We paid for our daughter's loft conversion. She had a 'surprise' pregnancy and really wanted her children to have a bedroom each.
You need to contact professionals with regards to building regulations and submit your plans.
She took up her entrance hall, stair and landing carpet as they were fairly new.
The builder put some type of sheeting down and hoovered up any extra mess every day. She had a small skip on her drive for the four/five weeks they were there.
There was extra dust throughout the house. This was cleaned regularly. The scaffolding at the back of no the house did no damage whatsoever.
The builder's went into the house through the roof initially and kept going in through the front door to a minimum.
There were some days when they asked if she could go out during the day (she came to our house for the day). I think this was when the stairs went in.
She now has a large bedroom and en-suite so that the children can have a bedroom each (now a 4 bedroom property).
The windows open for ventilation in summer. The room is warm in winter. There's a radiator in the bedroom and one in the en-suite. It's her favourite room and she loves to go to bed early to spend time in there. She has lots of storage around the room (floor height) and a walk in wardrobe. There are lights which come on when she opens the storage doors.
The only negative thing is - the weather. Because there's no loft above her, she hears the wind and rain more. These recent storms have been particularly noisy.
She obviously had to decorate the new rooms and stairs. She matched the carpet the best she could to the rest of the house. There was some damage to bedroom ceilings which was touched up. She redecorated her old landing and stairs and entrance hall and had her old carpet refitted at the same time as her new carpet. She had to have all her doors in the house replaced with fire doors and these had to be painted.
The house was under 5 years old at the time and she needed permission from the house builder to alter it. She had submitted plans to the council for Building Regulations and this was signed off shortly after completing the conversion.
Within a couple of days of completion the scaffolding was down and the skip gone. She did a good spring clean of the house from top to bottom and now the house and garden are as they were before - she has a lovely home now.
You have to break eggs to make an omelette - so there will be a little disruption and dust along the way.
I'd go for a conversion - you might decide you don't want to move in the future. Her house feels much more spacious now. She says she'll never sell.