Estimating the cost of your renovation is a fundamental part of the planning process but can be very difficult, as there are always a number of factors so prices are very project-specific.
Factors include the size of your house, the level of your own involvement, location, materials and then the specific list of works that need to be done. Using these factors, one can start to formulate rough build costs.

In order to get started when estimating build costs, there are a number of sources for advice. Firstly, we recommend picking up a copy of Homebuilding and Renovating - they post a table of costs in every issue that estimates the build cost of your project based on location, square metres and the type of builders involved (DIY, subbies, main contractor etc). The table is based on information supplied by the Build Cost Information Service (part of RICS). Of course this is just a rough estimate but it is at least a starting point. For example, using this table for a project in Greater London of around 75-80sqm, the table estimates the following figures:

Main Contractor: £115,000
Builder and subbies:£110,000
Subbies: £105,000

DIY+Subbies: £85,000

Of course, the table does not outline what works are included but it is based on a full refurbishment or average sized extension.
Homebuilding and Renovating also provides two other, more detailed ways to estimate costs. The first is the My Building Project Estimating Service (, a full analysis of your costs based on specific plans. Prices start at £199. There is also an online Build Cost Calculator at which can be used for free advice.

For more detailed information, refer to this Article.

Of course the best way to get an estimate would be to submit the same Schedule of Works to a number of builders or contractors to see the range of prices that professionals would offer - however, this is very difficult to estimate until the Schedule of Works is quite specific. Many clients ask us what we think the cost of their renovation will be - it's one of the first questions asked and obviously of high importance but it puts us in a difficult situation where we can normally only offer a range estimate or show a case study of a previous, similar project. We advise our clients to view as many case studies as possible and to keep in mind a budget when entering this stage, as ultimately it's the Client's budget that defines the Schedule of Works. Unless you are planning on going the DIY route, it's always advisable to work with at least one professional, such as an interior designer, architect or surveyor - your interior designer or architect can guide you through the entire process and make sure you know the costs clearly - often, people overlook costs that would be spotted by professionals and costs rise above the expected. Check with your designer, but often designers pass on their trade discount to their clients and the savings accumulated more than make up for the designer's fees! Not to forget that your project will also be designed and dealt with by professionals who take the stress of budgeting and managing off your shoulders. 

If you are planning a renovation, we suggest you get in touch with us for a site survey and brief discussion on your building requirements so that we can give you a free cost estimate.

Resources: Homebuilding and Renovating