Extending a property

[Mermaid36]

We are currently discussing (with my mum) whether my she should sell up and use the money from her house sale to extend our house and come and live with us (it was her idea)

The plan would be to put a 2 storey extension on our 3 bedroom semi, comprising of a large kitchen extension, with a double bedroom and en-suite above it.

We have the room on our land (1/4 of an acre of garden etc), but we're not sure whether it would increase the value of the house enough (e.g if the build cost us £50k, would it add £50k to the value of the house?). We can't even compare house prices down our road, because of the different types of houses - they range from 2 bed terraced bungalows to a 5 bed equestrian property with 3 acres, stables, kennels and a sand paddock...

Does anyone know of how you can work out whether it would be worth it? Is it a case of a valuation from an estate agent (a la Homes Under the Hammer)?

[APlaceOnTheCouch]

You could ask an estate agent or a surveyor (although the latter prefer the build to be completedcompleted first). The tax on houses with granny flats is changing so you will be taxed on both when you sell. It's probably worth bearing that in mind when you get your architect to draw up plans, and when you look at your figures.

If they are taxed separately, it might be worth considering a separate build rather than an extension; or a park home (if the planners would approve).