At Stevens Martin Partnership we regard cost planning as the single most important service we provide. This is because, more often than not, a lack of accurate cost planning is what leads to budgetary problems when building.
Ideally the process of cost planning should begin when the first set of architectural drawings is produced and prior to any application for planning permission. Otherwise it may happen that planning permission is granted for a building that can't be completed within budget.
Unlike a budget estimate, a cost plan is based on a combination of actual design drawings and more detailed information regarding the final specification of the building, and is therefore much more accurate. It's also an excellent way to determine whether specification changes need to be made to a design - in order to bring it in line with a budget - before planning permission is applied for.