You have the vision of a wonderful extension that will make a home perfect for your client's family and their needs, but is it really that simple, consider the following:
1 - If you are planning a new bathroom, wet room, kitchen or utility room have you thought about the services required in that room and where they are located in your original home. Services are generally grouped together it could be costly to join up to services if your new room is not adjacent to the services already in place.
2 - They've always wanted to add a conservatory but will it be useable all year? Consider reducing the amount of glazing in the finished room and the construction of the roof. These will both enable the conservatory to stay warm in the winter and cooler in the warmer months ensuring you can use it all year round and it wont add hugely to your fuel bills in the winter to do so. All designs will still need to be approved by building regulations.
3 - If you are extending to increase the number of bedrooms, have you considered how many bathroom/WC's you may need? For their needs just staying with the original bathroom may be enough but when it comes to resale if a larger family are considering your home they may be expecting more than just the family bathroom. Can you fit in en-suites or an entirely new bathroom too?
4 - Although you don't need planning permission for all extensions, all building work must comply with Building Regulations.
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