Millions of people spruce up their homes each year ready for selling, but if you are going to do it, make sure it pays, say Britain's top estate agents.

A survey commissioned by B&Q asked estate agents nation-wide which projects added the most value to the price of a property and which netted the best return on outlay if you DIY.

Key findings include that although the agents feel big home improvement projects, such as fitting a new kitchen or bathroom, add the most value to a property, the overall way a property looked was considered to be the most important thing if you are considering selling a house.

Virtually all the agents interviewed (86%) said that decorating and improving the whole presentation of a house added equally as much to the value of a property as fitting a new kitchen or bathroom. "People decide within eight seconds if they are going to buy a property or not" say the agents, so first impressions count.

Another key wisdom highlighted is that kitchens and bathrooms are the rooms that appeal the most to women. Many agents commented similarly, "if a kitchen is nice and the wife falls in love with it, it will sell the house. Kitchens and bathrooms are vital - women love their kitchens - they sell houses to women".

The survey also revealed that the smaller projects such as decorating not only added value to the price of the property, but are the ones that give the highest return on investment for the DIYer.

The projects that add the most value to a property:

• Extending with an extra reception room - average value added £9,500
• Adding a garage - average value added £8,000
• A kitchen refit - average value added £5,000
• A bathroom refit - average value added £3,000
• Decorating the whole house - average value added £3,000

The projects that give the highest return on outlay if you DIY:

• Decorating the whole house - giving a net gain of 220%
• Adding a garage - giving a net gain of 124%
• Piecemeal decoration - giving a net gain of 124%
• Refitting a bathroom - giving a net gain of 116%
• Refitting a kitchen - giving a net gain of 101%
• Adding wood/laminate flooring - giving a net gain of 50%

DIY vs professional

On average it costs twice as much to get a tradesman to do most projects as to DIY. The return on outlay if you DIY can be as high as 220% for some projects such as decorating.

For certain projects getting a professional in could even result in a loss. For example, DIYing piecemeal decoration could give you a return of 124%, as opposed to a loss of 37% if you get a professional in. And fixing up a wood floor or laying laminate flooring yourself could give you a return on outlay of 50% against a loss of 33% if a professional does it.

The 'eight second test' and 'kerb appeal'

First impressions count enormously. Giving your house ‘kerb appeal’ - making it look as attractive as possible - is vital. Agents reported viewings being cancelled because the buyer didn't like the look of the property from the outside - remember people decide within eight seconds if they are going to buy a property or not so make sure your house passes the test.

If you're going go do it, do it right

Estate agents were unanimous in one major piece of advice - if you DIY, make sure it is done well. In failing to recognise his or her limitations, the DIYer can find themselves with either a botched job that will detract from the value of their property, noted the estate agents, or worse still a job that has been inadequately and dangerously done.

The brand new 'You Can Do It - The Complete B&Q Step-By-Step Book Of Home Improvement' is a fully illustrated, easy to follow guide to home improvements containing expert advice on 234 projects and over 200 safety tips and tricks of the trade. Priced at £16.98, the book is available from B&Q stores nation-wide.

The survey was conducted by ICM earlier this year and 50 Estate Agents nation-wide were interviewed.