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Unveiling the Role of a Residential Structural Engineer

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In the realm of architecture, where form meets function, the presence of a Structural Engineer becomes indispensable. Just as an architect brings dreams to life through design, a Structural Engineer ensures that those dreams stand the test of time. Within the vast spectrum of engineering disciplines, encompassing everything from tunnels to turbines, bridges to boardrooms, resides the residential Structural Engineer – the unsung hero who collaborates with architects to shape the built environment we call home.

Arches House, West Hampstead, NW London - structural installation
Arches House, West Hampstead, NW London – structural installation

When it comes to your residential extension project, the Structural Engineer plays three pivotal roles, each contributing to the success and integrity of the final design.

Structural Surveys and Inspections: Peering into the Soul of Your Home

At the outset, the Structural Engineer conducts a thorough structural survey – an examination that scrutinises the property’s structural soundness without invasive measures. This survey serves as a prerequisite for calculating the new extension’s structural requirements. While some engineers may skip this step and rely on assumptions, it is imperative to understand why such an approach is not recommended, as we will explore later.

Distinct from surveys, structural inspections are conducted when the Engineer needs to gather additional information that could not be obtained during the initial survey. These inspections involve invasive investigations, venturing beneath floors, behind walls, within ceilings, and beneath the ground. Through this meticulous examination, the Engineer aims to identify acute or potential breaches in structural integrity in specific areas around the property

Herbert Paradise, Kensal Rise, NW London - installation of structure
Herbert Paradise, Kensal Rise, NW London – installation of structure

Structural Calculations: Unleashing the Power of Mathematics

Construction is an intricate dance of load-bearing elements designed to transmit forces from the roof to the footings safely. The structural integrity of a building defines its ability to fulfill this fundamental function without compromising its form or stability. Structural calculations, the mathematical backbone of the Engineer’s work, serve as a set of proofs that outline how the new space will open up and guide the construction of the extension while preserving the structural integrity of the existing property.

These calculations delve into the nitty-gritty details of construction, such as foundation type and depth, concrete strength, steel beam type and sizing, connection details, support over openings, loading onto internal walls, spreader plate type and size, joist sizing, spans, distances, joist hangers, trimmer details, and fixing methods. Through a meticulous analysis of these factors, the Engineer harnesses the power of mathematics to determine the optimal structural design for your extension

Structural Design: Merging Form and Function

Armed with the insights and data gleaned from the calculations, the Structural Engineer proceeds to generate the structural design—a tangible manifestation of the intricate details that underpin the construction process. This design overlays the approved architectural plans, showcasing how the structure will be assembled and integrated into the overall project.

The integration of the structural design with the approved plans can be approached in two ways. Either the Architect assimilates the structural work into the existing plans, or the Engineer creates separate drawings that incorporate the structural design. Regardless of the approach, the key is to ensure that the structural design seamlessly aligns with the planning-approved drawings. This harmonization allows you, as the homeowner, to enjoy the clarity and simplicity of a unified set of plans, alleviating any confusion or concerns that may arise from disparate documents.

Now that we have unveiled the essential roles of a residential Structural Engineer in the context of extensions, it is crucial to understand why the early-stage surveys and inspections are not mere formalities to be skipped. By embarking on a non-invasive survey, the Engineer gains valuable insights into the existing structure, allowing for a holistic understanding of the project. Relying on assumptions alone can lead to erroneous conclusions and jeopardise the integrity of the extension, putting your investment and safety at risk.

Ice Cream House, Hampstead, North London - replacement of existing timber floor joists and stairs
Ice Cream House, Hampstead, North London – replacement of existing timber floor joists and stairs

In conclusion, the contributions of a residential Structural Engineer are instrumental in the success of your extension project. Through thorough surveys and inspections, they unravel the secrets of your home’s structure, ensuring a solid foundation for the design process. The calculated structural proofs provide the roadmap for the construction, while the resulting structural design brings form and function into perfect harmony. By embracing the expertise of a Structural Engineer, your journey toward a beautiful, sustainable, and structurally robust extension can proceed with confidence and peace of mind.

