The NHBC Standards Chapter 5.1 – Substructure and Ground Bearing Floors offers comprehensive guidance on meeting technical requirements and recommendations for substructures, excluding foundations. This includes aspects such as substructure walls, ground-bearing floors with infill no deeper than 600mm, and the installation of services below the damp proof course (DPC). The chapter is designed to ensure structural integrity and safety, providing detailed standards that contribute to the creation of high-quality, durable buildings. Compliance with these guidelines is crucial for meeting NHBC’s minimum standards, which encompass design criteria, material specifications, and construction methods essential for the stability and performance of substructures and ground-bearing floors.
Key elements of Chapter 5.1 include strict adherence to the maximum depth of infill to prevent structural issues, the provision of clear and comprehensive design information, and ensuring proper load transfer to foundations. The chapter also emphasizes the importance of understanding ground conditions and appropriately managing services and drainage to maintain the integrity of the substructure. Furthermore, it addresses the preparation of ground below fill, selection of suitable fill materials, and the critical role of blinding in providing a stable base. By following these detailed guidelines, builders can achieve a robust and reliable substructure and ground-bearing floor system, ensuring long-term stability and performance of the buildings they construct.
5.1.1 Compliance
Substructures and ground-bearing floors must adhere strictly to the NHBC Technical Requirements to ensure structural integrity and safety. Compliance with these guidelines ensures that the construction meets the minimum standards set forth by the NHBC, which are designed to promote high-quality, durable, and safe buildings. Structures that follow the recommendations and specifications detailed in this chapter will generally be deemed acceptable by the NHBC, providing a benchmark for quality assurance. This includes adhering to design criteria, materials specifications, and construction methods that collectively contribute to the overall stability and performance of the substructure and ground-bearing floors.
One critical aspect of compliance is the restriction on the depth of infill. Floors must not exceed 600mm of infill depth to maintain structural stability and prevent undue settlement or movement. Exceeding this depth can compromise the load-bearing capacity of the floor and lead to potential structural issues. Therefore, ensuring that the infill depth remains within the specified limit is essential for meeting the NHBC standards.
5.1.2 Provision of information
Designs and specifications for substructures and ground-bearing floors must be produced in a clear and understandable format to ensure effective communication and execution. It is crucial that all relevant information is included in these documents and that they are distributed to appropriate personnel, including site supervisors, specialist subcontractors, and suppliers. This ensures that everyone involved in the construction process has access to the necessary details to perform their tasks accurately. The information provided should cover plan dimensions, levels related to benchmarks, the required sequence and depth of trench backfill, details of trench backfill, infill and void formers, and the work needed to maintain the integrity of DPCs and DPMs. Additionally, it should include details on proposed underground services, points of entry to the building, support for service penetrations through the substructure, and junctions between the DPM, DPC, and tanking.
Furthermore, the design and specification documents should detail underfloor, floor edge, and cavity insulation, as well as ground hazards and mitigation measures. This comprehensive provision of information ensures that the construction process can proceed smoothly, with each stage being clearly understood and correctly executed. By providing thorough and precise specifications, potential issues can be identified and addressed before they become significant problems, leading to a higher quality of construction and compliance with NHBC standards. Effective communication of this information also helps in coordinating various aspects of the project, ensuring that all parties are aware of their responsibilities and the overall project requirements, which ultimately contributes to the successful completion of the construction project.
5.1.3 Transfer of loads
Substructures and ground-bearing floors must be designed to ensure that loads are properly supported and transferred to the foundations or ground without causing undue movement. This requires a comprehensive understanding of the site conditions and careful planning during the design phase. The design must take into account findings from the site investigation, such as soil type, bearing capacity, and any potential ground hazards. Where the design necessitates infill deeper than 600mm, a suspended floor construction should be used instead of a ground-bearing slab. This is essential to avoid excessive settlement and ensure that the load is evenly distributed and adequately supported. Load-bearing partitions also require proper foundations and should not rely on ground-bearing floors for support, as this can lead to structural instability.
