Loft Conversion Planning Permission Guidelines

Loft conversion construction plans

Planning permission, listed building & conservation area consents

Planning permission for a loft conversion is not needed if:

  • The roof space created will not exceed 40 cubic metres for terraced houses and 50 cubic metres for detached and semi-detached houses.
  • No extension beyond the plane of the existing roof slope of the principal elevation that fronts a highway is proposed.
  • 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.
  • No Verandas, balconies or raised platforms are proposed.
  • Any proposed 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.
  • The roof extensions (apart from hip to gable) is to be set back by minimum 20cms from the eaves.

We recommend that you check with the Local Council before you undertake any construction, or call us for free advice.

In listed building/conservation area circumstances, consents may be required for your loft conversion and no works should be commenced until approval has been given by the planning department.


Obtaining building regulations approval

The building owner must make a building regulations application & pay a fee for the proposed works. KPD Construction will deal with this on the owner’s behalf. All work must comply with the Building Regulations and the technical design and constructional requirements of the current Approved Documents A to P and Regulation – 7 Materials and Workmanship.

KPD Construction will liaise with your Local Authority and meet the requirements of the LA Building Control/Certifying Body, giving required notices of stages of works as required by the Building Regulations so that the Local Authority can inspect the work as it progresses on site. When the project is satisfactorily completed a Building Regulations Completion Certificate will be issued showing that the project has been independently inspected and that it complied with the Building Regulations.


The Party Wall Act of 1996

In terraced or semi-detached houses, the conversion is usually affected by the Party Wall Act. In such a case, you may be required to give your neighbour the required notice under the Party Wall Act. KPD Construction will deal with this on the owner’s behalf

Two months notice in writing is to be given to the adjoining owner(s) for the following works to an existing Party Wall:

  • Support of beam
  • Insert DPC through wall
  • Raise wall or cut off projections
  • Demolition and rebuilding
  • Underpinning
  • Insert lead flashings

Excavations within 3 meters of an existing structure where the new foundations will go deeper than adjoining foundations, or within 6 meters of an existing structure where the new foundations are within a 45-degree line of the adjoining foundations.

Making an assessment of just how feasible a loft conversion is

It is of critical importance to make an assessment of how feasible would converting a loft be. The procedure would be quite simple and would require inspection of the existing roof space and the dwelling as a whole by an experienced trader.

In general, the following would be considered:
The existing roof structure. Its size and form- The existing roof structure, its size and design and construction features is a major item to be considered for suitability. Timber pitched roofs construction with gable ends walls are in general easier for conversion. The conversion will require a new structural beam being introduced at ridge level.

In hipped roofs scenarios, the structural designs may be more demanding and structural calculations will be needed by a qualified Structural Engineer.

Existing timber structure

Existing timber work should be in a good condition and should not show any sign of deterioration or biological attach such as insect or fungal attack. Careful inspection would be needed and in case of any defects found, consideration will need to be given in the design for the conversion. Again, you will need to ensure that a suitably qualified and experienced specialist.

Headroom availability

This is critical to any conversion and is measured vertically from the finish level to the underside of the proposed horizontal or sloping roof. A clear headroom of 2.0m minimum would be required in order for the conversion to be compliant with building regulations. The same requirement applies to the stairs. Hence, in cases where there is not enough headroom, lowering the existing floor level can be considered for feasibility. Greater ceiling heights are better and would make the conversion feel more spacious.


To the underside of the new storey floor should achieve 30 minutes of fire resistance. Normally 13mm plasterboard & skim or sound lath and plaster in older houses will achieve this, otherwise additional upgrading will be required.

Existing roof coverings

As for the timber, any covering should be in good condition and weather tight. In not the case, consideration is to be given for reconstruction which needs to ensure that new detailing are compliant with building regulations and any replacement are to match existing as required by planning. There is a variety of products which can be used and it is to be ensured that in all cases, the manufacturer’s instructions are followed.

Means of escape

Any two-storey conversion will be deemed as a three-storey house and this will imply additional protection for fire safety. Hence the stairs from the new loft to the final exit at ground floor level will require fire-resistant construction with all doors to habitable rooms changed to fire doors such as to form a fireproof corridor system. Usually, this should achieve 30 minutes of fire resistance. In actual construction, use of 13mm plasterboard and skimming or the use of sound lath and plaster will enable compliance with the 30 minutes fire resistance requirement.

Converting an existing loft space

Converting an existing loft space can be an easy and cost-effective way of increasing living accommodation in most houses. This guide provides useful guidance on how some of the technical design and construction requirements of the Building Regulations can be achieved where the loft space of an existing one or two storey dwelling is being converted into habitable accommodation to form an additional storey to the dwelling.

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Everything you need to know is right here!

Construction work can be complex and a little confusing for those outside of the industry. We want our customers to have clarity when it comes to understanding the different aspects of construction work we carry out and what is important to consider when planning on having work done on your home. That’s why we have created a catalogue of useful articles with the help of industry experts as well as our own team – to share our knowledge and keep our customers informed, aware and confident in their decisions.

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