If you would like to talk through your project with the team, please do get in touch at mail@risedesignstudio.co.uk or give us a call on 020 3290 1003

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The Importance of Opening Up Works: House Extensions

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As an architect practice with over 40 years of combined experience, we have come to realise the importance of opening up works when it comes to drawing up structural designs for a house extension. These works not only minimise guesswork but also provide a solid baseline for understanding the existing structure of the building, allowing us to plan and execute the new space safely and efficiently.

Herbert Paradise, Kensal Rise, NW London – trial pit to review the ground condition and extent of existing foundations of the house as well as the neighbour’s house

When it comes to structural investigations, it is not uncommon for the Structural Engineer to make assumptions about the building before crunching the numbers of the structural design. However, relying solely on assumptions carries significant risks. Therefore, whenever possible, it is preferable to carry out opening up works as a means of gathering concrete information about the structure, ensuring that the design process is based on accurate data rather than guesswork.

Arches House - opening up works to reveal ground conditions and extent of existing foundations
Arches House, West Hampstead, NW London – trial pit (opening up works) to reveal ground conditions and extent of existing foundations

Opening up works are typically requested by the Structural Engineer, and sometimes the Architect, when there is a need for further investigation of the building’s structure. These works involve carefully stripping away precise surface areas to reveal specific sections of the underlying structure that the Structural Engineer needs to physically inspect before producing a suitable structural design for the extension.

There are four common types of opening up works that are often carried out for extensions:

  1. Trial pits: These are holes, usually measuring around 1 square meter, that are excavated by hand and positioned adjacent to the outside wall of the building. The purpose of trial pits is to check the depth and type of foundations that the building sits upon, providing essential information for the design process.
  2. Lifting floorboards: This type of opening up work is performed to investigate various aspects, such as the continuity of suspected load-bearing walls, the condition of dwarf walls, joist integrity, and water table saturation. It is crucial to minimise the disturbance to the flooring and only remove the necessary sections for inspection.
  3. Boarded attics: Attic spaces are sometimes boarded over, and these boards may need to be removed to assess the presence of voids behind or beneath them, as well as to check the direction and sizing of joists. Fortunately, the advent of keyhole cameras has allowed us to minimise disruption during this process.
  4. Exposing walls and ceilings: In some cases, sections of plastered walls and/or ceilings need to be removed to inspect the presence of supporting members, such as reinforced steel girders. Additionally, exposing walls and ceilings allows us to check for the existence of spreader plates supporting the girders, the integrity of the supporting wall, and the nature and quality of any connections.

When carrying out opening up works for an extension, it is best practice to have the instructing Structural Engineer present along with the tradesmen. This ensures that the tradesmen can work under the direct instruction of the Structural Engineer and allows for real-time inspections. By being present on-site, the Structural Engineer can inspect the exposed areas firsthand, avoiding the need to rely solely on photographs. Moreover, this approach holds the Structural Engineer accountable for the work they produce and ensures that their expertise is fully utilised.

Herbert Paradise, Kensal Rise, NW London - opening up works in the ceiling to reveal joist directions
Herbert Paradise, Kensal Rise, NW London – opening up works in the ceiling to reveal joist directions

To minimise disruption, it is important to keep the size of the openings as lean as practicable. Additionally, any necessary making-good should ideally be completed on the same day, immediately after the inspection. This helps to maintain the project’s momentum and ensures that the opening up works do not cause unnecessary delays.

Undoubtedly, carrying out opening up works for an extension can be a logistical challenge and may cause temporary inconveniences. However, the benefits of doing so far outweigh the temporary disruptions. These works allow the Structural Engineer to accurately baseline the makeup of the building, providing vital information for designing an optimally structured extension. By avoiding assumptions and relying on concrete data, we can create designs that are not only safe but also efficient and sustainable, aligning with our studio’s focus on low energy and low embodied carbon designs.

In conclusion, when embarking on a house extension project, it is essential to prioritise opening up works. These works serve as a critical step in the design process, allowing us to understand the existing structure, identify potential issues, and develop an extension that seamlessly integrates with the building. By investing in opening up works, we can ensure that our designs are not only beautiful but also structurally sound, energy-efficient, and environmentally conscious. So, embrace the process, trust in the expertise of your Structural Engineer, and unlock the true potential of your home with a well-planned and thoughtfully executed house extension.