CSMANLTD provides specialist basement construction services in Hackney for homeowners, developers and commercial clients looking to create additional usable space below existing buildings.
Basement construction requires careful consideration of excavation, foundations, ground conditions, structural stability, groundwater, drainage and neighbouring properties. In Hackney, local planning and environmental considerations also need to be taken into account, particularly where basement development affects gardens, lightwells, drainage or surrounding properties.
Our team provides a range of below-ground construction services, including basement excavation, underpinning, piling, deep foundations, reinforced concrete structures, structural works, waterproofing and drainage.
Whether you are considering a new basement beneath an existing house, a garden basement, a basement extension or the conversion of an existing cellar, CSMANLTD can develop a construction approach based on the requirements of your property.
Constructing a basement beneath an existing property is a complex structural project. The excavation can extend below existing foundations and may take place close to neighbouring buildings, roads, trees, utilities and drainage infrastructure.
Before construction begins, the site needs to be assessed to understand the existing structure, foundation arrangements, ground conditions and proposed basement design.
CSMANLTD takes an engineering-led approach to basement construction. Our team can coordinate excavation, temporary works, underpinning, structural construction, waterproofing and drainage as part of a single construction strategy.
With more than 10 years of practical experience in groundworks, piling, deep foundations, underpinning and basement construction, CSMANLTD provides construction solutions for residential and commercial projects across London.
Our basement services can be adapted to different property types, site conditions and project requirements.
New Basement Construction
We construct new basements beneath existing buildings and within suitable external areas.
The construction process can include excavation, temporary support, foundations, reinforced concrete walls and slabs, structural works, waterproofing and drainage.
The appropriate construction method depends on factors such as the basement depth, site access, existing foundations, ground conditions and neighbouring structures.
Under House Basement Construction
Building a basement underneath an existing house requires careful control of excavation and structural support.
Where the proposed basement extends below existing foundations, underpinning or another engineered foundation solution may be required.
CSMANLTD can coordinate underpinning, excavation and structural construction to help maintain the stability of the existing property during the project.
Garden Basement Construction
A basement may also be constructed beneath a suitable garden or external area.
Garden basement projects can provide additional internal floor space without extending the main building above ground. However, the impact on gardens, trees, drainage, biodiversity and the surrounding environment needs to be considered.
Hackney’s residential planning guidance specifically recognises that basement excavation and lightwells can affect front gardens, visual appearance, biodiversity and surface water runoff.
Basement Excavation
Basement excavation involves removing soil and other ground materials to create the required underground space.
The excavation method must account for the depth of the proposed basement, ground conditions, access restrictions and the structural requirements of the existing building.
Where required, temporary support and underpinning can be incorporated into the excavation sequence.
Basement Extension and Conversion
If you already have a basement or cellar, we can help improve, extend or convert the existing space.
Depending on the property, the work may involve lowering the existing floor, increasing the basement footprint, strengthening foundations, improving waterproofing or installing new drainage systems.
Each existing basement is different, so the appropriate construction method should be established after assessing the property.
Underpinning for Basement Construction in Hackney
Underpinning can be required when basement excavation takes place beneath or close to existing foundations.
The appropriate underpinning method depends on the existing building, foundation depth, soil conditions, structural loads and proposed excavation.
CSMANLTD provides underpinning and foundation solutions as part of its wider basement construction capability.
The work is carefully planned so that excavation, temporary support and permanent structural works are completed in an appropriate sequence.
Basement Structural Engineering and Groundworks
Basement construction involves several interconnected structural and groundworks activities.
Our capabilities include:
By coordinating these elements, we can develop a construction approach around the actual requirements of the property.
Basement Waterproofing and Drainage in Hackney
Water management is a key consideration for any basement project.
A basement sits below ground level and therefore requires appropriate protection against water ingress. Waterproofing and drainage need to be considered during the design and construction stages rather than after the structure has been completed.
The appropriate waterproofing system depends on ground conditions, groundwater, basement construction, intended use and engineering requirements.
CSMANLTD can coordinate waterproofing and drainage as part of the basement construction process, including drainage channels, sump systems and pumping arrangements where appropriate.
Planning Considerations for Basement Construction in Hackney
Hackney has specific planning guidance for residential extensions and alterations, including basement development.
Hackney’s Residential Extensions and Alterations Supplementary Planning Document was adopted in December 2025 and came into effect in January 2026. The document provides current guidance for homeowners, architects and developers and includes a dedicated section covering basements.
