
• Structures with timber, steel or recycled plastic parapets
• Short crossings supplied from stock
• Bespoke bridges for longer or more complex spans

Our standard stock bridge range includes 1.2-metre-wide pedestrian bridges in spans from 3 to 10 metres, available with Re-Life 100% recycled plastic or SureGrip-Duo timber decking. Each kit includes the required components and assembly instructions, helping projects move forward without the lengthy lead times normally associated with a bespoke structure.

Longer and wider bridges can also be designed and manufactured to suit the route, expected users and site conditions.

Planning for the whole life of the SANG

SANG infrastructure should not be judged only by how it looks when the site first opens.

These greenspaces are expected to remain available and attractive over the long term. Natural England guidance states that SANGs associated with housing should be delivered before occupation and funded for ongoing management in perpetuity.

That makes maintenance an important design consideration from the outset.

In wet or shaded environments, timber elements can deteriorate more quickly than expected. Repeated repairs create additional costs and may require paths or sections of a route to be closed. A boardwalk or bridge that is unavailable for several months does little to help a SANG compete with an established protected landscape nearby.

Using recycled plastic, galvanised steel and carefully selected decking materials can reduce future maintenance requirements and provide greater confidence in the long-term availability of the route.

Infrastructure that fits the landscape

Durability matters, but SANG bridges and boardwalks should not feel like urban structures dropped into the countryside.

Material, colour, parapet style and route alignment can all be adapted to suit the setting. Recycled plastic can provide a low-maintenance solution with a natural appearance, while timber decking or parapets may be selected where a more traditional finish is preferred.

The aim is to create access infrastructure that performs reliably without becoming the main event. The landscape should keep that job.

SANG bridges and boardwalks from Built by Bison

Built by Bison works with local authorities, developers, landscape architects, contractors and countryside teams to manufacture and supply bridges and boardwalk systems for SANGs and other public greenspaces.

We can help with individual crossings, replacement structures or bridge and boardwalk packages forming part of a wider access route.

Early project information such as the required span, path width, ground conditions, expected users and preferred materials allows our team to recommend a practical system for the site.

For help specifying a pedestrian bridge or long-life boardwalk for a Suitable Alternative Natural Greenspace, contact Built by Bison.