How to design an extension

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  • With the right materials and smart planning, extending your home can make financial sense

    Maximising your space by extending or converting your property can often take it into a completely new price bracket. It can also be a more cost-effective way of acquiring more space than dispensing funds on stamp duty and moving fees.

    Do bear in mind though, that any work will need to comply with the new Part L building regulations that were introduced by the government to raise the energy efficiency of new structures by at least 40 per cent.

    ‘This means that the proportion of glass in a structure is limited to 25 per cent’ says Susan Venner, of Venner Lucas Architects and Architect Your Home, ‘but you can have more glass if you increase insulation in other areas or choose a high-spec product, for example a Low-E glass or triple glazing.’

    Points to consider when planning an extension:

    – Most conversions need planning permission, but you can add up to 70 cubic metres or 15 per cent of the original space (50 cubic metres or 10 per cent in a terrace) without obtaining permission, so do check.

    – Terraces or semi-detached homes need a party wall agreement.

    – A loft must be at least 2.3m at it’s highest point for conversion and have a permanent access to be classed as anything other than storage.

    – For more on planning and regulations, go to to

    Get more advice on planning an extension, including information on loft conversions and basement conversions.

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