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Drives, Paths and Garden Landscaping – NHBC Standards 2023 (Chapter 10.2)

New Build Garden Regulations

The NHBC (National House Building Council) is a warranty and insurance provider for new homes in the UK. They set technical standards and requirements for various aspects of home construction, including drives, paths, and landscaping. Their technical requirements for drives, paths, and landscaping are designed to ensure that these areas are constructed to a high standard, promoting durability, safety, and functionality.

The NHBC requires compliance with their technical standards and requirements for drives, paths, and landscaping. Builders and developers are expected to adhere to these guidelines during the construction process. It emphasizes the importance of providing clear and comprehensive designs and specifications for drives, paths, and landscaping. This includes detailing the layout, dimensions, gradients, and material specifications.

Stability is a crucial aspect when constructing drives, paths, and landscaping. The NHBC specifies that flexible retaining walls should not be used as the primary support for homes or roads. Adequate design and construction of freestanding walls and retaining structures, considering factors such as masonry, concrete, and geotechnical design, are required to ensure stability.

Guidelines for safety measures in drives, paths, and landscaping are provided. This includes requirements for guarding on retaining structures and steps to prevent falls or accidents.

General construction considerations for drives, paths, and landscaping are outlined below. This includes proper drainage to avoid water accumulation, stability precautions to prevent subsidence or movement, and the use of suitable materials that meet the necessary technical standards.

Minimum thickness requirements are specified for different elements such as sub-base, house paths, and patios. These specifications ensure that the constructed surfaces are robust and durable.

The NHBC’s technical requirements provide guidance on the use of suitable materials for drives, paths, and landscaping. This includes considering factors such as load-bearing capacity, weather resistance, and durability.

By following the NHBC’s technical requirements for drives, paths, and landscaping, builders and developers can ensure that these areas are constructed to a high standard, promoting longevity, safety, and overall satisfaction for homeowners.

 


 

Slopes and Gradients in New Build Gardens

When it comes to the slopes and gradients in your new build home’s garden, there are a few important factors to consider. While there is no specific requirement for a level garden under NHBC standards, it’s essential to understand how the topography of the site influences the garden’s design.

Working with the Topography

In most cases, if your new build site is on a slope, it’s expected that your garden will reflect this natural contour. The NHBC emphasizes that the garden should follow the topography of the site, allowing for a harmonious integration with the surrounding landscape. This means embracing the unique characteristics of the terrain rather than attempting to level off the entire area.

Developer Promises and Negotiations

There may be exceptions to the general rule of following the site’s topography, particularly if you have negotiated specific terms with the developer regarding a level garden. If you have written documentation or have been promised a level garden during negotiations, these agreements should be honored. However, it’s crucial to clarify such arrangements beforehand to avoid any misunderstandings.

Dealing with Steep Slopes

When faced with steep slopes in your garden, it’s essential to consider suitable treatments. The NHBC provides guidelines regarding the steepness of slopes and how areas should be addressed. These guidelines aim to ensure safety, functionality, and proper drainage. Depending on the gradient, you may need to incorporate steps, terracing, or other appropriate measures to create a usable and visually appealing space.

While NHBC standards do not mandate a level garden for new builds, understanding the role of slopes and gradients is essential for designing a garden that complements your home and the surrounding environment. By embracing the natural topography and considering suitable treatments for steep areas, you can create a beautiful and functional garden that meets your expectations. Remember to review any developer promises or negotiated agreements to ensure they align with your desired outcome.

 


 

Waterlogging and Drainage Issues in New Build Gardens

NHBC guidelines emphasize the importance of preventing waterlogging in areas within 3 meters of the habitable parts of the home. These guidelines are designed to ensure that homeowners have adequate access and utility around their property without facing the issue of waterlogged gardens.

Here are some key considerations based on the NHBC guidelines:

Soil Selection and Management

Proper soil selection and management play a crucial role in preventing waterlogging. The NHBC recommends using well-draining soils that can efficiently absorb and disperse excess water. Soils with a high clay content tend to retain water and can contribute to waterlogging issues. By selecting soils with better drainage properties, the risk of water accumulation near the habitable parts of their home can be reduced.

Drainage Systems

When appropriate soil selection alone is not sufficient, implementing drainage systems becomes necessary to prevent waterlogging. The NHBC encourages the use of suitable drainage solutions in areas where waterlogging is likely to occur. This may include the installation of subsurface drainage systems, such as French drains, perforated pipes, or gravel-filled trenches. These systems collect and redirect excess water away from the garden, preventing it from accumulating near the home.

