Planning permission is not normally required to turn two properties into one by knocking through a party wall provided the changes are internal and do not impact the external appearance of the property.

You should check with your local planning authority that they agree, and there are not any previous planning changes or conditions which may have an impact.

Additional permissions may be required depending on the building’s history and their location. If the building is listed, an application for listed building consent will be required before any major changes are made to the dwellings.

The work will have to comply with building regulations, the focus will be on structural work and safety.

‍Read more about how building regulations apply to internal walls.

If you do not seek planning permission, build without it when it applies, or do not meet specified conditions of a planning permission, this is known as a planning breach.

Your local planning authority can serve an enforcement notice on you when they consider you have broken planning rules. You may be given the opportunity to apply retrospectively, or be required to remove a building or structure, or alter it to make it acceptable.

Read about your responsibilities.

Adding a porch canopy is classed as permitted development provided it meets the limits and conditions set out in legislation. Where this is the case, no application for planning permission is required.

Porches must meet the following limits:

• the ground floor area (measured externally) would not exceed three square metres.
• no part would be more than three metres aboveground level (height needs to be measured in the same way as for a house extension).
• no part of the porch would be within two metres of any boundary of the dwellinghouse and the highway.

Read our mini guide for additional information on installing a porch.

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Inserting new windows which look similar to those previously used in the house will often not require planning permission. Some rules apply to new additions, for example if they are on an upper-floor side elevation they must be obscure glazed and non-opening or more than 1.7 metres above the floor.

Installing a new bay window on the front elevation would require planning permission as it is classed as a forward extension.

If you live in a listed building or conservation area you should contact your local planning authority.

 Any new openings will have to comply with building regulations, this may impact thermal heat loss, structure, ventilation and fire safety.

You can use a member of a competent person scheme to complete any work, this will ensure that the work is completed in-line with regulations.

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Foundations are required to carry and distribute the load of the building safely. Therefore, all buildings should have adequate foundations. The factors that need to be considered when designing a foundation are:

• Type of soil
• Adjacent structures
• Trees
• Drains and sewers
• Size and construction of the new building
• Ground condition
• Landfill sites

It is advisable to contact a structural engineer or speak to a building control body about plans for new foundations. 

Read more about foundations for extensions.