Although the cost of building an extension is made up

By this stage you will hopefully have a good idea of how much your house extension will be, what parts will cost the most, and where you can change your choices to control the cost if you need. Major home updates, like building an addition or remodeling a room, are some of the most expensive projects you can complete. Although the cost of building an extension is made up of a large number of elements, you can think of it in 4 main categories. The cost of a typical high spec glass extension is around £2,500 per m². So these are parts of the design where you can start to refine your cost estimate as necessary. To get beyond the ballpark figures we can calculate the actual construction cost of an extension in more detail. The structural engineer inspects the foundation, infrastructure, curtain wall, insulation and building envelope. Through careful inspection and comparison to the approved building plans, the engineer can ensure that the actual building meets the drawings provided and that any necessary corrections are made. For example on sites where access is difficult or there are unusual restrictions the cost of the Prelims could be twice as much. A good first step is to work out a budget based on average costs per m2 to build an extension that is similar to yours. Size and Complexity of the Addition or RemodelSome cost factors here are obvious, such as the size of a porch or extra room. It is sent out blank (without any cost information) to contractors for them to price. The average house extension cost in London in 2019 is between £1,600 – £2,100 per m². This approach is great as it means you are not in the dark, and it gives you control over the cost of your extension, as well as allowing you to measure the impact of each of your decisions. To make sure that you understand the costs involved and get this right we suggest working out how much your extension should cost in 4 steps. An extension should be the best investment you ever make. But overwhelmingly the easiest place to have a big effect on the projected cost is in the fittings and finishes. Basement extensions cost on average between £3,500 – £5,000 per m². The detailed cost estimate that we looked at above, can now be turned in to a Schedule of Works which can be used to tender the work. Remember that your estimate of construction cost is part of the overall costs of your project. Or you may want to consider several options for the glass doors as part of the envelope that could cost either £5,000 or £15,000 depending on your choice.