The council’s guidance highlights the potential impact of basement excavation on the appearance of a property and street scene, particularly where a new lightwell is proposed. It also identifies potential effects on garden space, trees, biodiversity and water runoff.
Planning requirements can vary depending on the property, proposed works and location. Hackney advises applicants to check the planning information relevant to their individual property, including conservation areas, listed buildings, Tree Preservation Orders and Article 4 Directions.
This makes early assessment important before construction work begins.
Basement Development and Flood Risk in Hackney
Flood risk and drainage are important considerations when developing basements in Hackney.
Hackney’s planning policy states that development involving the creation or extension of basements must not increase the potential for groundwater flooding. The council also identifies requirements relating to flood risk assessments and sustainable drainage in critical drainage areas.
Hackney is exposed to different forms of flood risk, including river and surface water flooding. The council maintains strategic flood risk information and advises that flood risk should be considered when planning development and building works.
For this reason, basement projects should consider groundwater, surface water, drainage and flood risk during the early design stages.
Basement Impact and Structural Considerations in Hackney
A basement project can affect more than the property being developed.
Excavation may influence neighbouring buildings, existing foundations, retaining structures, drainage systems and underground infrastructure.
The technical assessment for a basement project may therefore need to consider:
The exact technical information required will depend on the nature and location of the proposed development.
Basement Construction and Lightwells in Hackney
Lightwells can provide natural light and ventilation to basement accommodation, but their design can also influence the appearance and functionality of the property.
Hackney’s residential guidance notes that lightwells can have a visual impact, particularly where they result in significant loss of front garden space. The council encourages proposals to consider the existing character of the street and the relationship between the building and its garden.
A basement design should therefore consider the lightwell alongside the wider basement structure rather than treating it as a separate feature.
Basement Construction for Hackney Properties
Hackney includes a wide range of residential properties, conservation areas and established neighbourhoods. Basement construction can therefore present different challenges from one site to another.
Some projects may involve excavation beneath an existing house, while others may involve a garden or external basement. Restricted access can also influence the choice of excavation and construction methods.
Before construction begins, we consider factors including:
The construction methodology can then be developed around the specific property.
Choosing an experienced contractor is important because basement construction combines excavation, structural engineering, foundations, waterproofing and drainage.
More than 10 years of construction experience
CSMANLTD has practical experience across groundworks, piling, deep foundations, underpinning and basement construction.
Integrated construction services
Our capabilities cover excavation, underpinning, piling, foundations, structural construction, waterproofing and drainage.
Engineering-led approach
We consider structural stability, ground conditions and construction sequencing before excavation begins.
Residential and commercial experience
We work with homeowners, developers and commercial clients on different types of below-ground construction projects.
Practical construction solutions
Every property has different ground, access and structural conditions. We develop the construction approach around the individual site.
London construction experience
Our team understands the challenges associated with basement construction in dense urban environments where neighbouring properties and restricted access need to be considered.
Site Assessment
We begin by reviewing the property, existing structure, foundations, site access and proposed basement requirements.
Feasibility and Engineering
The proposed excavation and structural requirements are assessed to identify a suitable construction strategy.
Planning and Technical Preparation
Relevant planning requirements, local restrictions, structural information, drainage and flood risk considerations are reviewed before construction.
Excavation and Temporary Works
Excavation is undertaken using a controlled methodology appropriate to the site and structural requirements.
Underpinning and Foundation Works
Where required, underpinning, piling or other foundation solutions are completed to support the existing building and proposed basement.
Basement Structure
The basement structure is constructed using the specified structural system, which may include reinforced concrete walls, floors, slabs and structural steelwork.
Waterproofing and Drainage
Waterproofing and drainage systems are installed to protect the basement and manage water effectively.
Completion
The completed basement is prepared for its intended use, whether that is living accommodation, a home office, gym, entertainment area, storage or another suitable purpose.
Basement Construction for Homeowners and Developers
A basement can provide valuable additional floor space without increasing the height or footprint of a property in the same way as some above-ground extensions.
For homeowners, basement space can be used for a home office, gym, guest area, entertainment room, utility space or other practical purposes.
For developers, basement construction can form part of a larger residential or commercial project. CSMANLTD can provide excavation, piling, underpinning, foundations and structural construction as part of the wider development.
The suitability of basement construction depends on the individual site, planning requirements, structural design and ground conditions.