In regions like Scotland, special considerations are necessary for sleeper walls, which should not be built on ground-bearing floors. Instead, they require independent foundations to prevent undue stress and movement. The overall aim is to ensure that the substructure and ground-bearing floors can handle the imposed loads effectively, whether from the building itself or external factors such as soil movement and environmental conditions. By adhering to these guidelines, builders can mitigate the risk of structural failures and maintain the integrity of the building over its lifespan. Proper load transfer is crucial for the stability of the structure, and careful attention to design and construction details ensures that the building remains safe and durable.
5.1.4 Ground conditions
Substructures and ground-bearing floors must be designed with careful consideration of the ground conditions to ensure long-term stability and performance. Various factors such as ground hazards, bearing capacity, and the nature of the ground play a significant role in the design process. Ground hazards can include contaminated materials, waterlogged ground, and chemicals like sulfates, which can adversely affect the substructure and floors. It is essential to identify these hazards through thorough site investigations and implement appropriate mitigation measures, such as using protective layers or avoiding certain materials. The design must account for the bearing capacity of the ground to ensure that it can support the loads without excessive settlement or movement. In cases where the ground has variable bearing capacity or unstable soils, special measures like suspended floor construction may be necessary to maintain stability.
The nature of the ground also includes factors like shrinkable soil, expansive materials, and the effect of sloping ground on the substructure. Shrinkable soils, which contain a high percentage of fine particles and have a significant Modified Plasticity Index, can cause substantial movement and require specific design considerations. Suspended floors may be needed to manage these conditions effectively. Sloping ground can necessitate steps in the substructure and different floor levels, potentially requiring walls below DPC level to act as retaining walls. These walls must be designed by an engineer if the height difference (H) is greater than four times the thickness (T) or exceeds 1m. Additionally, construction activities on adjacent ground, such as ground treatment or infill surcharging, can impact the substructure and should be carefully managed to prevent damage. By addressing these various aspects of ground conditions, builders can ensure that the substructure and ground-bearing floors are robust, durable, and capable of withstanding the challenges posed by the site environment.
5.1.5 Services and drainage
Substructures and ground-bearing floors must be designed and constructed to adequately protect existing services and ground water drainage systems. This involves identifying and safeguarding all existing services before commencing construction work. It is essential to reconnect severed or disturbed ground water drains to a suitable outfall, particularly during dry periods when their activity might be less noticeable. The presence of active groundwater drainage must be retained to minimise flooding risks. Additionally, where existing services conflict with proposed foundations or substructure, appropriate measures such as protection, diversion, or concrete filling of remaining voids must be implemented. If services are no longer active and not needed, they should be disconnected and removed to avoid any future complications.
Furthermore, effective surface and subsoil drainage must be ensured on sites prone to waterlogging to maintain the integrity of the substructure. Retaining walls, for instance, may require land drains, hardcore fill, and suitable outlets to manage subsoil water collection. Ground or paths adjoining the home should slope away from the structure to ensure proper drainage, generally keeping at least 150mm below the DPC. The design should also include details for accommodating drainage and other services, ensuring flexible connections or other methods to handle differential movement. Pipes passing through substructure walls should be designed with adequate clearance or sleeves to prevent structural stress and accommodate movement, complying with manufacturer recommendations. These comprehensive measures ensure that the substructure and ground-bearing floors remain stable, functional, and free from water-related issues, safeguarding the building’s longevity and performance.
5.1.6 Ground below fill
The ground below fill must be adequately prepared to provide consistent and reliable support for the fill and the ground-bearing slab, ensuring stability and preventing undue movement. Proper preparation includes the removal of all topsoil containing vegetation and organic matter, such as tree roots, to create a clean and stable base. This preparation is crucial because organic materials can decompose over time, leading to voids and settlement issues. An even bearing surface is also essential to distribute the load evenly across the ground, preventing any differential settlement that could compromise the structural integrity of the floor slab. The suitability of the ground to support floor loads and any additional imposed loads must be thoroughly assessed to ensure it can handle the expected pressures without significant movement or deformation.
