Increase your home’s potential and value by adding an extension. London & Home Counties Alliance specialise in construction of commercial and residential homes and provide a full life cycle construction service – design and build to meet your requirement. We produce a Gantt chart before starting the project to arrange a work schedule to save as much time as possible. The value of and extension build in London is on average £30,000, as the average house price differs between 2 and 3-bedroom property (£100,000-£200,000).