Understanding what lies below your sunroom extension is vital, and in this guide, we explain orangery and conservatory foundations and what base each ground type and structure requires. What are the building regulations for your sunroom extension and its foundations, and what factors must you consider?
The foundation is one of the most crucial elements of a conservatory, ensuring structural stability and longevity. Choosing the right foundation depends on soil conditions, conservatory size, nearby structures, and intended use, and all the professionals involved will factor in it. Consulting a structural engineer, architect or builder is recommended to ensure stability and compliance with local regulations. We always advise clients to bear in mind that the rules about depth and type of foundation required depend on several factors, which we will detail further on.
Building Regulations Compliance states that a conservatory or sunroom less than 30m², separated from the main house, and having its own heating system is usually exempt from Building Regulations.
However, if your structure is large, has an open-plan design, or is intended for year-round use, compliance with Part A (Structure) and Part C (Site Preparation & Resistance to Contaminants & Moisture) of Building Regulations may be required.
More Planning & RegulationsSome conservatories use the same foundations as a general house extension. In fact, we have built conservatories designed to fit within existing foundations and bases. This ideal sustainable building method is a brilliant way to revitalise your existing living space. However, when grounds are more complicated, conservatories can also be constructed over raft foundations or screw pile foundations.
Although most conservatories require strip or trench foundations, like those used in standard house extensions, specific requirements vary based on ground conditions and design. For instance, a Concrete Raft Foundation may be used if the intended site is weak or has unstable soils. Alternatively, for poor soil conditions or where excavation is difficult, we have also used screw pile foundations.
A raft foundation is a reinforced concrete slab laid to cover the entire footprint of the structure above, spreading the load, lowering the round pressure, and providing a stable base over soft or poor soil conditions or larger extensions – an ideal solution for complex ground issues. Here, you can see a project we undertook for a garden room extension in Yorkshire. The foundations were reasonably complex—the architect conceived a raft foundation with mass fill to ‘bridge’ over a significant concrete obstruction found during excavation.
Screw pile foundations, or helical piles, are deep foundation elements that support structures by transferring loads to stable ground. They consist of a steel shaft with helical plates screwed into the ground. They are ideal for conservatories or sunroom extensions built on soft or moveable soils, uneven ground or near trees with deep roots or areas with heavy vegetation.
Foundation Regulations, depth, and type of foundation required depend on several factors, including soil type, conservatory dimensions, and your local district building regulations. As a guide, in our local region, Yorkshire, the rules of foundation depth are as follows:
The factors that affect the foundation requirements are ground condition, size of the conservatory, nearby environmental factors or structures, and drainage. For instance, a small conservatory may require straightforward strip or shallower trench foundations, whereas, in a forest area, piled foundations are a better choice to minimise root damage. To explain this further, foundations depend on the following factors:
This is a complicated question to answer. The cost will depend on the size of your foundation, its composition, and your existing groundwork. Most builders work on a meterage price, and we estimate that currently, this would be anywhere between £2000 and £5000 per metre square.
As bespoke conservatory, orangery, and sunroom extension manufacturers and installers across Yorkshire, we have overcome many problematic ground types, design obstacles, and installation difficulties and can share our expertise with you. Today, due to changes in conservatory regulation, it has never been more vital to consider every aspect, from roof type and solar gain to the ground beneath. Get in touch to enquire about your project, or find further information below.
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