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  • Lccl Construction

Loft Conversion and House Extension

Updated: Mar 17

Everything you need to know about completing a combined loft conversion and house extension project on your home in London, United Kingdom. From how much space you can add, if planning permission is required for your loft conversion and house extension, the costs involved in a loft conversion and house extension and other questions to consider before starting your design and build project.

Loft Conversion and House Extension
Loft Conversion and House Extension

What is a house extension and Loft Conversion combined?

With space at such a premium in most London and home counties homes adding more bedroom and living space is a priority for many families. For some homeowners the best option is to combine a kitchen extension and loft conversion and complete both at the same time. By the end of the project the house is likely to have at least one extra bedroom and bathroom, an additional reception room and much larger kitchen as well as a downstairs wc.

What are the benefits of a house extension?

Whether your aim is to increase the kitchen size, add living space, a utility room or create a ground floor bedroom to meet the needs of your family the advantages of a wraparound extension are numerous:

  • Utilise otherwise unused space to increase the size of the home.

  • Improved saturation of natural light in the downstairs areas through addition of skylights/lanterns

  • Added flexibility to the layout of the home

  • Create space for a large open plan kitchen diner and casual living space where everyone can spend time together

  • Add space to work from home

  • A generously sized utility room can be added to free up space in the kitchen and reduce noise from washing machines/dryers

  • Add a boot room to reduce dirt and clutter cominh into the house

  • Create much needed extra storage space

  • A new patio at the rear or private courtyard can be created at the side

  • Extra 16m2 to 60m2 of additional space

  • Potential for additional space to be added to the first floor too in some circumstances

  • If the garden space is small this is a good solution

  • Extra storage and usable space for everyone in the home to enjoy

What are the benefits of a Loft Conversion?

The benefits of a loft conversion are numerous, whether you are looking to add an extra bedroom and bathroom for a growing family, to create space for family memebers in a multigenerational household or to add an extra room to allow for a home office.

  • Add 40m3 of additional space to a terraced house of 50m3 to a semi-detached or detached home

  • Increase the number of bathrooms in the house with an en-suite or additional bathroom

  • Maximise storage space in the home with eaves storage options

  • Create a dressing room area

  • A nice extended view over the garden

  • Enlarge the capacity of the house by adding at least one extra bedroom

  • Unlock unused potential in your current home with the upheavel and cost of moving house

  • Likely increase in the value of the property by adding an extra bedroom

  • Improved levels of natural light

What are the benefits of combining a house extension and loft conversion?

  • The house will be developed to its full potential

  • Improved saleability and curb appeal

  • Efficiency gains of having the designs and structural calculations done as one project

  • Additional bedroom(s) bathrooms and living space

  • Enlarged social and kitchen space

  • Efficiency and cost savings during the build process

  • Complete your house renovation in one go

  • Better insulation and thermal values

  • Transform the property without having to move

Do I need planning permission for my House Extension and Loft Conversion?

Rules, known as ‘permitted development’ rights, allow you to extend a house and convert the loft to habitable space without needing to apply for planning permission if specific limitations and conditions are met.

For all extensions:

  • Only half the area of land around the "original house"* can be covered by extensions or other buildings.

  • Extensions cannot be higher than the highest part of the existing roof; or higher at the eaves than the existing eaves.

  • Where the extension comes within two metres of the boundary* the height at the eaves cannot exceed three metres.

  • Extension cannot be built forward of the ‘principal elevation’ or, where it fronts a highway, the ‘side elevation’.

  • The work cannot include:

  • verandas, balconies or raised platforms.

  • a microwave antenna (e.g. TV aerial or satellite dish).

  • a chimney, flue or soil and vent pipe.

  • any alteration to the roof of the existing house.

  • On Article 2(3) designated land* the work cannot include cladding of the exterior.

  • The materials used in any exterior work must be of a similar appearance to those on the exterior of the existing house.

For single storey extensions:

  • Single-storey rear extensions cannot extend beyond the rear wall of the original house* by more than four metres if a detached house; or more than three metres for any other house.

  • Where not on Article 2(3) designated land* or a Site of Special Scientific Interest; and subject to ‘prior approval’, the limit for single-storey rear extensions is increased to eight metres if a detached house; or six metres for any other house.

  • This requires that the relevant Local Planning Authority is informed of the proposed work via a prior approval application.

