At a time when many home owners choose to improve rather than move, a simple loft conversion offers the ideal solution to realise the full potential of your home.


Loft conversions are a great way to increase the useable space within your home without compromising your outdoor space and also provide a cost effective solution to add value to your property.

“Do you love your home and the area in which you live? Would you love that extra bedroom without the cost of the next rung on the property ladder?”
If so, a loft conversion could provide the cost effective solution.

Depending on the original roof structure and planning constraints, a loft conversion is a great way to gain extra space in your home and can be applied to almost all houses. This article sets out to help you to understand your property and realise the design solutions available to help you achieve your dream home.


How to check if your loft can be converted

Not all lofts are suitable for conversion and so it is worthwhile checking the following before getting started:

  • Head height
  • Pitch
  • Type of structure
  • Existing water tanks/ chimneys

Ideally the existing height from the top of the bottom chord to the underside of the ridge timber should be a minimum of 2.2m. The steeper the pitch angle, the higher the central height is likely to be.

Where a water tank is in the original loft space, the heating system will need to be replaced with a sealed system. Depending on the size of the house and number of bathrooms/ en-suites, this may be either an unvented hot water cylinder system or combi boiler system. Both require adequate storage areas, and so this must be considered when opting for a loft conversion.


Types of Roof

There are a number of styles and age of home across the UK. The following are the most commonly found roof types:

Types of roof structure

Roof structures are typically ‘traditional framed’ or ‘pre-fabricated truss section’ types, which varies depending on the age of the home (most commonly either pre or post 1965). The original roof structure can impact the level of conversion work required.


Traditional Truss

Traditional frame types are generally found in houses built pre-1965. The rafters, ceiling joists and supporting timbers are cut and assembled on site. This is the most suitable type of roof for conversion as the space can be easily and relatively inexpensively opened up by strengthening the rafters and adding supports (purlins or steels) as specified by a structural engineer/ truss designer.

Beams are often required to provide support to the new floor structure. Non-complex conversions can be achieved as self-build projects provided that Conversion Insurance is obtained (see Conversion Insurance notes).

Pre-fabricated Truss

Pre-fabricated truss sections are a popular roofing construction method used today and are commonly found in homes constructed after 1965. The timbers tend to be thinner and require additional braced diagonal timbers. As pre-fabricated trusses do not need additional load bearing support beneath them, this type of roof requires a greater added structural input when re-designing for a loft conversion.

This will normally involve the addition of steel beams between loadbearing walls for new floor joists/ rafter section to be supported on, together with a steel beam at the ridge. This then allows the bracing sections of the trusses to be cut out to create a clear floor area. This type of conversion requires specialist input from structural engineers/ truss manufacturers and appropriately qualified installers.

Types of Conversion

Room in Roof Loft Conversion

A roof light conversion is converting your loft without changing its original shape. This is a good solution for higher roofs where head space isn’t a problem. The work usually entails the following:
  • Reinforcement of the floor
  • Addition of skylights
  • Added insulation
  • Staircase to the loft
  • Electrics, lighting and heating
  • Fire safety measures (in compliance with AD Part B) such as fire doors and smoke alarms
This is a popular choice for many period properties especially those situated in conservation areas. The discreet design and low impact on external alterations are a cost-effective method for adding space to a property.

Dormer Loft Extension

The level of work required is as per the items listed for a roof light conversion, but with the inclusion of dormer windows. The advantage of this type of conversion is that it increases the useable floor space and can be used to add head height. Dormer loft conversions are versatile in that they can be built on variously different styles of homes, such as on terraced houses, end of terrace, semi-detached and detached houses. Additionally, dormer loft conversions allow greater flexibility in locating the access stair, with a popular location being directly above the existing stair. There are many choices of dormer loft conversion including:

Flat Roof Dormer

Flat roof dormers offer a great solution to adding space to lofts and are a popular choice to Victorian terraces, where the flat roof can be constructed in an ‘L shape’ formation to the rear of the house.

Side Dormer to Hip

This type of dormer offers an attractive alternative to a hip to gable loft conversion, particularly if the latter is not acceptable through planning.

Lead Clad Dormer on Front Elevations

Ideal for houses within conservation areas and where planning will only grant up to 1.8m in construction of a dormer. This option will still allow for a new staircase and sizeable room.

Hip to Gable

A hip to gable loft conversion is suitable for semi-detached, detached or end terraced housing. Generally hipped roofs have a very restricted internal area due to three/ four sides of the roof sloping inwards. A hip to gable loft conversion allows for a simple staircase fitting above the existing (when located on the gable end). A side dormer could provide an alternative solution where a hip to gable conversion will not be accepted by planning. A hip to gable conversion can allow for a larger rear dormer to be constructed, maximising your interior space.


A mansard loft conversion requires the most work to the property due to the large scale of the structural alterations needed and will generally require planning permission. This type of loft conversion generates the greatest increase in internal floor area. A introduces a flat roof area and sloping back of 72 degrees (planning authorities view 72 degrees as a roof rather than a wall), allowing the build to incorporate as much additional space as possible. Windows are included as small dormer windows and the gable walls are raised in matching brickwork as parapet walls (terraced formation).