Suitable Means

Apart from drainage systems, the NHBC guidelines also highlight the use of “other suitable means” to prevent waterlogging. This encompasses various techniques that can be employed based on the specific circumstances of the garden. For example, the use of raised beds or containers can elevate plants above waterlogged soil, allowing excess water to drain more effectively. Implementing appropriate landscaping techniques, such as grading and sloping, can also aid in preventing water accumulation near the home.

Professional Guidance

To ensure compliance with NHBC guidelines and to address waterlogging effectively, it is advisable to seek professional guidance. Consulting with landscape architects, garden designers, or drainage specialists can provide valuable insights and recommendations tailored to your specific garden and home. These professionals can assess the site, identify potential issues, and suggest appropriate measures to prevent or mitigate waterlogging problems.

 


 

Drives, Paths and Garden Landscaping – NHBC Standards 2023 (Chapter 10.2)

This chapter provides guidance on meeting the Technical Requirements for drives, paths and landscaping, including:

  • private roads
  • shared private drives
  • private drives
  • car parking areas

Definitions for this chapter

Commercial vehicles

Commercial vehicles are typically vehicles weighing in excess of 3.5 tonnes or capable of moving a payload of more than 1 tonne. Examples are delivery trucks, buses, large vans, bin lorries, and fire trucks.

Flexible retaining walls

Are typically walls that support the soil laterally and allow larger deformations of the unsupported edge of the wall compared to stiff or rigid retaining walls. Typical examples of these include any or a combination of the following: vegetated such as geotextile bagged walls, earth-reinforced and most gravity retaining wall structures such as gabion, crib, block or modular retaining wall systems.

Garden

Is the land within the curtilage up to 20m from the habitable parts of the home (i.e. not garages/ outbuildings). This distance is measured from the external walls.

Home

Includes a house, bungalow, flat or maisonette.

Light vehicles

Light vehicles are typically vehicles weighing up to 3.5 tonnes, and these include cars, SUV’s, vans and minibuses.

Private drives

Are usually located adjacent to a property and typically within the curtilage of that property. Private drives and parking areas where located away from the immediate vicinity of a properties would usually have a barrier to ensure it is only used by cars and or light vehicles.

Private roads

Are roads that are unadopted or not maintained at public expense. They are usually wide enough for single traffic in opposite directions simultaneously, and may or may not have adjoining footpaths. Private roads will be expected to support frequent use by commercial vehicles.

Shared drives

Are usually single track private ‘roads’ to access private drives or private properties. Shared drives would be expected to support the occasional commercial vehicles on them.

Shared parking

Are typically communal parking area, which is accessible to the general public but are not adopted. There is usually little or no restriction regarding what type vehicles they are accessible to. They can sometimes act a turning head at the end of a public/ adopted road. Shared parking and access road/ areas to them are expected to support frequent use by commercial vehicles.

10.2.1 Compliance

Drives, paths and landscaping shall comply with the Technical Requirements.

Drives, paths and landscaping that comply with the guidance in this chapter will generally be acceptable.

All works should be completed in accordance with:

  • the design, and
  • the ground remediation statement (where applicable).

Formation levels should be set out in accordance with the design.

10.2.2 Provision of information

Designs and specifications shall be produced in a clearly understandable format, include all relevant information and be distributed to the appropriate personnel.

All works relating to drives, paths and landscaping should be fully specified.

Designs and specifications should be issued to site supervisors, relevant specialist subcontractors and suppliers.

10.2.3 Stability

Precautions shall be taken to ensure stability of the ground.

Where the ground may become surcharged during construction, precautions should be taken to ensure stability.

Flexible retaining walls such as gabion and timber structures should not be used to provide support to homes, garages, roads, drives, car parking areas or drainage systems.

Retaining structures that give support to the foundations of a home should be completed before work starts on the construction of the foundations of the home.

10.2.4 Freestanding walls and retaining structures

Freestanding walls and retaining structures shall be adequate for their intended purpose.

Freestanding walls should be in accordance with:

  • BS EN 1996-1 ‘Design of masonry structures’
  • PD 6697 Recommendations for the design of masonry structures.

Retaining structures should be in accordance with:

  • BS EN 1992 ‘Design of concrete structures’.
  • BS EN 1996 ‘Design of masonry structures’.
  • BS EN 1997-2 ‘Geotechnical design. Ground investigation and testing’.
  • BRE Good Building Guide 27 ‘Building brickwork and blockwork retaining walls’.

All retaining structures, more than 600mm high, should be designed by an engineer in accordance with Technical Requirement R5.

