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External Walls

Planning Permission

You do not need to apply for planning permission for repairs, maintenance or minor improvements, such as painting your house.

If you live in a listed building, you will need listed building consent for any significant works whether internal or external.

If you live in a Conservation Area, a National Park, an Area of Outstanding Natural Beauty or the Broads, you will need to apply for planning permission before cladding the outside of your house with stone, artificial stone, pebble dash, render, timber, plastic or tiles.

Outside these areas, cladding may be carried out without having to first apply for planning permission provided the materials are of a similar appearance to those used in the construction of the house.

Building Regulations

If you want to re-render or replace timber cladding to external walls, building regulations may apply depending on the extent of the work.

Where 25 per cent or more of an external wall is re-rendered, re-clad, re-plastered or re-lined internally or where 25 per cent or more of the external leaf of a wall is rebuilt, the regulations would normally apply and the thermal insulation would normally have to be improved.

If you want to insert insulation into a cavity wall the appropriate requirements will be applied to ensure the insulation material is suitable, and that in the case of some foam insulants the risk of formaldehyde gas emission is assessed. Read more about insulation.

Walls can be constructed in various ways by using timber frame structure or masonry structure. 

If using a masonry structure then two forms of construction can be used:

Cavity Wall

This is where there are two skins of masonry, the outer skin can be of brickwork or blockwork and the inner skin is generally of blockwork

The gap between the two skins will vary depending on the type of insulation that is to be used.  To stop the two skins from falling away from each other they should be tied together using wall-ties at appropriate centres.  These ties should also be resistant to corrosion.

The bottom of the cavity should be filled with lean mixed concrete with a slant towards the external skin or have a cavity tray installed that also slants towards the outer skin to ensure any moisture that could get inside the cavity will be directed away from the inner skin.

Solid Wall

This is where there is only one skin of masonry which can consist of brick/blockwork

The high standards of thermal insulation needed in buildings means that it is more difficult to achieve those standards with solid masonry wall construction.  Solid blockwork constructions may meet the requirements if allied with other insulation products and surface finishes.

Existing External Walls in Conversion Projects

Existing walls will need to be checked for their adequacy in terms of:

  • Weight (Loading) and structural stability
  • Weather resistance (including Damp-proofing)
  • Thermal resistance and changes to 'thermal elements'

If they need to be upgraded, this may well involve the addition of a new internal skin - possibly constructed of lightweight studwork. The detail at the foot of the new skin will need careful planning to ensure that damp-proofing arrangements are sound and that any new timbers are protected from damp.

Further Information

The following sections give an indication of some of the elements normally required to satisfy the requirements of the Regulations for external walls:

Decoration and renovation 

Re-decorating the surface of an existing wall would not normally require approval. 

Renovation

External walls are considered to be thermal elements (defined in Regulation 2a of the Building Regulations 2000 (as amended).

It is likely that a renovation of a thermal element will trigger a requirement to upgrade the thermal insulation of that element at the same time.

Fire Protection

Depending on the distance the wall will be from a boundary with an adjacent property, it may also need to provide resistance to fire (to limit the effects of fire spreading from or to adjacent properties).

The area of walls permitted to have reduced or undetermined fire resistance (known as "unprotected areas") - such as openings for windows or doors - will be dependant on how close these elements are to the boundary.

If the wall is also load-bearing, by virtue of supporting a roof or a storey above, it will also need to have fire resistance regardless of its distance from a boundary.

Thermal resistance and changes to 'thermal elements'

The walls having thermal resistance will limit the amount of heat the building will lose from the internal spaces, and gain from the outside environment.  The materials used will determine exactly how compliance is achieved and manufacturers can generally provide some form of guidance for their products.

Cavity Walls - The cavity can be fully filled with insulation or partially filled (consult the manufacturer’s before proceeding). If it is partially filled then an air gap is generally required, the size of which will varying depending on the specific products used for the wall construction and insulation. The insulation should go at least 150mm below the DPC level.

Solid Walls - These walls are generally insulated by placing some form of thermal element on the inside and/or the outside. The thickness of these products will depend on the thickness and type of block used.

Thermal Elements

Making significant changes to thermal elements (walls ,roofs or floors) would normally require Building Regulations approval and require the thermal insulation of the element to be upgraded to a reasonable standard. Walls are defined by Regulation 2(3) of the Building Regulations 2010  as being thermal elements.

The extent to which the work on the element is controlled and the amount of upgrading needed depends on the particular circumstances of the thermal element. Generally, when it is renovated then it should be upgraded, where it is cost effective to do so, to the standard set out in the Approved Document. See section 5 and Appendix A of Approved Document L1B.

The definition in Regulation 2(3) is extracted here for convenience from the Building Regulations 2010 

(3) In these Regulations "thermal element" means a wall, floor or roof (but does not include windows, doors, roof windows or roof-lights) which separates a thermally conditioned part of the building ("the conditioned space") from:

     (a) the external environment (including the ground); or
     (b) in the case of floors and walls, another part of the building which is:
          (i) unconditioned;
          (ii) an extension falling within class7 of Schedule 2; or
          (iii) where this paragraph applies, conditioned to a different temperature,

and includes all parts of the element between the surface bounding the conditioned space and the external environment or other part of the building as the case may be.

(4) Paragraph (3)(b)(iii) only applies to a building which is not a dwelling, where the other part of the building is used for a purpose which is not similar or identical to the purpose for which the conditioned space is used.

Further guidance on this is available in Approved Document L1B covering:

  1. Guidance on thermal elements (Section 5 pages 17-18)
  2. Explanation of when renovation works trigger requirement for upgrading insulation and what additional work may be required.(see Appendix A  and Table A1 pages 21-23)

You should fully consult the Regulations and the Approved Document and, if you are in any doubt, seek advice before commencing work. The definition of a thermal element does not include windows, doors, roof windows or rooflights.

Weather Resistance

In this respect, there are two broad functions a wall needs to perform.

It should resist moisture from the ground and therefore would normally need damp proof courses to do so. It should also be able to adequately resist the penetration of weather from the outside to the inside of the building.

Brickwork generally gives good weather resistance on its own.

However blockwork will normally require rendering to the outside, the thickness will vary depending on the type of block used, but the minimum thickness is about 16mm.

Weight (Loading)

The wall should be adequate to transfer loads, such as from its own weight or the roof it supports, safely to the foundations.

Lintels

If an opening is formed in a wall, the structure above the opening, even if it is relatively small, will need to be supported.  Lintels are normally used to provide such support, in one of two ways:

  1. One lintel (usually made of steel, with insulation integral to it) that supports both the inner and outer leaf of a cavity wall construction.  These usually also serve as a cavity tray which directs moisture from the cavity through the outer skin of the wall construction
  2. Two lintels (made of steel or concrete), one supporting each leaf of a cavity wall construction. Separate thermal insulation and a cavity tray are likely to be required.

With solid walls it is good practice to use a lintel where insulation can be installed to avoid condensation.

All lintels should have a suitable bearing onto the wall at each side of the opening. It is best to consult with the manufacturer or an engineer for the correct size lintel and bearing.

Disclaimer

This is an introductory guide and is not a definitive source of legal information. Read the full disclaimer here.

This guidance relates to the planning regime for England. Policy in Wales may differ. If in doubt contact your Local Planning Authority.