How to Build an Extension & Basement

Sketch your ideas for your extension and basement. You do not need to be exact; you just need to get your ideas down onto paper and think through the aesthetics. Obtain the original blueprints for your house, either from your own files or by asking the original builder for a copy. Most will keep their blueprints on file and provide a copy for a nominal fee.

Measure the land that you wish to build the extension and basement on. You have to hire a professional land surveyor due to the basement. You need to know how much weight the ground can support, and if there are rock formations close to the surface. You also need to know how the land undulates, and if you need to grade the surface to properly support the extension and basement.

Call your local power, water, cable and gas companies to ask them to mark their pipes running through your property. You need to know where all the pipes are because of the basement dig, and because some of the construction equipment is heavy enough to crush underground pipes. If the pipes are in the way, you can still get the extension and basement built, but it will be more expensive as you will have to re-route the pipes.

Obtain bids on the construction project from local contractors. Because of the large size of this project, there may only be a limited selection of contractors, especially if you live outside of large metropolitan areas. Provide each of the contractors with copies of your blueprints, sketches, surveyor's reports, and the location of the underground infrastructure. Each contractor will want to perform their own inspection of the building and the land. Schedule separate times for each. Compare the bid prices that the contractors give you, but keep in mind you get what you pay for. Going with the cheapest option when it comes to a home project is not a good idea.