  • Single-storey rear extensions cannot exceed four metres in height.

For Extensions more then one storey:

  • Extensions of more than one storey must not extend beyond the rear wall of the original house* by more than three metres or be within seven metres of any boundary* opposite the rear wall of the house.

  • Roof pitch must match existing house as far as practicable (note that this also applies to any upper storey built on an existing extension).

  • Any upper-floor window located in a ‘side elevation’ must be obscure-glazed; and non-opening (unless the openable part is more than 1.7 metres above the floor).

  • All side extensions of more than one storey will require householder planning permission.

  • On Article 2(3) designated land* all rear extensions of more than one storey will require householder planning permission.

For Loft Conversions

  • To be permitted development any additional roof space created must not exceed these volume allowances: • 40 cubic metres for terraced houses. • 50 cubic metres for detached and semi-detached houses. Bear in mind that any previous roof space additions must be included within this volume allowance. Although you may not have created additional space a previous owner may have done so.

  • An extension beyond the plane of the existing roof slope of the principal elevation that fronts a highway is NOT permitted development.

  • Materials to be similar in appearance to the existing house.

  • No part of the extension to be higher than the highest part of the existing roof.

  • Verandas, balconies or raised platforms are NOT permitted development.

  • Any side-facing windows must be obscure glazed and non-opening unless the parts which can be opened are more than 1.7 metres above the floor of the room in which it is installed. © Planning Portal 2016

  • Roof extensions, apart from hip to gable ones, to be set back, as far as is practicable, at least 20cm from the original eaves.

  • The 20cm distance is measured along the roof plane. The roof enlargement cannot overhang the outer face of the wall of the original house.


Before the loft conversion and kitchen extension
Before the loft conversion and kitchen extension

Before the loft conversion and kitchen extension

If your home is not in a conservation area and meets the above criteria you can most likely carry out a rear extension and loft conversion under your homeowner permitted development rights.

During the kitchen extension
During the kitchen extension

During the kitchen extension

Foundations are dug out and filled with concrete to support the new extension area. The type of foundations will depend on the specifications on the structural drawings and other factors such as the proximity to certian types of trees. The final depth will be confirmed by the Building Control surveyor.

If the layout of the new extension is open plan with the existing house structural alterations will be made to the rear wall as shown in the picture where you can see temporary supports in situ and steel beams ready to be lifted into place and installed.

After the kitchen extension
After the kitchen extension

After the kitchen extension

As you can see here all elements of the kitchen extension including structural aterations, glazing, rendering and a new patio are now complete. The only reamaining feature at the rear is the old roof, which will be removed during the loft conversion.

During the loft conversion
During the loft conversion

During the loft conversion

The old roof is removed and the new loft structure is built, framed, insulated and covered. During the loft conversion process the first and second fix plumbing and electrics are aslo completed, stairs installed, glazing added, plastering and painting completed. This previously disused space will become the master suite of the house, containing a generous bedroom, ensuite bathroom and plenty of built in storage space.

After the loft conversion and kitchen extension
After the loft conversion and kitchen extension

After the loft conversion and kitchen extension

The final result is plenty of extra space on the ground floor and a new master suite, comprising a bedroom and en-suite on the second floor. The liveable space has been transformed and now suits the needs of the owners everyday life. The internal space is light and bright due to the addition of 2 side windows 5 Velux rooflights and 1 large flat roof skylight as well as 5 meters of bifolding doors at the rear. The loft has a spectacular view over the surrounding area.

What is the cost of the loft conversion and house extension?

You can use our "instant quote calculator" and find out the cost in seconds! for both design and build, architecture services or just construction services depend what stage you are in and what you have so far completed.

We have experience of over 15 years in design and construction of loft conversions and home extensions in London and Hertfordshire areas and have worked out a unique calculation formula that you can find out to what your house extension and loft conversion will cost in seconds.

How can Lccl Construction be of help?

Do you require a loft conversion and house extension to add extra space?

Then look no further get in touch with us for a detailed free no obligation quote. We can accommodate a very quick turnaround. Our loft conversions and house extensions come with 10 year guarantee and 12 month workmanship guarantee.

Use our instant quote calculator for a quote about your project whether construction only or design and build.

Use our Free consultation call booking system to schedule a call at the time and date that suits you best.

Telephone: 020 8037 7332



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