In cases where the ground is not naturally suitable, additional measures may be necessary to enhance its load-bearing capacity. This can include compacting the ground to increase its density and stability or using stabilisation techniques such as soil treatment or reinforcement. The use of geotextiles or other ground stabilisation materials can also be considered to improve the performance of the ground below the fill. Ensuring the ground is properly prepared not only supports the structural integrity of the ground-bearing slab but also contributes to the overall durability and performance of the building. By addressing these aspects during the preparation phase, builders can prevent future issues related to ground movement and ensure a solid foundation for the structure above.
5.1.7 Fill below floors
The fill material used below ground-bearing floor slabs must provide full and consistent support to ensure the stability and durability of the floor. This includes made ground, trench backfill, and infill, all of which should be placed and mechanically compacted in layers not exceeding 225mm to form a stable mass. Proper compaction is crucial as it eliminates voids and reduces the risk of future settlement, which can lead to uneven floors and structural issues. Where more than 600mm of infill is required at any point within a self-contained area, a suspended floor construction should be used instead of a ground-bearing slab. This is because deeper infill can compromise the load-bearing capacity of the floor, making it more susceptible to movement and settlement.
Concrete can be used as an alternative to backfill in trenches, offering a more stable and consistent support base. It is particularly useful in situations where the ground conditions or the nature of the fill material make it difficult to achieve the required compaction. The choice of fill material is also important; it must be free from hazardous materials, well-graded, and inert to avoid any adverse reactions or movements over time. The use of unsuitable fill materials, such as those containing organic matter, expansive clays, or chemicals, can lead to significant structural problems. By ensuring that the fill below floors is properly selected, placed, and compacted, builders can create a solid foundation that supports the ground-bearing floor slab effectively, maintaining the integrity and performance of the building.
5.1.8 Infill up to 600mm deep
Infill beneath ground-bearing floors must be carefully managed to ensure that it does not exceed a maximum depth of 600mm. This limitation is crucial because infill deeper than 600mm can lead to excessive settlement and instability of the floor slab. Ground-bearing slabs are only considered acceptable when the depth of infill is within this specified limit, as it ensures the loads imposed on the floor are adequately supported and distributed. Exceeding this depth necessitates the use of a suspended floor system, which is designed to be independent of the fill and capable of supporting itself and additional loads without relying on the compacted infill below. This approach helps mitigate risks associated with deeper infill, such as differential settlement and movement, which can compromise the structural integrity of the floor.
When the design requires more than 600mm of infill at any point within a self-contained area, the floor construction over the entire area must be adjusted to a suspended system. This system can effectively support self-weight, non-load-bearing partitions, and other imposed loads, ensuring overall stability. The use of a suspended slab becomes essential in such scenarios to avoid the negative impacts of deep infill, such as uneven settlement and potential damage to the structure above. By adhering to this guideline, builders can ensure that the ground-bearing floors perform as expected, providing a stable and reliable foundation for the building. Proper design and implementation of infill and suspended floor systems are critical to maintaining the safety and durability of the construction over its lifespan.
5.1.9 Materials used for fill
Materials used for fill beneath ground-bearing floors must be carefully selected to ensure they are suitable for their intended use, providing stable and consistent support. These materials should be well-graded, inert, and free from hazardous substances to avoid any adverse reactions or movements over time. Fill materials must be able to pass through a 150mm x 150mm screen in all directions to ensure uniformity and prevent large voids that could compromise the stability of the floor. Fill containing expansive materials, chemicals, or contaminants such as organic matter, demolition debris, furnace ashes, colliery shale, or slags should not be used unless they have been tested and deemed suitable by a qualified professional. Special attention should be given to sites with high water tables or wet conditions, where the use of materials like crushed or broken bricks must meet specific standards, such as the S1 designation according to BS EN 771.
When selecting fill materials, it is crucial to consider their source and consistency. If the material comes from a stable and uniform source, a single suitability check may suffice. However, if the material is variable or sourced from multiple locations, regular inspections and testing are necessary to ensure consistency and suitability. Industrial waste used as fill must undergo thorough testing to confirm its appropriateness. Material from stockpiles must be checked for uniformity, as different stockpiling methods can affect particle size and grading, with the outer layers potentially differing from unweathered material inside. By ensuring that fill materials are carefully selected, tested, and verified, builders can prevent issues related to settlement, contamination, and structural instability, thereby ensuring the long-term performance and durability of the ground-bearing floors.