Start Your Basement Project in Hackney
If you are considering basement construction in Hackney, an early assessment can help establish the technical and planning considerations associated with the project.
CSMANLTD can assist with basement excavation, underpinning, piling, foundations, structural construction, waterproofing, drainage and associated groundworks.
Planning requirements depend on the proposed development and the property. Hackney advises property owners to check the planning requirements relevant to their individual site, including conservation areas, listed buildings and Article 4 Directions.
Yes. Hackney adopted its updated Residential Extensions and Alterations SPD in December 2025, which came into effect in January 2026 and includes specific guidance covering basements.
Issues can include the appearance of the property and street, garden space, lightwells, trees, biodiversity, drainage, flooding and the impact of excavation. Hackney’s guidance specifically highlights these considerations for basement development.
An under-house basement can be possible depending on the property, structural condition, foundation arrangement, ground conditions and planning requirements. Underpinning or another engineered foundation solution may be required.
Garden basement construction may be possible where the property and proposal meet the relevant planning and technical requirements. The impact on garden space, trees, biodiversity, drainage and surrounding properties should be considered.
Not every project requires underpinning. It depends on the relationship between the proposed excavation and the existing foundations. A structural assessment should determine the appropriate foundation solution.
Yes. Hackney planning policy states that basement creation or extension must not increase the potential for groundwater flooding. Flood risk and sustainable drainage may also need to be considered depending on the site.
Lightwells can form part of a basement design where appropriate. However, Hackney’s guidance highlights their potential impact on front gardens, street appearance and water runoff, so their design needs to be carefully considered.
The waterproofing system depends on the basement structure, ground conditions, groundwater and intended use. Suitable systems can include waterproof concrete, membranes, drainage channels and sump pump arrangements.
There is no standard price because every basement project is different. Costs depend on factors such as basement size, excavation depth, access, ground conditions, existing foundations, underpinning, structural works, waterproofing and drainage.
The construction period depends on the size and complexity of the project, excavation requirements, structural works, access and the required planning and technical approvals. A project-specific programme can be prepared following an assessment.
Yes. Older properties require careful consideration of existing foundations, structural condition and neighbouring buildings before excavation. The construction method can then be developed around the property’s specific requirements.
Yes. Where required, basement excavation and underpinning can be coordinated as part of the same construction project.
Yes. Basement drainage can be incorporated into the construction strategy. The appropriate solution depends on groundwater, surface water, site conditions and the basement design.
Yes. CSMANLTD works with residential homeowners, developers and commercial clients. Our capabilities include excavation, piling, underpinning, foundations and structural construction.
CSMANLTD combines practical construction experience with groundworks and engineering capabilities. Our services include excavation, underpinning, piling, foundations, structural works, waterproofing and drainage, allowing the different elements of a basement project to be coordinated through one construction team.
TESTIMONIALS
We hired CSMANLTD to design and build a basement under our family home, and the entire process was seamless. Their team took care of everything—from underpinning and excavation to drainage and structural integrity—offering expert advice at every stage. The project was completed on time and within budget. We now have a stunning living space that has transformed our home. Highly recommend their design and build service!
construction worker
CSMANLTD has become our go-to partner for pre-construction groundwork and basement development. Their in-house engineering team provides invaluable insight during the early stages, allowing us to begin on-site work while final designs are being approved. Their ability to handle piling, deep excavations, and below-ground utilities has saved us significant time and cost across multiple projects. A truly unique and reliable approach to construction.
construction worker
We collaborated with CSMANLTD on a mixed-use development requiring complex temporary works and deep foundation solutions. Their expertise in structural engineering and piling was evident from day one. They delivered a robust, cost-effective design-build solution that kept the project on track. Safety was a top priority on site, and their team operated with professionalism throughout. A standout contractor in the industry.
construction worker
As architects, we value contractors who understand both design intent and structural feasibility. CSMANLTD bridges that gap perfectly. Their in-house engineers work closely with our team to optimise structural frames, foundations, and basement construction—often suggesting innovative, cost-saving alternatives without compromising safety. They are a true extension of our professional team.
construction worker
Our Victorian house had foundation issues and limited space. CSMANLTD assessed the structure, recommended underpinning, and constructed a full basement beneath our garden—maximising space without affecting the main house. The work was clean, safe, and incredibly well-managed. Now we have a gym, cinema room, and extra bedroom. We couldn’t be happier with the result.
construction worker
