You can try to fool yourself about this one, but you won’t fool anybody else.

We’ve seen the unfortunate end result of spending money on a lovely addition while leaving the old, cruddy part of the house as it always was.

Don’t do it! We know the marriage of old lived-in space and shiny new renovation doesn’t work.

Be realistic in the planning stage of your renovation — you’ll need to budget for bringing the whole house up to a reasonable level of “newness.” Many people who renovate are trying to save money, and actively avoid thinking about updating the “old” part. (It’s called sticking your head in the sand.)

But believe us, you’ll end up shelling out cash to fix it up sooner or later, and it will probably be sooner, because you can’t stand to look at that glaring discrepancy any longer. It will bug you every single day you live in that house — it would certainly drive us loco.

Luckily, there are some decor basics in minimizing that divide, and in making the house with a new addition look more unified. And the cost factor may be much lower than you think.

The first thing is to choose paint colour for the whole house — it must work together.

Depending on the size of your reno, you can decide on the same colour for both the new section and the older one, or you can choose a complementary colour that looks good with all the other tones in the house.

Don’t just paint the new section your favourite colour and expect it to look good with the existing house. It won’t.

Trim is also important —baseboards, trim around windows and trim in any other place should be consistent. If you have wood trim in the old part, you will find that matching that trim is sometimes difficult, and wood nowadays is expensive. If you are doing a large reno, you may find that it is actually cheaper to rip out the old trimwork (ouch!), and replace it with the same painted MDF trim throughout the house.

Another consideration is flooring. If your reno combines old and new space in the same room, you will need to put in new flooring for the whole space.

If the addition is a separate room separated from the old space, you can get away with a change of flooring (such as tile up against wood), as long as it is complementary, both in color and in mood.
Remember that a well-used wood floor will look strange up against a high-gloss marble tile, for example. Keep the feel of the whole house similar.

Metal fixtures, whether they be kitchen faucets, bathroom faucets or door handles, should be similar in look.

Keep the metal the same if possible. That is, use chrome throughout, or antique gold, but don’t use one metal and style in the new section and leave another metal and style in the old section.

Last, but not least, do not decorate the new section in a style that is vastly different to that in the older part of the house.

Strive to bring the old and new together in terms of style, mood and colour.

After all, if the discrepancy between old and new is the most visible thing about your house, your beautiful new space won’t shine the way it should.

Tammy Schnurr and Jeffrey Fisher are hosts of Arresting Design on W Network. Tammy is an interior decorator. Jeffrey designs home furnishings and bedding through his company Jeffrey Fisher Home.