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Loft Conversions

Loft Conversions:  A basic guide

Since the recent changes to part B there has been a fundamental change to means of escape requirements to many loft conversions. This guide gives basic information to try to point you in the right direction when planning a loft conversion.

Loft conversions are often problematical as it is sometimes difficult to arrange suitable access, while providing sufficient usable space, together with adequate levels of insulation & structural integrity. In this guide the various relevant parts of the Building Regulations will be examined in turn. The information provided is intended to act as a pointer to the requirements and reference should be made to the Approved Documents for full details.

However the first decision to make is whether to submit a Full Plans application or a Building Notice. If the work is relatively simple & the contractor is familiar with the requirements in the Building Regulations, a Building Notice may be all that is needed. However, this is a high risk strategy, and more complex jobs may be better dealt with by a Full Plans submission.

The fees for loft conversions will be based on the estimated cost of the works. To ensure consistency, this must be based on the estimate that a builder would charge, and not what it may cost the applicant operating on a DIY basis. Where the extent of the works means that the major part of the roof is new, the fees will be based on an extension of floor area created.

Part A (Structure)

The alterations must ensure that the structure can take the loads imposed by the loft conversion. At its simplest this may only involve minor alterations to the existing roof. However new floor joists will be required in nearly all cases &, in many others, additional beams may be needed. This may require some structural design work and the provision of calculations to justify the design. In some cases the existing roof will be made of trussed rafters, which will further complicate the structural design.

Part B (Fire Safety)

If the work is to convert the roof space of an existing bungalow, the means of escape is relatively straightforward, relying on making sure that the floor to the new rooms is adequately fire resistant & that escape windows are provided to new habitable rooms & bedrooms.

Where the loft conversion is to create a three storey house it is no longer acceptable to rely on escape windows to the new rooms. Three storey properties require a protected escape route with fire doors (FD20) surrounding the stairs, landings & hall to all habitable rooms. These doors do not have to be self-closing. Open plan layouts will not be looked on favourably, although the option of seeking a fire risk design is open; this would necessitate specialist design input.

In some cases it is proposed to alter the loft space above a flat to create new rooms; this may be more problematical regarding means of escape and will probably require careful planning, possibly requiring alterations to improve the means of escape in the common areas of the block of flats concerned.

In all cases there will need to be adequate fire resistance to the floors and mains operated, interlinked smoke detection provided.

Part E (Sound Insulation)

New floors should have sound resistant qualities; this will require ceiling & flooring of sufficient mass, and the insertion of sound-deadening quilt. Existing separating walls to adjoining properties will need to be upgraded to provide a reasonable level of sound insulation between dwellings.

Part F (Ventilation)

The provision of cross ventilation to the roof void can create problems as both high & low level vents will be needed. In addition effective cross ventilation requires a suitable, clear vent path above the level of any insulation. This should remain unobstructed, and may require extra vents where obstructions, such as roof lights, exist. One easy solution to this is found where the alterations also involve re-roofing, where the provision of a breathable under-felt will remove the need for vents.

Part H (Drainage)

Any new drainage must be able to discharge to the existing foul drainage system. Existing vent pipes may need to be extended to a height sufficiently clear of new windows. The provision of air admittance valves may be acceptable if adequate ventilation is provided elsewhere.

Part K (Stairs)

In nearly all cases a staircase that meets the full criteria of Part K will be required. This will need adequate headroom, although the full 2m requirement may be reduced in certain circumstances

Part L (Conservation of Fuel & Power)

The external fabric to the loft conversion will need to be insulated to meet the U values required. In some cases this can create conflict with the need to cross ventilate the roof void, and in most cases will require adding depth to the sloping section of any ceiling to accommodate the insulation. Insulation may be in the form of rigid boarding, or may be one of the new, hi-tech, multi-layer barrier materials. In all cases insulating materials should be installed in accordance with the manufacturer's requirements. It is worth noting that materials that seem similar may require different thicknesses to achieve the required U value.

Loft conversions can often be undertaken without Planning permission, but the Local Planning Authority, whether the New Forest District Council or the National Park Authority, should be consulted to ensure if this is the case.

Updated: 23 Oct 2014
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