5.1.10 Harmful or toxic materials
Harmful or toxic materials present in the fill or ground must be identified and managed to prevent adverse effects on the performance of the substructure and ground-bearing slab. These materials can include reactive substances, organic materials, toxic chemicals, sulfates, and substances that cause noxious fumes, rot, undue settlement, or damage to surrounding materials. Ensuring that the fill is free from these harmful substances is crucial to maintaining the structural integrity and safety of the building. If harmful levels of sulfate are detected, the construction must be adapted to resist sulfate attack. This can be achieved by using appropriate concrete mixes or protective barriers such as polyethylene sheets, which also serve as damp proof membranes (DPMs).
Testing for sulfate content and other harmful materials should be conducted by a suitably qualified person with detailed knowledge of the material and proposed conditions of use. Multiple samples may be required to accurately assess the characteristics of the fill material. In cases where harmful substances are unavoidable, the design of the substructure must incorporate measures to contain, resist, and prevent their adverse effects. This may involve using sulfate-resistant concrete blocks and mortar that comply with relevant standards such as BS EN 1996-1-1. By taking these precautions, builders can ensure that the substructure and ground-bearing slab remain durable and free from degradation caused by harmful materials, thereby protecting the long-term performance of the building.
5.1.11 Regulatory solutions
The use of recycled or secondary materials as fill must comply with relevant waste regulatory requirements to ensure environmental safety and compliance. Different regions have specific regulations governing the use of these materials. In England and Wales, materials used on the site of origin must follow the CL
Code of Practice, while materials transported to other sites require registration under a U1 exemption with the Environment Agency (EA) if less than 5000 tonnes. For quantities over 5000 tonnes, adherence to the WRAP protocol is necessary to ensure the material’s suitability and environmental compliance. In Northern Ireland and Scotland, any use of recycled materials requires registration under a paragraph 19 exemption with the respective environmental agencies (SEPA/NIEA).
Compliance with these regulatory solutions ensures that the use of recycled or secondary materials does not pose a risk to human health or the environment. The regulations are designed to promote the safe reuse of materials, reducing waste and encouraging sustainable construction practices. Builders must ensure that all regulatory requirements are met, including obtaining necessary permits and conducting appropriate testing to verify the material’s safety and suitability. By following these guidelines, builders can responsibly incorporate recycled materials into their projects, contributing to environmental conservation and sustainable development while maintaining the structural integrity and performance of the substructure and ground-bearing floors.
5.1.12 Walls below the DPC
Substructure and walls below the DPC (damp proof course) must be constructed to provide adequate support and durability, taking into account the need to resist moisture and maintain structural integrity. When walls act as temporary retaining structures, it is essential to place backfill in layers of equal thickness on both sides to prevent uneven pressure that could compromise the wall’s stability. If backfill is placed and compacted on one side before the other, the wall will function as a temporary retaining wall and should be designed by an engineer or constructed with a minimum thickness as specified in the guidelines. This ensures the wall can withstand the temporary condition without issues such as hydrostatic pressure causing failure.
Concrete cavity fill must maintain a minimum 225mm clear cavity below the DPC, which can be reduced to 150mm for specialised foundations, such as those used in timber-framed buildings, provided adequate drainage measures are implemented. This clear cavity helps prevent moisture from reaching the interior of the building, protecting the structure from damp-related issues. Walls below the DPC must also be resistant to frost action, sulfates, and other harmful materials. Proper design and construction of these walls, including the use of suitable bricks, blocks, and mortar, ensure they can support their intended loads and remain durable under various environmental conditions. By adhering to these guidelines, builders can create substructure walls that effectively manage moisture, provide necessary support, and contribute to the overall stability and longevity of the building.
5.1.13 Durability
Substructures and walls below the DPC (damp proof course) must be designed to support their intended loads while being resistant to environmental factors such as frost action, sulfates, and other harmful materials. The durability of these structures is paramount, as they form the foundation of the building and must withstand varying conditions over time. For brickwork, especially in the outer leaf below the DPC or in retaining walls, it is essential to use bricks that are durable and suitable for exposure to moisture and freezing conditions. Clay bricks should comply with BS EN 771 standards, classified according to their durability designation (F) and soluble salts content (S), ensuring they can resist freeze-thaw cycles and other environmental stresses.
