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UK Building Regulations - Information

Loft Conversions, Dormer Extensions, Regulations and Permissions

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Building Regulations - Information

Loft Conversions

If you are thinking of converting unused attic space to extend your home you may to know that building work needs to be constructed to reasonable health and safety standards.

Building controls ensure that alterations are carried out correctly so they do not cause problems at a later stage. For example, there could be problems in selling your home if changes are not noted in your house plans or a structural problem results from use of inadequate materials.

As professional builders, we must consider:

  1. Structural Stability
  2. Fire Resistance
  3. Access and Means of Escape
  4. Weather Resistance and Energy Conservation
  5. Ventilation

1. Structural Stability

If the space is for use other than light storage then a new floor will have to be provided.

The existing ceiling joists are not designed for heavy loads.

Any alterations to the roof structure such as skylights or dormers require careful consideration so they do not adversely affect the overall stability of your roof. This includes assessing load baring walls - their construction and foundations.

Any structural members, e.g. beams, beam bearings, posts, trimmers and connection details must be justified by calculations.

2. Fire Resistance

UK Building regulations require loft floors and certain walls and doors to resist fire for a specified period (usually half an hour).

The correct form of construction will protect occupants in the conversion for this period.

Staircases need to be enclosed by construction (doors and walls or partitions) with 30 minutes fire resistance, or, existing doors retained, if not glazed and self-closing.

En Suite bathroom or toilet doors need not be fire resistant. The condition of existing doors and doorframes are assessed.

The installation is to comply with BS5446: Part 1: 1990 or BS5939: Part 6: 1995 with regards mains powered smoke detectors.

The dormer roofs need to be capable of resisting external fire spread for at least 30 minutes.

3. Access and Means of Escape

Access to the converted loft is via a flight of stairs and you need to consider the type of stair you require.

Traditional strait stairs will give safe and easy access, however other types are available such as double and triple kite wind and others will tend to gain approval where space is restricted.

Stairs also provide a safe escape route for occupants in the event of a fire.

For two storey houses. Building Regulations give specific advice on the loft conversions in these situations.

Particularly, the route must discharge to an external door - the staircase must discharge close to a door leading to an external safe place and not in a room.

Escape windows such as the VELUX® escape/access skylights are no longer required and optional - they are designed to be large enough to escape through, and positioned for easy rescue by ladder.

4. Weather Resistance and Energy Conservation

The loft walls and roof must keep out the elements and retain heat.

The materials we use in construction are designed to reduce heat loss. This will conserve energy and cut your fuel bills.

External loft walls are constructed to achieve a U-value of not more than 0.35W/m2oK, and roof areas to achieve a U-value of not more than 0.30W/m2oK.

5. Ventilation

Building regulations provide guidance on ventilation so a health living environment is created.

Ventilation provides clean air to the living environment and vents moist or stale air, which would cause condensation.

Ventilation is also required under the roof tiles, again to prevent condensation that would not be seen or detected before it caused serious problems.

Ridge vents to a continuous 5mm gap and eaves vents to a continuous 25mm gap are built in front and rear - unless a vapour permeable sarking layer (breather felt) is used.

Dormer are built with a warm deck roof, ridge vents to a continuous 25mm gap.

Ridge vents are positioned to ventilate the roof space above ceiling level.

To reduce risk of condensation, a vapour check layer is added at ceiling level to restrict water vapour from rooms into the roof space.

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