Assume the worst

If you're buying a wreck you have to assume it's going to come with lots of problems, especially if it dates from the 1930s or before. An engineer's survey, as opposed to the building society one, will be the best money you've ever spent. You need someone to take off their jacket and look for signs of subsidence, dry and wet rot and other structural damage. In the past they used different methods of damp proofing (if at all) and had little or no insulation so you'll need to bring these up to date.

General electrics

Assume you'll have to rewire and replumb the whole house. It's not practical to rewire half a house - it's difficult to see what's behind walls and it's hard to link new and old wires. Also, nowadays, electricity companies have to sign off their work and they won't sign off anything that they didn't do.

No half measures

Generally, you shouldn't attempt to do things by halves. You may think half of a roof is okay and doesn't need replacing but when you take tiles off you realise there are problems with the part you thought was fine. You really do need to budget for doing whole jobs.

Agree the details

Couples should always discuss everything and never make decisions alone. It's common for the man not to be very interested until it comes to signing the cheque, and then any more expensive items they hadn't agreed on will cause a huge row. You need to decide on a budget and stick to it. If you hire designers you must both discuss the project with them.

Snug as bugs in rugs

Insulation is critical and you're better off spending money on this than on double glazing as lots of heat goes out through the walls and roof. I don't subscribe to the idea that you can heat the rooms you use and not the ones you don't. It's better to heat the whole house at a lower temperature than to blast a couple of rooms.

Spend wisely

The mistake that lots of people make is to buy expensive furniture, paint and wallpaper and feel they've done a classy renovation but this is just 10 per cent of an interior design task - most of the important work happens before that. People often go out and buy a fabulous couch, from a 2,000 sq ft showroom, only to find it looks ridiculous in their smaller home.

Prioritise the jobs

If you don't have enough money to renovate the whole house at once, start with the key rooms which are the kitchen, bathroom and bedroom because we all need to eat, sleep and wash. Before putting in a kitchen you must make the room sound - it's awful when people spend over £10,000 on installing a kitchen that soon has to be ripped out because the room is damp.

Know your numbers

Before you put in an offer or go to an auction get a local building contractor to go in and give you a ball-park figure so you know how much to put aside, be it £50,000 or £100,000. You're not looking for detailed estimate at this stage but a contractor will know what most things cost to make good.

Living on the site

If you need to live in the house while it is being renovated just remember that contractors won't treat your home like a house, they will treat it like a building site. There will be dust everywhere so get all the dirty work done first and live out if you possibly can.

Give the real budget

If you are hiring a designer it helps if they know your real budget. Often clients tell me they have, say, £60,000 to spend and they hold back £10,000 yet if I'd known at the beginning I would have done a totally different design. Another reason you need to be clear about your budget is that you don't want to cut corners at the tail end of a job because then you're dealing with all the visual elements. Savings made earlier on won't be as obvious.

Design for real life

People tend to spend their money in all the wrong areas. You need to go on the notion that you will live in the house and not in the garden looking at the house, admiring it. After rewiring, putting in a damp-proof course and insulation, a major consideration is how you will use the space now and in 10 years' time - when perhaps your family will have grown in number. Rooms in old houses often don't accommodate the way we live today so you'll probably need to rejig them to suit your lifestyle. Questions to ask yourself include is the kitchen too small or large (perhaps a coal bunker or former utility room could be turned into a kitchen), and do we have enough, or even too many, bedrooms. On one house we did the couple wanted an en suite bathroom and we sacrificed one of the four bedrooms to accommodate it as they said they would prefer that. Think about how you move around the house, what activities you do where and how you interact in the space. This helps you design the interior right down to where to place the sockets. I would advocate using an interior designer for the whole job but at least consider even a two-hour consultancy with a designer at the outset to discuss how to make the most of your space.

The big picture

The overall job is so important because your house is a statement of who you are. Within five seconds of entering your home people will get an impression of your character.

John Whyte and his partner Vivienne Lawson run Lawson Whyte Interior Design Ltd. They manage all areas of building jobs from start to finish. Tel. 01 456 4396 or www.lawsonwhyte.ie.