Similarly, blockwork for use below the DPC must meet specific standards to ensure durability. Concrete blocks should have a minimum density of 1500 kg/m³ or a minimum compressive strength of 7.3 N/mm², as outlined in BS EN 771. Additionally, blocks made with sulfate-resisting cement or a higher than normal cement content may be necessary to combat sulfate attack in certain ground conditions. Ensuring the suitability of bricks and blocks involves consulting manufacturers and obtaining written confirmation of their performance in the given geographical location and structural application. By adhering to these specifications, builders can create substructures and walls that maintain their integrity and durability under adverse conditions, ensuring the longevity and safety of the building.
5.1.14 Mortar
The mortar used in substructures and walls below the DPC must be suitable for the specific location and intended use, taking into account the type of masonry units and their exposure to environmental conditions. The selection of mortar should follow the recommendations given in BS EN 1996-1-1, ensuring it provides adequate strength and durability. Mortar mixes must be designed to match the strength and type of masonry, whether it be clay bricks, concrete blocks, or other materials. Proprietary mortars and admixtures can be used, provided they are compatible with the masonry units and applied in accordance with the manufacturer’s guidelines.
In areas where sulfates are present in the ground, ground water, or masonry, sulfate-resisting cements should be used to prevent chemical degradation of the mortar. These cements, compliant with BS EN 197, offer enhanced durability in sulfate-rich environments. The proper use of sulfate-resistant mortar ensures that the structural elements remain intact and free from damage caused by chemical reactions. By carefully selecting and applying the appropriate mortar mix, builders can enhance the performance and longevity of substructures and walls below the DPC, ensuring they remain robust and capable of supporting the building’s loads without succumbing to environmental stresses.
5.1.15 Wall ties
Wall ties used in substructures and walls below the DPC must be suitable for their intended purpose, ensuring structural stability and integrity. These ties, which must comply with BS EN 845-1 or be assessed according to Technical Requirement R3, are crucial for maintaining the connection between different layers of masonry and preventing separation under load. Properly installed wall ties help distribute loads evenly and accommodate any differential movement between the masonry layers, reducing the risk of structural failure. The spacing of wall ties, both vertically and horizontally, should be compatible with the insulation batts or slabs used below and above the DPC, ensuring continuous support and stability.
In addition to their primary structural role, wall ties must also be resistant to corrosion and environmental degradation, especially in areas exposed to moisture and aggressive ground conditions. Using corrosion-resistant materials, such as stainless steel, can significantly extend the lifespan of wall ties and maintain the integrity of the masonry structure. Proper installation practices, including ensuring adequate embedment and alignment of the ties, are essential to their performance. By selecting and installing the right wall ties, builders can ensure that the substructures and walls below the DPC remain securely bonded and capable of withstanding the loads and environmental conditions they will encounter over the building’s lifetime.
5.1.16 Blinding
Blinding is an essential process in substructure construction, providing a suitable surface for materials placed above it. The primary purpose of blinding is to create a smooth, stable base for subsequent layers, such as concrete slabs or damp proof membranes (DPMs). This involves spreading a thin layer of material, such as sand, fine gravel, or concrete, over the surface of the fill or ground. Proper blinding helps to prevent the migration of fines from the fill into the concrete, which can cause voids and weaken the structure. It also ensures that the DPM is not punctured by sharp objects, maintaining its integrity and effectiveness in preventing moisture ingress.
In some cases, concrete blinding may be necessary, particularly when there are significant voids in the fill material that could lead to the loss of fines. Concrete blinding provides a more robust and even surface, which is crucial when reinforcement is used in the ground floor slab. The firm and level base provided by concrete blinding helps to support the reinforcement and maintain the design cover, ensuring the structural integrity of the slab. By implementing appropriate blinding techniques, builders can ensure a solid foundation for the floor slab and other structural elements, enhancing the overall durability and performance of the building.
