Conversions, extensions and renovations

In this article we discuss the current popularity of conversions, extensions and renovations, highlighting the pitfalls and regulations before assessing the advantages of different types of home improvement projects.

A property extension under way.

Lockdown led many homeowners to scrutinise their homes as never before, having been compelled to spend more time in them. Families have perhaps been most affected in terms of living space, often having to find areas suitable for a home office or for schooling children. This has led to a re-evaluation of a home’s purpose, with the consequence that many families are facing the dilemma of moving or extending to create extra space.

Significant numbers of households, having saved money by commuting less and not travelling abroad, have decided on property renovation schemes. The result is a boom in home extensions as householders strive to create more living space in the most effective way.

Extension or conversion options

Loft conversions, side and rear extensions, garage conversions, basement rooms, garden rooms or pods all help create extra space and can add value to a property by helping it reach its full potential. Other possibilities include home renovations such as a new kitchen extensions or a bathroom upgrade to improve functionality and provide just what is needed.

Potential Pitfalls

  • Adding value means that there will be fewer potential buyers if the property outprices the market ceiling price in the surrounding area: this may risk the cost of the property renovation not being recouped in a future sale.
  • Over-extending a house in relation to the size of its plot can have a detrimental effect on the property value; instead of adding to it, the work may compromise a future sale.
  • Light ingress from increased glazing may need mitigation measures to reduce glare and diffuse light. Building Regulations determine the amount of glazing that can be added to an extension which must also meet energy performance standards.
  • A poorly constructed home extension could reduce the value of a property along with the resulting loss of garden space.
  • Be aware of the rising cost and current shortage of construction materials which is causing delays in the supply chain.
  • Ensure that the existing boiler can cope with the extra demands placed on it by a home extension.
  • Check with the local authority to clarify whether a property extension will be liable for Community Infrastructure Levy.
  • Site insurance is required for both the new and existing structure.

Do you need planning permission for a home extension?

Permitted development allows improvement and home extensions without the need to make an application for planning permission if certain criteria are met. The categories of work which do not amount to development are contained in Section 55 (2) of the Town & Country Planning Act 1990.

Permitted development can include loft conversions, property extensions, garage conversions, roof lights, solar panels and new windows, however, there are limits on the height of building work and the distance of new extensions from existing property. In conservation areas and national parks, Permitted Development Rights differ and listed buildings require listed building consent. A change of use application may also be required.

A side extension under construction.

To obtain confirmation that a scheme complies with permitted development rules, an application for a certificate of lawful development can be made to the local planning authority before you can start work. Locally granted planning permission may exist covering the type of development you aim to make, such as a Local Development Order; a Neighbourhoods’ Development Order or a Community Right to Build Order. A site visit by a planning officer may be necessary to clarify just what extension and conversion work is allowed.

Even if a formal planning permission application is not required, other consents may still be necessary such as works to protected trees, listed building consent, environmental permits or licenses. The developer is responsible for ensuring that the necessary permissions are obtained; works carried out without the required consents may result in enforcement action: in all cases it is advisable to check with the local planning authority before site preparation gets under way.

Building Regulations

Even if your home extension can be built according to Permitted Development Rights, the work must obtain Building Regulations approval: this stipulates a minimum standard for design, construction and alterations.

Building Regulations cover matters such as structural integrity, fire safety, energy efficiency, damp proofing, ventilation, electrical work such as rewiring, underpinning, new waste plumbing and other safety checks which will be monitored via site visits during various stages of the building work.


A structural survey may be required, especially on an older building prior to property extension work. Wildlife surveys may also be needed. For example, bat surveys will be required if your development could have an impact on bats, which are legally protected. If trees are present on your development then tree surveys could also be required..


A seamless home extension is often what people aim for, but achieving it requires expertise and flair: it could either take the style of the original building or a contrasting contemporary style can often complement a traditional building.

To ensure that the house extension adds value to the property in relation to its cost, it is important to study comparable properties in the surrounding area and use an experienced team. When building over any existing single storey structure, such as a garage, it is vital to check that it is capable of bearing the extra load: strengthening could be required or it may be cheaper to demolish and rebuild.

A contemporary ground floor property extension.

The Party Wall Act

The Party Wall Act 1996 is relevant as it exists to prevent and resolve disputes relating to party walls, boundary walls and excavations near neighbouring buildings. A party wall exists where owners on either side have a legal interest; a developer must inform adjacent owners about proposed works and they are entitled to object. The Act covers new building work on or at the boundary of two properties; excavations must be within 3m or 6m from the adjoining property depending on their depth.

