costing a project in the early stages.
The general rule of thumb used by builders is to calculate the floor area of the proposed project in square metres, and base the project cost on between £1000-£1200/sqm for straightforward new build houses on a flat site. If the design is more innovative or if you have more expensive tastes this figure can be higher still. Site conditions can also affect the costs, such as sloping sites and ground conditions.
Extensions and renovation projects become more difficult to cost as they are generally more expensive given the nature of existing buildings (increased risk) and issues regarding site access. For all projects a good measured survey at the outset is essential, as correct and accurate information will inform you and the architect when making the fundamental design decisions. Base your initial calculations between £1200 and £1500/square meter to get a rough idea of what you might be paying. Remember at the early stage of the project this is a rough estimate. The more complex the design the more expensive it will be.
Choice of fittings will also push up the price of any project. You only need to look at the huge variation in cost of kitchens to demonstrate this.
Don't forget professional fees and fees payable to the Local Authority for planning and Building Regulations , which can be overlooked. Of course you can do much of the work yourself to reduce the costs; self-builders sometimes look to project manage the project themselves. It all depends in the level of risk you want to take on board.
If you are looking to project manage your build, it is always a good idea to get a QS to provide a build cost, based on a priced bill of quantities. This is an inexpensive way to establish a benchmark to test your builder's quotations against, using standard measurement etc.....