Hi --- VAT paid on materials used in connection with building a home can be reclaimed from the Inland Revenue (although a few items are excluded). However, this can only be done ONCE with any building project, which is why people building their own home will try to finish the project completely before reclaiming the VAT, as they
cannot reclaim VAT on later additions such as a garage or conservatory.
Therefore, if you are simple adding an extension to an already completed home, you cannot reclaim the VAT.