Nationwide Building Society estimated the potential for people to add value to their homes as the housing market revival gathers pace.
Converting a loft could add around 21% to a home's value, according to the building society's analysis using its own house price database.
Based on the average house price standing at £178,124 in the first quarter of 2014 according to Nationwide's house price index, this would mean a loft conversion could add another £37,400 onto the value of a home.
If the home owner decided to add another bedroom to their house, this could add around 11% to the worth of their property, equating to around £19,600, Nationwide found.
An extra bathroom could add around 5% or £8,900 to the value of a typical home. Boosting the floor space by 10% could add a similar amount of value to adding a bathroom.
The analysis follows reports which have pointed to the housing market continuing to spring back into life.
This week, a report from the Office for National Statistics said house prices are rising "strongly" in most of the UK.