5.1.17 Ground floor slab and concrete
Ground-bearing floors must be constructed with adequate strength and durability, using concrete mixed and reinforced appropriately to support floor loads safely and resist chemical and frost action. The concrete used for ground-bearing slabs should be at least 100mm thick, including any monolithic screed, to provide sufficient structural capacity and longevity. This thickness ensures that the slab can handle the imposed loads, including those from the building and any additional elements like furniture and occupants, without excessive deflection or cracking. The concrete mix should be designed to meet the specific requirements of the site, considering factors such as load-bearing capacity, exposure conditions, and potential chemical reactions.
In addition to strength, the ground floor slab must be durable enough to withstand environmental conditions, such as freeze-thaw cycles and exposure to aggressive chemicals in the ground. This may involve using specific types of concrete or additives to enhance the slab’s resistance to these conditions. Reinforcement, such as steel mesh or rebar, should be used where necessary to provide additional strength and control cracking. Proper curing of the concrete is also crucial to achieve the desired properties and prevent premature deterioration. By ensuring that the ground floor slab is designed and constructed with these considerations in mind, builders can create a robust and long-lasting foundation that supports the overall stability and performance of the building.
5.1.18 Laying the ground-bearing floor slab
Laying the ground-bearing floor slab requires careful attention to detail to ensure that the finished floor is level, durable, and effectively impervious to moisture. Before pouring the concrete, all underfloor services and ducts should be installed and tested to prevent any issues after the slab is in place. This includes plumbing, electrical conduits, and any other utilities that need to run beneath the floor. Proper planning and coordination are essential to ensure that these services are correctly positioned and secure. The DPM must be intact and correctly positioned to link with the wall DPCs, forming a continuous barrier against moisture ingress. Special care should be taken to protect the DPM during concrete pouring to avoid damage.
During the actual laying of the slab, the concrete should be poured and levelled carefully to achieve a smooth, even surface. This involves using appropriate tools and techniques to spread, compact, and finish the concrete, ensuring that it meets the required specifications for flatness and levelness. Proper curing is critical to developing the full strength and durability of the concrete, preventing issues such as cracking and surface defects. Protecting the slab from adverse weather conditions and maintaining adequate moisture levels during curing can significantly enhance the quality and performance of the finished floor. By following these best practices, builders can ensure that the ground-bearing floor slab provides a stable, level, and moisture-resistant base for the building, contributing to its overall durability and functionality.
5.1.19 Damp proof course
The damp proof course (DPC) is a critical component in preventing moisture from penetrating into the building’s interior, and it must be carefully positioned and installed to be effective. The DPC should be positioned at least 150mm above the external finished ground or paving level to prevent moisture from bridging into the structure. This elevation ensures that rain splash and rising damp do not compromise the integrity of the building. Additionally, the DPC must be linked with any damp proof membrane (DPM) to create a continuous barrier against moisture. The correct width of the DPC must be fully bedded and either welded or lapped by at least 100mm to maintain its impermeability.
On sloping sites, stepped DPCs may be necessary to accommodate changes in ground level. It is crucial to ensure that these stepped DPCs and DPMs are properly linked so that every part of the building is protected from moisture ingress. The materials used for DPCs must be suitable for the specific conditions they will face. Acceptable materials include bitumen-based products, polyethylene, and proprietary materials that comply with Technical Requirement R3. These materials must be durable, flexible, and capable of withstanding the environmental conditions to which they will be exposed. By following these guidelines, builders can ensure that the DPC effectively protects the building from moisture, thereby preserving the structural integrity and comfort of the interior spaces.
5.1.20 Damp proofing concrete floors
Ground-bearing concrete floors must be effectively damp proofed to prevent moisture from penetrating into the home. This is typically achieved by providing a continuous damp proof membrane (DPM) beneath the concrete slab. The DPM should have sealed laps of at least 300mm wide and be linked with the wall DPCs to form an unbroken barrier against moisture. This barrier is essential for maintaining a dry and healthy indoor environment, as it prevents ground moisture from rising through the floor and into the living spaces. When the DPM is located below the slab, a blinding layer of sand is recommended to fill voids in the hardcore and minimise the risk of puncturing the membrane.
