Constructing an extension needs a lot of thought. As well as going through the local authority planning department, obtaining listed buildings consent and building regulations consent you will need to get the landlord's consent if your property is a leasehold dwelling or a freehold house that belongs to a management company.

Considerations will include:

Structural at ground level

• Foundation depth and possibly strengthening of foundations of original structure adjoining.
• How surface drainage will be dealt with.
• Natural light, air exchange and ventilation.
• Overlooking of other dwellings (most local authorities have a rule of 18m clear distance between dwellings).
• Bridging (lintel) support for wall openings to enter into the proposed extension.
• Wall thickness, insulation and SAP ratings (the governments new energy efficiency rules will apply post April 2006 and can require you to upgrade other parts of your property).

Structural at roof level

In addition to the above further considerations include:

• Plumbness of outer walls, a ring beam may be required, or brickwork below the proposed extension that is not plumb may need to be taken down and rebuilt.
• Foundations may need to be strengthened (via underpinning). Underpinning may need to be bridged over drainage runs.
• Means of escape may become an issue over 3rd floor level.
• The exit route to the main fire protected staircase should not be more than 7 metres.

Safety for roof terrace areas

• Protection for any new roof terrace areas, structural security of railing fitments.
• Protection for the roof covering, for example if asphalt, a need to lay asphalt roof tiles to prevent impact damage.
• New roof terrace areas need to be laid to a fall and connections made to rainwater goods.

Considerations for new bathroom/shower rooms/kitchens

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