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)

Guidance for converting your loft space

This section provides guidance for making alterations to the loft space of an existing house which is no more than two storeys high. Requirements for alterations to an apartment or other dwellings like maisonettes, or houses over three storeys, will be similar but may be more extensive and possibly extend to other parts of the building.

The regulations will be applied to ensure, for example:

• the structural strength of the new floor is sufficient
• the stability of the structure (including the existing roof) is not endangered
• safe escape from fire
• safely designed stairs to the new floor
• reasonable sound insulation between the conversion and the rooms below.

You may wish to make these alterations to enhance the storage facilities available or to increase the living space of the home.  If you plan to make the loft space more accessible or more habitable by, for example, installing a stair to it and improving it by boarding it out and lining the walls / rafters etc, more extensive work is likely to be required and the Building Regulations are likely to apply.

It is recommended that you contact Building Control to discuss your proposal and for further advice.

Boarding-out for storage

In most homes, the existing timber joists that form the “floor” of the loft space ( i.e. the ceiling of the rooms below) will not have been designed to support a significant weight (known as “load”). The joists tie the pitched members of the roof together to prevent them spreading and support the ceiling lining of the rooms below.

An excessive additional load, for example from storage, it may mean that the joists are loaded beyond their design capacity. If you decide to lay flooring boards over the existing joists in the loft space, then this may require a Building Regulations Application to Building Control. Your local Building Control body will be able to advise you on this issue.

Creating a liveable space

If you decide to create a liveable space in an existing loft space of a home it is likely to require a range of alterations. Many of these could have an adverse impact on the building and its occupants if they are not properly thought out, planned and undertaken in accordance with the requirements of the legislation.

Further Information

The following pages give an indication of some of the elements normally required to satisfy the requirements of the Regulations when converting a loft:

• Existing walls & foundations
• New Dormer
• New internal elements
• Fire safety
• Stairs

The following common work sections give an indication of several other elements normally required to satisfy the requirements of the Regulations when converting a loft:

• Drainage
• Electrics
• External Walls
• Kitchens and Bathrooms
• Internal Walls
• Roof
• Windows and doors

You must also find out whether work you intend to carry out falls within The Party Wall etc. Act 1996.