Maintaining a clear cavity of at least 225mm below the DPC is necessary to ensure proper drainage and moisture control. For specialised foundations, such as those used in timber-framed buildings, this depth may be reduced to 150mm, provided that adequate weepholes and drainage measures are in place. On sloping sites, the DPCs and DPMs must be carefully linked to protect all parts of the building. Suitable materials for DPMs include 1200 gauge polyethylene sheets, bitumen sheets, and other compliant materials. Proper installation of the DPM, including trimming and sealing, ensures that the ground-bearing floors are resistant to moisture ingress, thereby protecting the building’s structure and maintaining a comfortable living environment.
5.1.21 Thermal insulation
Thermal insulation in ground-bearing floors and walls below the DPC is essential to comply with Building Regulations and to provide energy efficiency and comfort within the home. The insulation materials used must be suitable for their intended location, with properties such as appropriate density and low water absorption. Insulation placed below ground-bearing slabs should also be resistant to ground contaminants to ensure long-term performance. Common materials for floor insulation include expanded polystyrene boards (grade EPS 70) that comply with BS EN 13163 and other proprietary materials that meet Technical Requirement R3. Properly installed insulation helps to reduce heat loss through the floor, contributing to lower energy costs and a more comfortable indoor environment.
In addition to floor insulation, wall insulation is critical to prevent thermal bridging, particularly at junctions between floors and external walls. Cavity insulation materials, super lightweight blocks, or blocks with face-bonded or integral insulation should be used to meet performance standards. The thickness of these materials should be chosen based on the required thermal performance. Design considerations must also include extending cavity insulation below the floor slab level, linking floor and wall insulation, and providing perimeter insulation to floors. Addressing thermal bridging effectively reduces heat loss and prevents cold spots, which can lead to condensation and mould growth. By ensuring comprehensive thermal insulation, builders can enhance the energy efficiency and comfort of the building, meeting regulatory requirements and promoting sustainable living.
5.1.22 Installation of insulation
The installation of thermal insulation in ground-bearing floors must be executed with precision to ensure the full thermal performance of the floor is achieved. Insulation boards should be tightly butted together to eliminate gaps, which can significantly reduce the effectiveness of the insulation by allowing cold air to penetrate through. This continuity of insulation is crucial for maintaining consistent thermal protection across the entire floor area. Additionally, when insulation is turned up vertically at the edges of the slab, it must be protected during the pouring and tamping of concrete to prevent damage and displacement. This can be achieved by using protective boards or similar measures to shield the insulation from mechanical impacts.
Proper installation also involves careful planning and coordination with other building elements, such as the damp proof membrane (DPM). The DPM should be correctly positioned to avoid bridging cavities and creating thermal bridges, which can undermine the insulation’s effectiveness. Any joints or penetrations through the insulation, such as pipes or ducts, should be sealed to prevent air leakage. Ensuring that the insulation is installed according to the manufacturer’s specifications and relevant building codes not only maximizes energy efficiency but also contributes to the overall durability and performance of the building. By adhering to these best practices, builders can achieve optimal thermal insulation, leading to lower energy costs and enhanced comfort for occupants.
5.1.23 Further information
For additional guidance on substructures and ground-bearing floors, reference materials such as BRE Digest 433 offer valuable insights and recommendations. This document provides in-depth information on various aspects of construction, including detailed explanations of standards and best practices. It serves as a useful resource for builders, designers, and engineers seeking to enhance their understanding and implementation of effective substructure and flooring solutions. By consulting such resources, construction professionals can stay informed about the latest industry developments and ensure compliance with relevant regulations and standards.
The figure reference table at the end of the chapter offers a visual aid to complement the textual guidance provided in the standards. Figures such as those illustrating the substructure on sloping ground, diversion of existing services, and installation details for pipes and insulation, provide clear examples of how to apply the guidelines in practical scenarios. These visuals help to clarify complex instructions and ensure that construction practices are carried out correctly. By utilizing both textual and visual resources, builders can achieve a more comprehensive understanding of the requirements and best practices for constructing substructures and ground-bearing floors, leading to higher quality and more reliable building outcomes.