Class Q Development

This category of development may be relevant to those considering converting redundant farm buildings. Under the Town & Country Planning (General Permitted Development) (England) Order 2015, Schedule 2, Part 3, Class Q allows change of use of a building and land within its curtilage from use as an agricultural building to a dwelling house. It must have been in agricultural use on 20th March 2013; if it was brought into agricultural use after that, a 10 year period must elapse before development under Class Q is allowed.

A 2018 amendment distinguishes between larger and smaller houses; for larger houses the scheme allows for three separate houses with a cumulative floor space not exceeding 465 square metres. For smaller houses there is a maximum of 5 with a cumulative floor space of 500 square metres

Offsite Construction Systems

These may be worth considering as they can save time and money when building a house extension. They can include oak frames, cross-laminated timber, structural insulated panels and timber frames.

Garage Conversions

In line with all extensions, there is currently a huge rise in the number of garage conversions which can add 20% more value to a house and really give it a new lease of life. Garage conversions can often be an effective route to creating additional space: average costs are £6,000, there is often no need to put in new foundations or walls and power may already be in place.

However, foundations may need reinforcing, walls may need repairing and the ceiling height may need altering, all of which will require the services of an experienced team, including an architect or designer. A planning application may be required although most garage conversions will be allowed under permitted development.

Planning permission will be needed if the property is in a conservation area and change of use consent is always required, which needs Building Regulations approval. It is also important to check the property deeds to ensure that there is no requirement for parking to remain as part of the property.

Loft conversions

One of the main advantages of a loft conversion is that they avoid building over valuable garden space and, in many cases, require less labour: walls and a roof are in place therefore often minimal structural change is required. Loft conversions also offer the opportunity to incorporate increased insulation into the roof, making the house more energy-efficient.

The work is also less weather-dependent than external extensions, less disruptive, faster and can be cheaper. According to a report by Nationwide, adding a loft conversion to create an additional bedroom and bathroom can add 21% to the value of a property.

Basement Extensions and Cellars

The main reasons for deciding to dig underground are to retain garden space or because possibilities for above ground expansion are exhausted. Planning permission will be needed – the local authority will have a specific policy on underground development – and it is useful to be able to prove precedent if neighbours have successfully built basements.

The local water table is a crucial factor; a high water table can increase costs: to find out, consult the Environment Agency’s flood map. Access to the site for the various stages of building work also needs consideration. An experienced team will be needed, including a specialist architect and a structural engineer, to carry out various reports to the highest standards.

Kitchen and Bathroom Extensions

The full potential of a house can often be realised by an outstanding kitchen extension. It is advisable to confirm the positioning of the units, cooker and white goods early on in any scheme to allow planning for electrics, plumbing and ventilation. Plumbing schemes for bathrooms should also be decided on at an early stage.

Converted Churches and Barns

While churches will probably be listed and require specific planning permission, they can make exciting spaces to live in if converted with sensitivity. The open space available in churches and barns can adapt successfully to an open plan layout but as a bespoke approach is often needed, projects can be costly and the highest standards must be maintained: an experienced team and the services of a Master Builder may be needed. A solicitor may also be required to advise on rights of access and restrictive covenants: deeds must be carefully looked at.

It must be noted that external changes are generally not allowed and relatives must have the right of access to visit remains of the deceased. The architect should work with the existing structure to create a workable scheme, retaining the building’s essential character where possible. While compromises are inevitable, energy efficiency is key to satisfying Building Regulations.

Surveys may be required

To obtain planning permission for some conversions and extensions, specific reports may be needed such as protected species, ecology or tree surveys. Arbtech have expert consultants covering the entire UK who can provide a speedy, efficient service proven to help clients gain planning consent.


Town & Country Planning Act. 1990. [Online]. Available here. (Accessed 12th August 2021)

Gov.UK Guidelines. 2021.When is permission required? [Online]. Available here. (Accessed 12th August 2012)

Home Building & Renovating. 2021. [Online]. Available here. (Accessed 11th August 2021)

Ideal Home. 2021. Will a kitchen extension add value? [Online]. Available here. (Accessed 11th August 2021)

Our Property. 2021. Buying a church conversion. [Online]. Available here. (Accessed 11th August 2021)

Grand Designs Magazine. 2018. Converting a unique building into a stylish home. [Online]. Available here. (Accessed 11th August 2021)

Finance Digest. 2021. How your home can benefit from a loft conversion. [Online]. Available here. (Accessed 16th August 2021)

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