Are you removing an external load bearing wall or an internal wall?
While most modification work is fairly quick and simple to achieve, things can become more complex if your plans include knocking down an external load bearing wall or removing internal walls.
These links are referenced in the diagram above:
Find out about planning rules, permitted development limits and building regulations for over fifty common building work projects for the home. https://www.planningportal.co.uk/info/200130/Common_projects
This directory lists the approved inspectors that are registered to receive applications through the Planning Portal’s building control application service. https://www.planningportal.co.uk/approved_inspectors_directory
What is a load-bearing wall?
A load-bearing wall is a structural wall, and it is typically a masonry wall, but it could also be a timber stud wall. It is one of the parts of the building that holds the weight of the structural elements which lie above the wall. This could be steel or timber beams, floors, or other walls, and roofs. The load-bearing wall is essential to support the building elements above it, and removal of the lower wall may expose the upper parts to shifting or damage, which over time could cause the structure to collapse.
The weight above is transferred from one level of the house to the next. So, load-bearing walls are typically situated directly over one another on each floor. As all outside walls are load bearing, removing an external load bearing wall for example, always requires structural calculations from a structural engineer.
If there is a previous addition, such as an extension involved, some exterior walls may look like interior walls. In a house that has an unfinished basement or internal spaces, finding the existing structural elements is easier. The supports typically used are steel I-beams, also known as RSJs. Locating the existing steel beams shows where the weight of the house is supported. Any walls that are directly above those beams are likely to be load-bearing.
Knocking down an external load bearing wall – do you need a structural engineer?
If you are removing an external load bearing wall or an internal wall, you should always consult a local structural engineer. If existing architectural plans of the building are not available, a site visit and an inspection by a local structural engineer is typically required. During the site inspection, the engineer will check what is supported by the wall.
Your structural engineer will inspect areas that are accessible only, and some assumptions might need to be made. If your structural engineer is not able to fully confirm what is supported by the wall that is to be removed, the engineer will make assumptions that will need to be verified during construction, by a builder and a Building Control Officer. Alternatively, it is possible to request opening up works.
Based on the architectural plans or findings of the site visit, the engineer will design RSJs that will support the loads which the wall was originally taking. The beam is held up by two other supports, and these might be walls that are capable of taking the additional building loads all the way to the foundations, or new steel columns with new pad footings. Any new beam should normally have at least a 150mm bearing onto the existing walls, but the longer the better.
The beam requires adequate supports on both sides of the opening. If the existing wall beneath the bearings is insufficient to support the new loads, it should be carefully considered before removing an external load bearing wall, as additional strengthening is required. One method of spreading the load and increasing the load-bearing capacity of existing masonry is to use partial brickwork replacement or installing concrete pad stones. The second method involves the installation of masonry or steel columns, and new concrete pad foundations.
It is important to speak to a structural engineer before knocking down an external load bearing wall. The structural engineer will conduct the necessary inspections, prepare calculations, and determine the correct size of the RSJ/beam, or lintel needed. Removing a load-bearing wall is easy with support from a structural engineer.
The structural plan and calculations prepared by your structural engineer should be submitted to your local Building Control. For most small projects, a Building Notice is sufficient. This involves providing basic information about your project and submitting the structural calculations to Building Control. The plan and calculations prepared by us are also sufficient for your builder to proceed with the required structural works. Your Building Control Officer should approve the structural calculations, and inspect any structural work before the installation of the building finishes.
If the wall that is being removed is not load-bearing, a structural inspection is typically required. Following the structural inspection, the structural engineer should prepare a report. This report will be required if a building owner decides to sell or remortgage the property. Mortgage providers require that all structural inspections and reports should be checked and approved by a Chartered Engineer, either by the Institution of Structural Engineers (IStructE) or the Institution of Civil Engineers (ICE). Simplify Structural Engineering is Chartered under the ICE.
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