Where timber structures more than 600mm high are used for retaining ground in boundary situations, they should be designed with a desired service life of 60 years.

Where planters are provided, they should be designed to support the volume of retained soil and the plant species.

10.2.5 Guarding and steps

Retaining structures and steps shall be adequately guarded and allow safe use.

Guarding should be provided where:

  • structures are retaining land more than 600mm high to which people have access
  • a retaining structure is more than 600mm high and the dimension from the top of the retaining wall to the higher ground level is less than 300mm, or
  • a path is adjacent to a vertical difference in level of more than 600mm (including where ground adjacent to the path falls away at an angle of more than 30° from the horizontal).

The guarding should:

  • be a minimum of 1100mm high
  • not be readily climbable by children
  • not allow a 100mm diameter sphere to pass through.

External steps that are not considered under building regulations should:

  • have a maximum rise of 220mm
  • have a minimum going of 220mm
  • be reasonably uniform.

A handrail should be provided where the total rise of a flight of external steps is more than 600mm and the going of individual steps is less than 600mm.

Guidance for the provision of handrails to steps that form an accessible approach can be found in supporting documents to building regulations.

10.2.6 Drives, paths and landscaping

Appropriate access (including private roads, shared private drives, private drives, car parking and paths) shall be provided to and around the home. Issues to be taken into account include:

a) general construction considerations
b) drainage
c) construction details
d) minimum sub-base thickness
e) house paths and patios

Homes should be provided with suitable access through the provision of private roads, shared private drives, private drives, car parking areas and paths, as appropriate.

General construction considerations

Private roads, shared private drives, private drives, car parking areas and paths should comply with relevant building regulations. Where abutting the home, they should be at least 150mm below the DPC, and laid to falls away from the home (unless a channel or other suitable means of collection and disposal is provided).

All vegetable matter should be removed from the area of the proposed works.

Only suitable fill material comprising clean, well-consolidated crushed rock, hardcore, slag or concrete should be used to make up levels.

Sub-bases should be mechanically consolidated in layers not exceeding 225mm.

Finished ground levels should be compatible with:

  • DPC levels
  • cover levels of drainage access points
  • depth of underground services (gas, electricity, water and drains)
  • adjacent surfaces

Private roads, shared private drives and private drives should:

  • be appropriate for the loads
  • provide reasonable access to and from a garage or car parking area
  • have a maximum gradient of 1:6
  • where the gradient is more than 1:10 and the gradient changes, have suitable transition lengths to reduce the risk of vehicles grounding.

Underground drainage or services that are below a private road, shared private drive, private drive, car parking area, path or patio should be protected against damage, as described in Chapter 5.3 ‘Drainage below ground’.

Edge restraint or kerbing should have a profile and foundation, which is suitable to form a permanent supporting edge for the expected vehicle loads on the road or drive.

Pedestrian access should be provided via a path within the curtilage of each home to the main entrance and the secondary entrance where present:

  • where entry to the home can be gained directly from a garage, a path to a secondary access door is not required
  • where the secondary entrance is to a mid-terrace home or ground floor flat, a path to a secondary access door is not required
  • where a garage, carport or car parking area is provided within the curtilage, a path should be provided to it from the home.

Where appropriate, a drive can be regarded as a path for the provision of access. Paths should have a maximum slope of 1:6. On steeper sloping ground, steps may be required.

Table 1: Suitable path widths

  • Within curtilage to main entrance, or any entrance designated by Building Regulations.
    • Minimum width of hard standing: 900mm
    • Minimum overall width: 900mm
  • Paths used for the removal of refuse to the collection point.
    • Minimum width of hard standing: 750mm
      Minimum overall width: 900mm
  • Paths adjoining a home (with hard standing 100mm or more from the wall of the home).
    • Minimum width of hard standing: 450mm
      Minimum overall width: 700mm
  • All other cases.
    • Minimum width of hard standing: 450mm
    • Minimum overall width: 600mm

HBBC Garden Drainage

Private roads, shared private drives and private drives should have adequate rainwater drainage and disposal.

Paved areas should:

  • have vertical alignment, finished levels, transition arrangements and gradients in accordance with the design
  • have surfaces with adequate falls, cross-falls and drainage to ensure that surface water is suitably drained
  • have sub-base levels with the same longitudinal gradient and cross-fall as the finished level
  • have surfaces not flatter than 1:40 or have a camber of 1:40 where no fall is available to avoid ‘flat spots’
  • have surfaces with a minimum finished fall of 1:80 where they form private drives and paths
  • drain away from the home (and garage), or drain to a channel or other suitable means of collection and disposal adjacent to the home
  • not drain surface water from private areas onto adopted areas
  • not be within 2m of a soakaway.

