I think that this is hugely variable - depends on what you are doing and what the state of the house is at the moment. There are lots of articles online on the topic weighing which improvements are best and which won't bring any extra... Before we moved to East Dulwich, we were considering having a new kitchen put into our old place. Got a few quotes, then decided to have a few estate agents in to see how much they thought it was worth spending/what it might add to the property value. Now of course, they do have a vested interest in trying to persuade you to sell now. We had a good number round though and they agreed that in the bracket of similar properties, it was wasn't worth it, as we wouldn't be able to get much more than what our place was currently valued at because of its size. Of course, if we wanted to hang onto it for another 5 years or so, then we may have been able to recoup the costs. (but as you can guess, we decided to put the place on the market instead, and moved here!)