Gable to Gable

This conversion design is suitable for terraced houses. Here the rear roof is re-built, and the gable walls are built up to raise the pitch, so it is almost level with the ceiling hence creating some significant space.

Alternative Solutions for Roofs with a Low Head Height

Option 1 – Raise the roof/ replace
This option is best applied to roofs with a shallow pitch, as using any of the other conversion designs can be costly with less benefit.
This would involve removing part or all of the existing roof and rebuilding it to give the required height and structure.
Roof replacement is the most expensive conversion option as it involves the removal and rebuild of the existing roof which requires a specialist truss design. It also requires planning approval. Methods include either construction on site using pre-fabricate attic trusses craned into place or by installing a pre-fabricated modular system.

Attic Truss

Modular Roof

Living without a roof for over a month can be inconvenient, modular solutions are craned into place and can offer a water tight roof in a couple of days. Modular systems offer convenience where time is an issue.
Option 2 – Lower the ceiling in the room below
Older properties tend to have higher ceilings (approximately 3m or more) so if the roof space height is limited, lowering the ceiling could be an option provided that a minimum of 2.4m is retained. A suitable tie between the roof structure and the formed dwarf wall will be required to prevent the roof from spreading. The new joists will need to be hung from wall plates bolted to the walls.



Many loft conversions will fall under Permitted Development Rights (where not removed under Article 4 direction in sensitive areas).
Permitted Development criteria includes:
  • Permitted – Loft extensions without enlargement of the roof
  • Permitted – Roof windows projecting less than 10mm
  • Permitted – Dormer windows to the rear and side elevations are permitted (glazing and height restrictions apply)
  • Permitted – All window opening parts should be no lower than 1.7m from floor level
  • Permitted – Overall increase in volume can be up to 50 cubic metres (40m3 on terraced houses).
  • Hipped roofs can be altered to gable roofs provided the Local Authority have fully adopted the Hip to Gable Permitted development rights.
  • Not permitted – Loft extensions on designated land
  • Not permitted – Rooflines fronting the highway; no extensions are permitted beyond the plane of your existing roof slope.
  • Not permitted – Verandas, balconies or raised platforms
  • Not permitted – Roof enlargement cannot overhang the outer face of the wall of the original home.
Where a loft conversion falls within Permitted Development criteria and mitigates the need for planning permission, a certificate of Lawful Development should be obtained from your Local Planning Authority and should be provided to your purchaser’s solicitors when selling the property. Where the design does not fit within Permitted Development criteria, a Householder application will need to be submitted to your Local Planning Authority.

Building Regulations

Loft conversions need Building Regulations approval regardless of whether they need planning permission). Opting for Full Plans approval takes much of the risk out of the construction work and means that the builder will be able to provide you with a fixed quotation, rather than a vague estimate. Your Building Control officer will inspect the work at various stages. On the final inspection, they should issue you with the completion certificate. A copy will need to be provided to your purchaser’s solicitor should you choose to sell the property in the future.

Party Wall Act 1996

If your home is semi-detached or terraced, then your neighbours will need to be notified via the Party Wall Act requirements. The Party Wall Act covers the following:
  • Various work that is going to be carried out directly to an existing party wall or structure
  • New building work at or astride the boundary line between properties
  • Excavation within 3m (where the work will go deeper than the neighbour’s foundations) or 6m (where the work will cut a line drawn downwards at 45 deg from the bottom of the neighbour’s foundations).
Where works that fall within notifiable criteria of the Party Wall Act apply, all adjoining owners must be formally notified.
Although the Act contains no enforcement procedures for failure to serve a notice, if you start work without having first given notice, adjoining owners may seek to stop your work through a court injunction or seek other legal redress.
An adjoining owner cannot stop someone from exercising the rights given to them by the Act, but they may be able to influence how and at what times the work is done.
The building owner must provide temporary protection for adjacent buildings and property where necessary. The building owner is also responsible for making good any damage caused by the works or must make payment in lieu of making good if the adjoining owner requests it.
Notice should be issued at least two months before the planned starting date for the work to the party wall and one month for excavations and is valid for one year.
Examples of notifiable works under the Party Wall Act are works that could impact the structural strength and support functions of the party wall as a whole, or cause damage to the adjoining owner’s side of the wall, such as:
  • Cutting into a wall to take the bearing end of a beam (for example for a loft conversion), or to insert a damp proof course all the way through the wall)
  • To raise the height of the wall and/ or increase the thickness of the party wall and, if necessary, cut off any projections which prevent you from doing so.
  • To demolish and rebuild the party wall
  • To underpin the whole thickness of a party wall
  • To protect two adjoining walls by putting a flashing from the higher over lower, even where this requires cutting into an adjoining owners independent building
Further details can be found within the Department for Communities and Local Government Party Wall Act 1996 – Explanatory Booklet.

Conversion Insurance

Should you choose to opt for conversion works then you will need to obtain conversion insurance to cover the new works and existing structure. Most home insurers will exclude loss or damage whilst the property is undergoing alterations and so conversion insurance is essential. Loft conversion projects can be complicated and often include liability assumed under the Party Wall Act 1996.
Conversion insurance needs to be in place from the moment you plan to start works on the property and should continue until the point of use.