Where paving slabs are laid abutting drainage channels and gully grates, etc., the upper surface of the paving slab should be set approximately 5mm above the grating.

Where it is intended to use porous or permeable surfaces as part, or all, of the rainwater drainage system, reference should be made to CIRIA report C753 – The Sustainable drainage system (SuDS) manual.

Construction details

The construction of private roads, shared private drives, private drives and car parking areas should be constructed in accordance with the tables below and/or other published/approved design procedure.

Table 2a: Private road having frequent use by commercial vehicles

Table 2b: Shared parking and associated access areas having frequent use by commercial vehicles

Table 2c: Shared drives having infrequent use by commercial vehicles

Table 2d: Private drives and parking areas having use by cars and light vehicles

Notes

  1. In the first column, European harmonised names for the pavement layers are with the old UK designations included in brackets.
  2. Where a capping layer is specified, sub-base thickness can be reduced. Pavement Design CD 225 Revision 1 gives guidance on capping and sub-base thickness design based on CBR values with and without a capping layer.
  3. For the minimum thickness of the sub-base for different CBR values, refer to Table 3.
  4. Bond coat in accordance with BS 594987 should be applied to ensure effective bonding of the asphalt layers.
  5. Bituminous mixtures/asphalt can be used as a partial replacement of a full thickness granular sub-base type 1 material.
  6. If the binder course is subjected to an extensive period of trafficking before the surface course is applied, a recipe mixture containing a higher bitumen content will be more durable/resistant to fretting/ravelling under traffic.
  7. Where laid to either a 90 or 45 degree herringbone pattern, the edge perimeter should be laid with one single row of stretcher bond set parallel to the edge restraint. Where block pavers are laid abutting drainage channels, gulley grates, etc. the upper surface of the block pavers should be set 3-6mm above the grating. Manufacturer’s declared value markings W3 and S4 are acceptable. Where W3 is 1.0 kg/m2 or less and S4 is 45 or more based on ‘C scale unit’ (for abrasion, class A2 = maximum result is 23mm, class A1 = no performance determined).
  8. A 38mm thickness of graded 15/20mm unbound aggregate to BS EN 13242 (gravel), well rolled and compacted, should be used.
  9. Reference to clauses are in relation to the relevant European and/or British Standards.
  10. Asphalt contractors should be certified in accordance with the National Highway Sector Schemes for Quality Management in Highway Works – Scheme 16.

Minimum sub-base thickness

The thickness of any required capping layer and the sub-base should be determined after investigations and on-site tests have been carried out, with consideration to the:

  • CBR value
  • frost susceptibility of the sub-grade; where susceptible to frost, a suitable capping layer should be included below the sub-base to a suitable depth to ensure that the construction will not be affected by frost heave
  • granular sub-bases should be tested and certified as being non-frost susceptible and non-plastic.

Table 3: Minimum sub-base thickness for paved areas

CBR values

  • Less than 2%
    • Subgrade requires improvement(2)
  • 2-3%
    • 325mm minimum thickness of sub-base(1)
  • 3-5%
    • 250mm minimum thickness of sub-base(1)
  • 5-7%
    • 150mm minimum thickness of sub-base(1)
  • 7-20%
    • 100mm minimum thickness of sub-base(1)

(consolidated in accordance with MCHW Volume 1 clause 801, table 8/4)

Notes

  1. Minimum thickness of sub-base may be considered for reduction when using proprietary geogrid, provided they can be adequately justified and designed by an Engineer in accordance with Technical requirement R5.
  2. Specialist advice should be sort to improve the subgrade.

House paths and patios

The following construction will be generally acceptable for house paths and patios:

  • the sub-base comprising of a 100mm thickness of clean, non-frost susceptible well consolidated crushed rock, hardcore (maximum size 50mm), slag or concrete, the surface of which is blinded with 25mm of sand
  • paving slabs fully bedded in 25mm 1:4 cement/:sand mortar or a suitable alternative.

Concrete paths and patios should be not less than 75mm thick and have a tamped or textured finish. The concrete mix should be suitable to give a durable and frost resistant surface, as described in Chapter 3.1 ‘Concrete and its reinforcement’. Movement joints, not less than 10mm wide, should be provided across the full width of the path at not more than 4m centres. A movement joint is not required at the abutment with a wall unless the opposite edge of the concrete is also restrained.

