Guidance for altering or removing roof elements

The removal or alteration to any roof elements could affect how the roof works and cause movement to occur. Movement could cause cracks to occur in the walls and, possibly, the eventual collapse of the roof. When performing work on any roof, care should be taken to ensure the roof will continue to perform effectively and without any movement.

Existing Pitched Roofs

The existing roof structure that forms the loft space has a number of timber elements that make the overall pitch. Each element enables the roof to span across the building and support the tiles/covering on top as well as being able to transfer the loads (weight) created by any wind and snow down to the walls.

Listed below are the typical elements of a pitched roof:

• Ridge Board – This forms the apex of the roof and is where the rafters are fixed to both sides.
• Rafters – These are the timbers that form the main pitch to the roof and support the tiles and battens.
• Purlins – These are long pieces of timbers that are normally seen half way along the rafters and act like beams to reduce the span (unsupported length) of the rafters.
• Struts – These support the purlins.  They are fixed at an angle with one end connected to the purlin and the other on to a load bearing wall or a timber spread across ceiling joists. These are the diagonal timbers seen in the roof.
• Ties – These are timbers which stop the roof from spreading and form an A-frame shape.  They can either be the ceiling joists (as described below) or can be fixed half way up usually above the purlin and are fixed horizontally from front to back. (Common in terraced houses).
• Ceiling Joists – These can act as ties, but mainly support the ceiling below.  Their sizes are usually relatively small and will not be able to take the load of any typical room used in a house.

Existing Flat Roofs

Flat roofs are more simple and generally consist of joists that span the gap between two walls. These are covered by panels which, in turn, are covered in felting or other such coatings as required.

Further information

The following pages give an indication of some of the elements normally required to satisfy the requirements of the Regulations for work on an existing roof:

• Re-roofing
• Rooflights
• Insulation and thermal elements
• Conversion projects

Guidance for fitting a new roof

A new roof will be required to:

• resist weather
• resist the spread of fire from one property to another
• be able to support loads (weights)
• provide resistance to heat loss (insulation)
• be ventilated to protect from condensation (in most cases)
• have adequate drainage

There are generally two types of roof construction used:

• Pitch roof – This is where tiles or slates are used and a void is usually created underneath.
• Flat roof – This usually consists of felting which has a slight fall to allow rain water to drain off.

To enable compliance with the requirements of the Building Regulations to be demonstrated, full details of the new roof will be needed – including materials and their dimensions and performance properties.

Covering

The materials used to cover the roof should be durable and capable of resisting the elements of the weather.  With a pitched roof the type of tile or slate you wish to use will be partly governed by how steep or shallow the slope is.  If the roof is close to a boundary, which is often the case, the roof should also have properties to limit the risk from fire spreading across the boundary.

Ventilation

Not all roofs need to be ventilated. Ventilation is not required to a warm roof system, which is where the insulation is placed above the joists or rafters.   Otherwise ventilation is required and this is known as a ‘cold roof system’.

When ventilating a roof the air should be able to enter at one end and travel through to the other end where it can exit.

Further Information

The following pages give an indication of some of the elements normally required to satisfy the requirements of the Regulations for new roofs:

• Weight (Loading)
• Thermal resistance (Insulation)

When is planning permission for a roof work required?

You do not normally need to apply for planning permission to re-roof your house or to insert roof lights or skylights.

The new rules introduced on 1 October 2008 allow for roof alterations without the need for planning permission, subject to the following limits and conditions:

• Any alteration to project no more than 150 millimetres from the existing roof plane.
• No alteration to be higher than the highest part of the roof.
• Side facing windows to be obscure-glazed; any opening to be 1.7m above the floor.
• The permitted development regime for solar panels has different limits on projections and in relation to protected areas.

Solar panels: for guidance on the planning and building regulations regime for solar panels see Common Projects section.

These permitted development rights apply to houses. If you live in a flat and are considering work on your roof you are advised to contact your LPA for guidance.

Building Regulations

If you want to carry out repairs on or re-cover less than 25 per cent of the area of a pitch or flat roof, you will not normally need to submit a building regulations application. You will need approval, however, if:

1. You carry out structural alterations
2. The performance of the new covering will be significantly different to that of the existing covering in the event of a fire
3. You are replacing/ repairing more than 25 per cent of the roof area, in which case, the roof thermal insulation would normally have to be improved.

There are separate rules for construction of new roofs.