10.2.7 Materials

Materials shall be suitable for their intended use. Concrete shall be of a mix design which will achieve sufficient strength for its purpose and be sufficiently durable to remain unaffected by chemical or frost action.

Sub-base material should be type 1 to clause 803 Table 8/2, MCHW Volume 1 SHW Series 800.

Hot rolled and mastic asphalts and macadam should comply with relevant standards, including:

  • BS EN 13108-1 ‘Bituminous mixtures. Material specifications. Asphalt Concrete’.
  • BS EN 13108-4 ‘Bituminous mixtures. Material specifications. Hot Rolled Asphalt’.
  • BS EN 13108-5 ‘Bituminous mixtures. Material specifications. Stone Mastic Asphalt’.
  • PD 6691 ‘Guidance on the use of BS EN 13108’.
  • BS 594987 ‘Asphalt for roads and other paved areas’.

Aggregates used in asphalt and macadam mixtures and unbound aggregate (graded 15/20mm gravel) for surfacing should comply with relevant standards, including:

  • BS EN 13043 ‘Aggregates for bituminous mixtures and surface treatments for roads, airfields and other trafficked areas’.
  • PD 6682-2 ‘Guidance on the use of BS EN 13043’.
  • BS EN 13242 ‘Aggregates for unbound and hydraulically bound materials’.
  • PD 6682-6 ‘Guidance on the use of BS EN 13242’.

Blocks, slabs, pavers, edgings, etc. should comply with relevant standards, including:

  • BS EN 771 ‘Specification for masonry units’.
  • BS EN 1344 ‘Clay pavers. Requirements and test methods’.
  • BS EN 1339 ‘Concrete paving flags. Requirements and test methods’.
  • BS 7533 ‘Pavements constructed with clay, natural stone or concrete pavers’.

Topsoil and subsoil should be of a quality that will not present a hazard to users of the garden area. BS 3882 (Topsoil), BS 8601 (Subsoil) and the Contaminated Land Exposure Assessment (CLEA) guidelines provide advice on determining the suitability of topsoil and subsoil.

10.2.8 Garden areas within 3m of the home

In order to provide for adequate access to and utility immediately around the home areas up to 3m from the habitable parts of the home shall not be waterlogged.

Waterlogging of garden areas within 3m of the habitable parts of the home should be prevented by appropriate soil selection and management, and if necessary, by drainage or other suitable means.

10.2.9 Garden areas

Garden areas within 20m of habitable accommodation shall be adequately prepared, stable and provided with reasonable access.

The stability of new or existing slopes in garden areas should be determined by an engineer in accordance with Technical Requirement R5. Alternatively, the following maximum gradients should apply:

  • unsupported granular soil should be 5° less than its natural angle of repose
  • unsupported cohesive soil should not exceed 9° (1:6).

Garden areas should have:

  • old foundations, concrete bases and similar obstructions removed from within 450mm of the finished ground surface
  • appropriate action, undertaken to restore physical condition (e.g. soil structure) and drainage characteristics of the topsoil and subsoil that has been compacted during construction. This should include subsoil decompaction, such as rotavating, to a minimum depth of 300mm and topsoil cultivation to the full depth of compaction. Further guidance is provided in BS 3882 on the depths, handling, management and preparation of topsoil and subsoil for landscaping.
  • ground disturbed during construction re-graded to conform to the general shape of the adjacent ground
  • a minimum thickness of 100mm topsoil provided
  • topsoil should be suitable for general landscape purposes and should also not contain contaminants which may present a hazard to the occupants
  • topsoil that is disturbed or compacted after placement should be fully reinstated before planting, turfing or seeding.

Subsoil should not be placed over topsoil. Construction rubbish and debris should be removed from the garden and other areas around the home before topsoiling, and before or after planting, turfing or seeding.

Access is not required to small isolated garden areas, such as narrow strips of land at the top or bottom of retaining walls, but should be provided to other areas where appropriate by steps or other suitable means.

10.2.10 Timber decking

Patios and decking shall be suitable for their purpose.

Timber decking, including support, should be naturally durable or treated with preservative to use Class 4 classification.

Decking that is more than 600mm above ground level should be:

  • in accordance with guidance published by the Timber Decking and Cladding Association (TDCA), or
  • designed by an engineer in accordance with Technical Requirement R5.

10.2.11 Landscaping

Planting shall be completed in a manner appropriate for the site conditions and layout. Possible future damage to the home caused by planting shall be minimised.

Where trees or shrubs have been removed, are to be retained or are to be planted by the builder, precautions should be taken to reduce the risk of future damage to homes and services in accordance with Chapter 4.2 ‘Building near trees’.